Search

Polydimethylsiloxanes with improved mechanical properties that can be processed by 3D printing are in high demand for scientific and practical applications. In our article, we proposed the synthesis of new PDMS copolymers with urethane and triazole fragments using the CuAAC reaction mechanism, as well as 3D printing with the obtained copolymers. Two types of copolymers, with molecular weights of 3000 and 6000 Da of PDMS block length, were prepared and characterized by GPC, IR spectroscopy, TGA, DSC, TMA, SAXS, and rheological measurements to determine their physicochemical properties. The synthesized copolymers were found to be suitable for processing by extrusion 3D printing. This demonstrated the ability to 3D print macroscale models of varying shapes and complexity. The resulting materials retained their printed shape over time. SYNOPSIS (Word Style "SN_Synopsis_TOC"). If you are submitting your paper to a journal that requires a synopsis, see the journal's Instructions for Authors for details. [Display omitted] • Copolymers based on PDMS and a urethane block were synthesized using the CuAAC reaction mechanism. • The resulting copolymers are fully characterized. • 3D printing using the obtained copolymers was demonstrated. • 3D printed membranes return to their original shape in a shape recovery test. [ABSTRACT FROM AUTHOR]

Background Context: Cutibacterium acnes (C. acnes) is a gram-positive facultative anaerobe found in the deep sebaceous follicles of the skin on the shoulder and back. C. acnes has been increasingly recognized as a pathogen in spinal surgical site infection (SSI) especially in the presence of instrumentation.Purpose: This study assesses whether a silver carboxylate-doped titanium dioxide-polydimethylsiloxane (TiO2-PDMS) coating can decrease C. acnes adherence and biofilm formation on PEEK and four other commonly used spinal implant materials, stainless steel, cobalt chromium, titanium, and titanium alloy.Study Design: We compared the adherence of C. acnes over 24 hours between uncoated, 95:5 TiO2 to PDMS ratio with 10× silver carboxylate coating and a 100% silver carboxylate coating on each implant material, which were uniformly saw cut and sterilized. Implants were then subjected to scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM).Methods: Samples were coated using 95:5 TiO2-PDMS 10× silver carboxylate, 100% silver carboxylate, or left uncoated. C. acnes was applied onto the samples and allowed to adhere for periods of 4, 8, 12, 16, or 20 hours. Nonadherent bacteria were then washed from the samples. These samples were then allowed to continue incubating for a total of 24 hours. SEM and confocal laser scanning microscope were used to visualize all samples for the presence of biofilm and quantification of C. acnes adherence at each time point.Results: The 95:5 TiO2-PDMS 10× silver carboxylate coating was able to significantly decrease C. acnes adherence on PEEK after 8, 12, 16, and 20 hours of adherence. No statistical difference was found between the 95:5 TiO2-PDMS 10× silver carboxylate coating and the 100% silver carboxylate positive control. We previously observed extensive C. acnes biofilm formation on uncoated PEEK, but none on PEEK coated with either the 95:5 TiO2-PDMS 10× silver carboxylate or 100% Ag coating . Furthermore, no biofilm formation was observed on stainless steel, cobalt chromium, titanium, and titanium alloy coated with 95:5 TiO2-PDMS 10× silver carboxylate or 100% Ag coating.Conclusion: A 95:5 TiO2-PDMS 10× silver carboxylate coating decreases C. acnes adhesion and prevents biofilm formation on PEEK and other common orthopedic implant materials.Clinical Significance: A 95:5 TiO2-PDMS 10× silver carboxylate coating may help decrease spinal SSI due to C. acnes, especially in procedures with instrumentation. [ABSTRACT FROM AUTHOR]

[Display omitted] • An extremely simple emulsion gel (EG) system is constructed by glutamic acid (Glu) and carefully engineered polysiloxanes (AESi). • The formation of EG did not need the addition of extra surfactants. • The stability of EG was provided by the in situ formed AESi/Glu supramolecular complex. Emulsion gels (EGs), combined the advantages of both emulsions and gels, have attracted much attention in colloid chemistry. However, the preparation of EGs is usually complicated, which greatly hinders their development. Herein, we prepared a polydimethylsiloxane (PDMS) derivative which bears poly (ethoxylated ether) (PEO) segments at the ends and a few alkylamine groups on the side (denoted as AESi hereafter). When being mixed with an acidic amino acid (glutamic acid, Glu) in water, the amine groups of AESi were protonated, leading to an abrupt increase of its solubility. The AESi/Glu complex acts as a supramolecular amphiphile, which can form capsules in water. It can also stabilize excess AESi to form self-confined emulsions. In high loading of AESi, the emulsion droplets stack closely to form highly stable EGs. The EGs possess good viscoelasticity and are tunable by changing temperature or adding inorganic salts. By performing control experiments, structural features of the PDMS derivative and organic acid needed for the construction of EGs have been clarified. The strategy presented in this study provides new opportunity for the preparation and applications of EGs. [ABSTRACT FROM AUTHOR]

Silicones (i.e. crosslinked poly(dimethylsiloxane), PDMS) are commonly used material for microfluidic device fabrication. Nonetheless, due to the uncontrollable absorption of small hydrophobic molecules (<1 kDa) into the bulk, its applicability to cell-based drug assays and sensing applications has been limited. Here, we demonstrate the use of substrates made of silicones bulk modified with a poly(ethylene oxide) silane amphiphile (PEO-SA) to reduce hydrophobic small molecule sequestration for cell-based assays. Modified silicone substrates were generated with concentrations of 2 wt.%, 9 wt.% and, 14 wt.% PEO-SA. Incorporation of PEO-SA into the silicone bulk was assessed by FTIR analysis in addition to water contact angle analysis to evaluate surface hydrophobicity. Cell toxicity, absorption of small hydrophobic drugs, and cell response to hydrophobic molecules were also evaluated. Results showed that the incorporation of the PEO-SA into the silicone led to a reduction in water contact angle from 114° to as low as 16° that was stable for at least three months. The modified silicones showed viability values above 85% for NIH-3T3, MCF7, MDA-MB-468, and MDA-MB-231 cell lines. A drug response assay using tamoxifen and the MCF7 cell line showed full recovery of cell toxicity response when exposed to PDMS modified with 9 wt.% or 14 wt.% PEO-SA compared to tissue culture plastic. Therefore, our study supports the use of PEO-SA at concentrations of 9 wt.% or higher for enhanced surface wettability and reduced absorption of small hydrophobic molecules in PDMS-based platforms. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The porous PDMS (P-PDMS) film was fabricated by NaCl template method. • The P-PDMS film achieved an average 18.7 ℃ lower than the sub-ambient. • The P-PDMS film has a water contact angle of 132.92°. Passive daytime radiative cooling (PDRC) is a green and energy-free passive cooling method by reflecting sunlight and radiating heat into the cold outer space through atmospheric transparent windows (ATW). High reflectivity and high emissivity are two vital factors affecting the cooling performance. In this work, an environmentally friendly porous polydimethylsiloxanes (PDMS) radiative cooling film was fabricated, which has 73.3 % solar reflectance (0.3–2.5 μm) and 99.7 % infrared emissivity (8–13) μm. Thus, the sample displayed a remarkable PDRC property by yielding an average temperature drop of 18.7 ℃ compared to the sub-ambient temperature at the solar intensity of 769 W/m2. At the same time, the film with hydrophobicity (132.92°) can decrease pollution caused by dust, which is significant for prolonging life and maintaining the performance of these films. This technique is simple and economical, and has the prospect of large-scale commercial application. [ABSTRACT FROM AUTHOR]

[Display omitted] • ● A cycloaliphatic epoxy-functionalized polydimethylsiloxane (PDMS-CE) was synthesized. • ● PDMS-CE modified epoxy (EP/PDMS-CE) thermosets were fabricated. • ● EP/PDMS-CE thermosets showed a slight increase in T d5% and T g. • ● EP/PDMS-CE thermosets showed a significant improvement in toughness. • ● PDMS-CE is a promising and all-purpose modifier for epoxy thermosets. Polydimethylsiloxane (PDMS) are known as a class of efficient modifiers for epoxy thermosets, but the simultaneous improvement in thermal stability, thermomechanical and mechanical properties remain a challenge. Herein, we report a cycloaliphatic epoxy-functionalized polydimethylsiloxane (PDMS-CE) with a designed epoxy value for comprehensive modifications of diglycidyl ether of bisphenol A (DGEBA)/methylhexahydrophthalic anhydride (MeHHPA) thermosets. Compared to neat epoxy thermoset, the 4 wt% PDMS-CE modified epoxy thermoset showed a 79 %, 120 % and 503 % increase in flexural strength, impact strength and fracture toughness, respectively, as well as a slight increase in the initial thermal decomposition temperature (T d5%) and glass transition temperature (T g), and a desirable decrease in the dielectric constant and water absorption rate. This comprehensive modification performance was caused by the combined effects of crosslinking density improvement, rigid cycloaliphatic structure, as well as the flexible PDMS chains. [ABSTRACT FROM AUTHOR]

We present an experimental investigation into the binary phase behaviour of carbon dioxide and three different linear polydimethylsiloxanes (PDMS) with molecular weights of 4800 g/mol, 11000 g/mol and 18000 g/mol. Experiments were carried out at 25 °C, 40 °C and 60 °C and at pressures of up to 30 MPa. Solubilities were measured with the help of a high pressure view cell using two different techniques, the observation of cloud points, and a static analytic method based on sampling under phase equilibrium conditions. Rather low molecular weight polydimethylsiloxanes were chosen to close the existing data gap regarding the behaviour of these compounds with carbon dioxide. All experiments in the present work were carried out under isothermal conditions. Hence, diagrams of the p- x type are used for displaying the measured data at constant temperatures. • Phase equilibrium data was measured for three different polydimethylsiloxanes and CO 2. • Two different methods were applied, the cloud point method and an equilibrium method. • Data are presented for 25 °C, 40 °C and 60 °C and in a pressure range of up to 30 MPa. [ABSTRACT FROM AUTHOR]

Abstract We present a self-discretization and zero-water-loss microfluidic digital PCR (dPCR) device to enable low-cost and robust quantitative nucleic acid assays. In this device, a thin void is integrated beneath the reaction chamber array. By utilizing the permeability of polydimethylsiloxane (PDMS) film, the integrated void serves a dual function: vacuum "accumulator" and hydration "reservoir". The combination of pre-stored pumping energy and water compensation for evaporation loss enables simple, robust and reliable single-DNA-molecule amplification and detection in 10,000 reactors of picoliter volume. Compared to the conventional degassing PDMS pumps, the vacuum accumulator exhibits superior performance due to more vacuum storage and shorter diffusion distance. We also evaluated the performance of the embedded hydration layer in suppressing evaporation loss at elevated temperatures, and verified that zero-water-loss could be achieved for all reaction chambers in our dPCR chip during thermal cycling. By performing quantitative detection of T790M DNA from 10 to 104 copies/μL, the proposed dPCR chip demonstrated high accuracy and excellent performance for the absolute quantification of the target gene with a dynamic range of 104. The simplicity and robustness of our dPCR chip make it well suited for low-cost molecular diagnostic assays under resource-limited settings. Graphical abstract Image 1 Highlights • A self-digitization and zero-water-loss microfluidic digital PCR (dPCR) chip is developed. • A dual function void is integrated in the dPCR chip. • The integrated dual function void serves as vacuum accumulator and hydration reservoir. • Our dPCR chip can provide low-cost and robust quantitative nucleic acid assays. [ABSTRACT FROM AUTHOR]

Abstract Vertically aligned (VA) and open-ended carbon nanotube (CNT) arrays filled polydimethylsiloxane (PDMS) composite membrane was fabricated, characterized, and evaluated for pervaporative recovery of butanol from acetone-butanol-ethanol (ABE) fermentation broth. The VA CNT (open-ended)/PDMS membrane displayed various advantages over homogeneous PDMS membrane, since the VA CNT (open-ended)/PDMS membrane demonstrated a simultaneous improved butanol flux and separation factor, which was the result of higher butanol solubility and diffusivity of this membrane. Both butanol flux and separation factor showed a sharp enhancement with increasing feed temperature (30–80 °C), and with increasing feed butanol concentration (5–25 g/L). The maximum total flux and butanol separation factor of the VA CNT (open-ended)/PDMS membrane reached 1093.7 g/m2 h and 37.6 at 80 °C, respectively. The composite membrane showed a stable performance for long-time continuous operation with fermentation broth for biobutanol production. Overall, the VA CNT (open-ended)/PDMS membrane showed higher butanol flux and selectivity than homogeneous PDMS membrane, and has great potentials for butanol separation from ABE fermentation. Graphical abstract fx1 Highlights • The vertically aligned and open-ended CNT/PDMS membrane was fabricated. • Pure butanol solubility and diffusivity were increased compared to homogeneous PDMS. • VA CNT (open-ended)/PDMS membrane showed high PV performance for recovering butanol. [ABSTRACT FROM AUTHOR]

Abstract Mixed-gas sorption of CO 2 -CH 4 mixtures in rubbery polydimethylsiloxane (PDMS) at 35 °C demonstrated that the presence of CH 4 changed the behavior of CO 2 sorption and vice versa. This mutual interaction indicated that gases in mixtures do not sorb independently in rubbery membranes. Moreover, we observed that at increasing pressures the interaction between PDMS and CO 2 -CH 4 mixtures enhanced the solubility selectivity of PDMS. Mixed-gas solubility coefficients of CH 4 in PDMS were lower than 0.5 cm3(STP) cm−3 atm−1. To accurately measure these values, a new sorption system was designed, constructed, and optimized for low solubility coefficients; an operator-friendly approach to mixed-gas sorption experiments is also discussed in this work. CO 2 -CH 4 mixed-gas diffusivity trends were evaluated from Maxwell-Stefan model fitting of mixed-gas permeation and sorption data. The analysis of both mixed-gas diffusion and sorption data demonstrated that CO 2 /CH 4 mixed-gas permselectivity of PDMS was mainly influenced by CO 2 sorption. In mixtures, CH 4 diffusion coefficients increased with higher volumetric CO 2 concentration, whereas the CO 2 diffusion coefficient was essentially concentration independent in both pure- and mixed-gas environments. Graphical abstract fx1 Highlights • A new mixed-gas sorption system with optimized volumes for low-solubility detection. • CO 2 -CH 4 mixed-gas sorption in rubbery PDMS deviates from pure-gas trends. • Enhanced CO 2 /CH 4 solubility selectivity was caused by mixture effects and pressure. • CO 2 induced phenomena increased CH 4 diffusion coefficient. [ABSTRACT FROM AUTHOR]

Abstract Because of the wide practical applications of soft materials, the surface contact and adhesive behaviors need to be comprehensively understood. Here, we systematically investigated the effect of bulk viscoelasticity and surface wetting on the dynamic behavior of contact and adhesion of soft polydimethylsiloxane (PDMS) surfaces. Experimental results showed that during the indentation process, the relation between loads and contact radius were close to the Johnson-Kendall-Roberts (JKR) mode, but the load-penetration curves presented a roughly linear dependence with increasing preloads transferring from the JKR to Hertz mode; the detaching process exhibited a pronounced "stick-split" behavior, where the spherical probe first stuck to the soft PDMS without decreasing the contact area, and then the crack of the contact edge opened and split, providing high adhesive forces far exceeding the JKR prediction. The introduction of liquids between the probe and soft PDMS strongly decreased the contact area, reduced the stick time, and weakened the dry adhesive strength depending on the surface tension. The internal friction induced by the segmental motion of long-chain molecules and the interfacial resistance of liquid were suggested to be responsible for these phenomena. Highlights • The indentation relation of load-contact radius is close to JKR mode, the load-penetration transfers linearly to Hertz mode. • Detachment on PDMS exhibited a pronounced "stick-split" behavior, with the adhesive forces far exceeding the JKR prediction. • Wedged liquids between the probe and PDMS decreased contact area, reduced stick time, and weakened dry adhesive strength. • Internal friction of the long-chain molecule motion and interfacial resistance of the liquid were responsible for these results. [ABSTRACT FROM AUTHOR]

Abstract Biofuels separation using membranes becomes one of the research focuses in the field of renewable energy. In this study, a series of mixed matrix membranes (MMMs) with defect-free active layer around 1 µm thickness were elaborately prepared through interfacial synthesis for ethanol permselective pervaporation. Polydimethylsiloxane (PDMS) was employed as polymer matrix, which adjusted the nucleation of MOF precursors to in situ generate ZIF-8 nanoparticles. Within the active layer, the resultant ZIF-8 nanoparticles provided the preferential pathways for ethanol due to their ultrahigh adsorption capacity and super-hydrophobicity. Moderate aggregation could form the relatively continuous diffusion pathways. This approach rendered the uniform dispersion of ZIF-8 nanoparticles within PDMS matrix and their excellent compatibility. The ZIF-8 nanoparticles endowed the membranes with enhanced ethanol affinity, hydrophobic property, and thermal stability. More importantly, the ZIF-8 nanoparticles substantially reduced the permeation energy barriers of the membrane for penetrants. The membranes displayed the simultaneous increase in permeation flux and separation factor when utilized for ethanol recovery from aqueous solution, revealing the desirable anti-tradeoff effect. Particularly, the resultant membrane exhibited a superior pervaporation performance with relatively high permeation flux (1778 g · m-2 · h-1) and comparable separation factor (12.1) in separating 5.0 wt% ethanol aqueous solution at 40 °C. Graphical abstract fx1 Highlights • Mixed matrix active layer around 1 µm thickness prepared via interfacial synthesis. • Uniformly dispersed ZIF-8 nanoparticles were in situ formed within PDMS matrix. • ZIF-8 nanoparticles created the preferential paths for ethanol rather than for water. • Introducing ZIF-8 nanoparticles addressed facilely trade-off effect in PV membrane. • ZIF-8 nanoparticles notably reduced the permeation energy barriers for penetrants. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the efficacy of urethral bulking agents for stress urinary incontinence (SUI) in the setting of prior failed sling.Methods: This is a retrospective review of patients who underwent urethral bulking agent injections for a primary complaint of SUI following prior failed sling surgery. The outcomes assessed were patient reported improvement, need for further interventions for incontinence and validated questionnaires. Values for questionnaires were obtained from the patient's preprocedure visit, at the first visit following their last injection and at their most recent visit within our system.Results: Over the study period, 73 patients underwent urethral bulking agent injection following failed sling. Thirty-eight patients received Macroplastique injections and 35 had collagen injections. On average, patients underwent 2.6 injections. Seventy-one percent of patient reported at least partial symptom resolution at first postinjection follow-up. Validated questionnaire responses also improved at short-term follow-up (mean difference in American Urological Association Symptom Index-3.8, Michigan Incontinence Symptom Index-5.1, P <.01). Forty patients had long-term follow-up data available (mean 39.6 months postinjection). Statistically significant improvement persisted on the stress incontinence and quality of life domains of the validated questionnaires.Conclusion: In our cohort of patients with persistent or recurrent SUI following urethral sling procedure, 71% experienced short-term improvement or resolution of symptoms following urethral bulking agent injections, with SUI-specific improvement persisting at an average of 35 months in patients with available data. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cell viability of PC12 was reduced at high concentrations of liquid PDMS. • Morphological alterations were detected at high concentrations of liquid PDMS. • PDMS and silicone rods did not induce the expression of apoptotic markers in PC12. • Liquid PDMS formed a surface film over medium. • Silicone rods are biocompatible on PC12 cells, thus useful in cochlear implants. Abstract Cochlear implants, the only way to recover from severe/profound hearing loss, may cause adverse effects, among which reactions to silicone materials coating implant electrodes, leading to apoptosis and necrosis of spiral ganglion cells. Our aim was to evaluate whether three polydimethylsiloxane (PDMS) compounds (hexadimethylsiloxane, octamethyltrisiloxane, decamethylcyclopentasiloxane) used in silicone rods could exert toxic effects on an in vitro neuronal cell model (PC12). Cell viability, morphology and mRNA expression levels of apoptotic markers were evaluated on PC12 cells at different PDMS dilutions up to 6 days of exposure. The results showed that at the highest concentrations tested cell viability was reduced by hexadimethylsiloxane and octamethyltrisiloxane at all times of exposure, but only from 72 h onwards by decamethylcyclopentasiloxane. The number of neurites per cell was not affected by hexadimethylsiloxane, but was significantly reduced from 24 h onwards by octamethyltrisiloxane and decamethylcyclopentasiloxane. Neurite length was reduced by hexadimethylsiloxane only at 24 h, and by octamethyltrisiloxane and decamethylcyclopentasiloxane at all exposure intervals. In controls exposed to silicone or glass rods cell viability was reduced only after 24 h, but neurite number and length was never reduced at any exposure interval. Biomolecular investigations showed that apoptotic markers did not change in any experimental condition, suggesting that PDMS are biocompatible. The reduction of cell viability and neurite number and length caused by exposure to these compounds was probably caused by a PDMS surface film formed over the cell medium, preventing air exchange, and not by the release of cytotoxic molecules. [ABSTRACT FROM AUTHOR]

Abstract This study aimed to evaluate the effect of poly(dimethylsiloxane) on the mechanical properties of chitosan-alginate (CA) polyelectrolyte complexes (PECs) with potential application as wound dressing biomaterials. For that purpose, different amounts of poly(dimethylsiloxane) were incorporated during the formulation of the PECs. Results showed that the highest tensile strength was observed when using 0.1 g of poly(dimethylsiloxane) per gram of PEC (CAS10). This formulation was also non-hemolytic, capable of inducing thrombus formation to potentially reduce bleeding, and additionally presented high stability when exposed to physiological fluids and/or conditions simulating patient bathing. To improve its wound healing capacity, this formulation was loaded with thymol and beta-carotene (anesthetic, anti-inflammatory and antioxidant compounds) by the supercritical carbon dioxide impregnation/deposition (SSI/D) method at 250 bar and 45 °C for 14 h and at two depressurization rates (5 and 10 bar/min). The PECs were also loaded by conventional impregnation in solution for comparison purposes. Higher bioactive loadings, of 1.8 ± 0.2 and 1.3 ± 0.03 μg per milligram of PEC for thymol and beta-carotene, respectively, were observed when using SSI/D and a higher depressurization rate (10 bar/min). These values do not correspond to the maximum loaded amount of each bioactive, which were strongly retained in the PEC structure due to favorable bioactive-polymer interactions, originating matrices that should present a more sustained release during in vivo applications. Highlights • PDMS, chitosan and alginate were combined to obtain wound dressings. • The effect of PDMS on the mechanical properties the dressings was analyzed. • The highest tensile strength was observed for 0.1 g of PDMS per gram of CA. • The formulation was non hemolytic and stable in physiological fluids. • Thymol and beta-carotene were incorporated to the dressings to improve bioactivity. [ABSTRACT FROM AUTHOR]

Highlights • Response rule of cyclic and linear dimethylsiloxanes in FID was preliminarily explored. • An accurate quantitative method for compounds in PDMS 200 fluid was established by GC-FID. • Comparison between the new method and the three traditional methods was conducted. Abstract PDMS 200 fluid (the mixture) was used as standard for quantification of linear dimethylsiloxanes (L5-L16) in environmental matrices. However, the quantification of individual dimethylsiloxane in PDMS 200 fluid by GC-FID was not established or detailed described in many real studies. To solve this problem, we did this research and the principal results were as follows: fifteen compounds in PDMS 200 fluid, including D7, L5 to L16 (12 linear dimethylsiloxanes) and 2 unknown compounds, were identified using GC–MS. Retention indices (RI) of L8 to L16 were first given. Meanwhile, we found that the "effective carbon number (ECN) concept" was applicable for responses of dimethylsiloxanes in FID. Based on GC-FID, a new quantification method for compounds in PDMS 200 fluid was established, detailed described and used to calculate the content of individual dimethylsiloxane in PDMS 200 fluid. Compared with the results from external standard method, internal standard method and normalization method, the new quantification method was more accurate and stable, especially for D7 at low content. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • DEA is constructed to achieve out-of-plane actuation without requiring prestrain. • NH 2 -PDMS elastomer is synthesized and sandwiched by two asymmetric electrodes with distinct mechanical properties. • DEA diaphragm takes periodic vibration and exhibits a large flection angle of 26.3°. • DEA exhibits well controlled electromechanical performance by driving voltage or frequency. Abstract This study presents a novel and facile strategy to construct prestrain-free dielectric elastomer (DE) film with large out-of-plane actuation. An extremely soft elastomer of amino functionalized poly(dimethylsiloxane) (NH 2 -PDMS) with thickness of ∼446 µm was employed as dielectric matrix, which was sandwiched between two asymmetric PDMS electrodes with distinctly designed mechanical properties. Electromechanical coupling factor (ECF, dielectric constant/elastic modulus) of the DE film increased with amino density coupled into dielectric matrix, providing a strategy to construct a DE actuator (DEA) with large displacement under low electric field. The thin, soft electrode was made of an off-ratio polymer of PDMS doped by conductive graphite microflakes, while the thick, stiff electrode was made of completely cured PDMS elastomer doped by conductive graphite microflakes and Ag nanoparticles. The film thicknesses, Young’s moduli, and surface resistances were 54.1 µm, 9.21 MPa, 1.02 kΩ/cm2 for the soft electrode, and 166.7 µm, 87.5 MPa, 0.13 kΩ/cm2 for the stiff electrode, respectively. The prepared DEA diaphragm exhibited well controlled electromechanical properties by driving voltage or frequency, and a high flection angle of 26.3° at an extremely low electrical field of 8.8 V/μm. Thus, it can be used as intelligent valve flap/pump for microfluidic device and artificial muscle with minimized energy assumption activated by low voltage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The conductive composites were prepared by simply blending graphene and PDMS-urea using THF as solvent. • The conductivity of the composite film containing 12 wt% graphene reaches 81.5 S/m. • The composite has excellent self-healing capability, assisted by the THF vapor. Abstract Flexible and self-healing conductive materials are highly desired in the development of soft electronics due to their wide applications. Here we report the preparation of a flexible and self-healing conductive composite by simply blending few-layered graphene with poly(dimethylsiloxane)-containing urea segmented copolymer (PDMS-urea) using THF as solvent. The obtained composite materials show excellent electrical conductivity and self-healing capability. The relationship between the conductivity of the composite film and the graphene weight ratio was investigated and the conductivity of composite containing 12 wt% graphene reaches 81.5 S/m. Based on the balanced flexibility and conductivity, the solvent vapor-induced self-healing and material recyclability studies were performed on a 10 wt% graphene doped composite. The severed sample can be readily healed by exposing it to THF vapor at room temperature and the recovery of electrical conductivity comes up to around 95%. Due to the excellent self-healing capability, the composite film cut into tiny pieces can be recycled assisted by THF vapor with only slightly losing its electrical conductivity. [ABSTRACT FROM AUTHOR]

The capability to detect nitro-based explosives from their vapor is often limited by their low vapor pressure. One approach for overcoming this limitation is to use a solid-state pre-concentrator. The sorption and desorption of nitroaromatic vapors by poly(dimethylsiloxane)-based (PDMS) films fabricated from three different molecular weights of hydroxy-terminated poly(dimethylsiloxane) (HO-PDMS) macromonomers has been investigated. It was found that independent of macromonomer molecular weight, all the PDMS films were able to sorb nitro-based explosive analyte. However, for PDMS films of similar thickness, those formed from the lowest molecular weight macromonomer sorbed the least analyte and had the poorest retention capability. Atomic Force Microscopy (AFM) suggested that at least a proportion of the analyte was adsorbed onto the surface of the PDMS film formed from the low molecular weight macromonomer. PDMS films from the higher molecular weight macromonomers sorb more analyte with the vapor diffusing into the bulk of the film. PDMS films formed from the 750 cSt macromonomer were found to have the best analyte sorption and retention properties. The best pre-concentrator film was determined to increase the available analyte for vapor detection by up to 2 orders of magnitude. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fabrication of silica pillar arrays from a self-assembled PS- b -PDMS. • GISAXS and SEM observations of transient morphology. • Solvent selectivity used for spin-coating dictates the final morphology. • The regularity of the final morphology is validated by optical responses. • The obtained nanostructure can be applied as a reproducible SERS (surface-enhanced Raman spectroscopy) substrate. Abstract We discuss the formation of perpendicular cylinders from polystyrene- block -poly(dimethylsiloxane) (PS- b -PDMS), which were used to fabricate silica (SiO 2) pillar arrays with an aspect ratio of 5. The solvent used in spin-coating solutions to form the initial films played an important role to lead the final morphology of the cylinders after solvent annealing. Tetrahydrofuran, a selective solvent for the major PS block, trapped PDMS spheres in isolation, opening a route to form highly aligned perpendicular cylinders after an induction period. Meanwhile, cyclohexane, a non-selective solvent, connected PDMS domains to some extent and provided a different route through which moderate regularity was achieved with gradual improvement. The transient morphological changes of the cylinders were precisely investigated using grazing-incidence small-angle X-ray scattering and scanning electron microscopy. The alignment of the final morphology of the cylinders was validated by reflectance and optical ellipsometry measurements. Oxygen plasma was used to completely remove organic substances and convert PDMS to SiO 2 , providing a platform suitable for various applications. As an example, a surface-enhanced Raman spectroscopy (SERS) platform was obtained by depositing gold on a perpendicular silica array. This platform exhibited substantial SERS enhancement using Rhodamine 6G as a probe molecule. Identical enhancements were observed throughout the platform, which was attributed to its uniform nanostructures. [ABSTRACT FROM AUTHOR]

Formation and accretion of ice on the leading edge surface of aircrafts wings may lead to disasters. The current de-icing system for aircraft will build up weight, increase energy consumption and add complexity to the aircraft systems. Development of icephobic coatings is a potential solution to prevent ice formation and/or reduce accretion on the critical surface of aircraft. Icephobic coatings based on poly(dimethylsiloxane) (PDMS) with modification by fluorosilane and incorporation of silica nanoparticles have been fabricated. The hydrophobicity of the coatings has been measured in normal conditions with atmospheric pressure and room temperature, showing improvement of hydrophobicity by the fluorination of PDMS and incorporation of silica nanoparticles. The water droplet icing behaviour shows better anti-icing performance for fluorinated PDMS (F-PDMS)/silica coatings with a rough surface. The ice adhesion strength test results show that F-PDMS coatings without silica nanoparticles have lower ice adhesion strength implying better de-icing performance. The wettability of the coatings was also measured at reduced pressure and temperature, to study the mechanism of higher ice adhesion strength of F-PDMS/silica coatings comparing with F-PDMS based coatings. For the design and fabrication of icephobic coatings, compromise on the roughness induced hydrophobicity may become a critical requirement to avoid mechanical interlock between the ice and the rough surface. [ABSTRACT FROM AUTHOR]

A method for the fabrication of homogeneous and well-dispersed polymeric nanofiber composites was investigated. Nanofiber fillers can be used to produce polymeric nanocomposites by mixing the fillers to base polymers, eventually enhancing the mechanical property of the matrix polymers. To produce such composites, nanofibers were usually sandwiched by molten matrix polymers at high temperature before molding. The traditional so-called sandwich method, however, was found to produce rather biased and inhomogeneous composites due largely to the solid entanglement of the nanofibers. In this work, unwoven polymer nanofibers were synthesized through electrospinning by controlling the electrostatic repulsion of the nanofibers. We modified the electrospinning apparatus for the direct synthesis of homogenous composites: nanofibers were electrospun and directly ejected from the electrospinning syringe to the matrix polymer solution (not in a solid state), where a regular metal electrode plate was replaced by an optimized metal container containing the base polymer solution. It was found that this new fabrication method could realize homogeneous mixing of the nanofibers that were eventually uniformly dispersed in the polymer solution. Poly(vinyl alcohol) (PVA) was used for nanofibers and polydimethylsiloxane (PDMS) was used for polymer matrix. The field emission scanning electron microscopy (FE-SEM) revealed the homogeneous and well-dispersed PVA nanofibers in the resulting PDMS composites. The composites also presented higher mechanical properties as compared with the composites fabricated by the traditional sandwich method. [ABSTRACT FROM AUTHOR]

A multiple headspace extraction experiment coupled to gas chromatography (MHE-GC) is used for the classification and qualification of different mesoporous silica (MPSi) materials used for drug delivery. In this MHE experiment, a pure liquid solvent probe is fully evaporated in a sealed headspace vial in the presence of the MPSi sample, leading to a gas-solid partitioning that is theoretically described. The obtained results matched with the known characteristics of the studied samples, such as adsorption capacity due to differences in porosity and passivation treatments. Moreover, it proves the effectiveness of a poly dimethyl siloxane (PDMS) coating treatment over a thermal one in reducing the specific interactions of the MPSi. In addition, it evidences the important role of confinement effects when the pore diameter is close to the microporosity range. Finally, a simple experiment for fast screening is proposed by comparison of the results obtained for four different probes used as a mixture. [ABSTRACT FROM AUTHOR]

Based on commercially available 3-Aminopropyl (diethoxy)methylsilane new alkoxysilane with functional aminophosphonate group - diethyl (2-((3-(diethoxy (methyl)silyl)propyl)amino)propan-2-yl)phosphonate were synthesized and characterized. Obtained functional alkoxysilane were transformed to tetrasiloxane in active medium in the presence of acetic acid and then copolymerized with octamethylcyclotetrasiloxane (D4). The chemical structure of the resulting polymer was studied and confirmed by a combination of physical methods, namely, 1 H, 13 C, 31 P and 29 Si NMR, GPC, and IR spectroscopy. The thermophysical and rheological properties of the polymer were also studied. [ABSTRACT FROM AUTHOR]

Highlight • A novel color filtering device based on a hybrid MEMS-elastomer configuration and SPR was proposed. • The elastomer was strained by the symmetrically arranged planar MEMS. • A sequential modulation was induced by the strained elastomer from 0% to 35.91%. • The SPR modulations were based on only one nanoengineered component. • The isotropic strain distribution on elastomer was confirmed within radius of 21.2 μm. Abstract In this study, a microelectromechanical system (MEMS)-based color filtering device comprising a silicon-on-insulator MEMS, an elastomer, and an array of metallic nanostructures with adjustable surface plasmon resonance (SPR) modulation was proposed. The MEMS stretched the elastomer suspended above it, which modified the arrangement of the metallic nanostructures on the elastomer. Consequently, the SPR could be tuned under various MEMS operating conditions using a single fundamental design. An optimized hybrid MEMS-elastomer configuration was obtained with a maximum strain of 35.91% through evaluations done with three parameters in the MEMS and three parameters in the elastomer. The SPR modulation was demonstrated using an example involving color filtering and switching among the three primary colors in the visible range. In addition to design optimization, the asymmetrical strain distribution in the elastomer and its influence on SPR modulation were studied through comprehensive simulations and analyses. [ABSTRACT FROM AUTHOR]

Graphical abstract PDMS surface tethered with high-density PHEMA brush exhibits excellent protein and platelet resistance and limits cell adhesion and growth. Gelatin conjugation on PDMS- g -caPHEMA leads to a promoted endothelialization. Highlights • The bare PDMS surface shows a significant protein adsorption and platelet adhesion and activation. • PDMS surface coated with PHEMA brush exhibits excellent protein and platelet resistance and repels the endothelial cells. • Conjugation of the gelatin macromolecules onto the PHEMA-tethered PDMS surface leads to the improved endothelialization. Abstract Despite the distinct advantages of poly(dimethylsiloxane) (PDMS) for biomedical applications, because of its hydrophobic nature, suffers from non-specific protein adsorption and platelet adhesion and activation when used as a blood-contacting material. To confer hydrophilicity and biomolecules repelling characteristics, well-defined and high-density poly(2-hydroxyethyl methacrylate) (PHEMA) brushes are synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) on the PDMS substrate. First, PDMS surface is activated using an ultraviolet/ozone (UVO) wet treatment in water media to introduce hydroxy moieties without scarifying the surface property resulting a crack-free SiO 2 surface. Then, 3-(2-bromoisobutyramido)propyl(trimethoxy)silane (BrTMOS), the active ATRP initiator, is immobilized on the UVO-treated PDMS surface to prepare a thin layer of hydrophilic PHEMA brush on PDMS substrate exhibiting excellent protein and platelet resistance. PHEMA brushes supply a biomimetic feature by combining antifouling properties due to hydrophilic characteristic with bioactive properties resulted from the presence of a high density hydroxy groups, which are subsequently used for biomolecules conjugation. The results indicate that grafting of PHEMA chains on the PDMS surface enhances the surface wettability which leads to a decrease in non-specific protein adsorption and platelet adhesion compared to the bare PDMS substrate. The adhered platelets on the PHEMA-tethered PDMS substrate maintain their normal round morphology. Furthermore, the conjugated gelatin macromolecules onto the tethered PHEMA chains promote the adherence and growth of human umbilical vein endothelial cells via ligand-receptor interactions. [ABSTRACT FROM AUTHOR]

In this study, we report a new physicochemical surface on poly(dimethylsiloxane) (PDMS)-based silicone implants in an effort to minimize capsular contracture. Two different surface modification strategies, namely, microtexturing as a physical cue and multilayer coating as a chemical cue, were combined to achieve synergistic effects. The deposition of uniformly sized microparticles onto uncured PDMS surfaces and the subsequent removal after curing generated microtextured surfaces with concave hemisphere micropatterns. The size of the individual micropattern was controlled by the microparticle size. Micropatterns of three different sizes (37.16, 70.22, and 97.64 μm) smaller than 100 μm were produced for potential application to smooth and round-shaped breast implants. The PDMS surface was further chemically modified by layer-by-layer (LbL) deposition of poly- l -lysine and hyaluronic acid. Short-term in vitro experiments demonstrated that all the PDMS samples were cytocompatible. However, lower expression of TGF-β and α-SMA, the major profibrotic cytokine and myofibroblast marker, respectively, was observed in only multilayer-coated PDMS samples with larger size micropatterns (70.22 and 97.64 μm), thereby confirming the synergistic effects of physical and chemical cues. An in vivo study conducted for 8 weeks after implantation in rats also indicated that PDMS samples with larger size micropatterns and multilayer coating most effectively inhibited capsular contracture based on analyses of tissue inflammation, number of macrophage, fibroblast and myofibroblast, TGF-β expression, collagen density, and capsule thickness. Statement of Significance Although poly(dimethylsiloxane) (PDMS)-based silicone implants have been widely used for various applications including breast implants, they usually cause typical side effects called as capsular contracture. Prior studies have shown that microtexturing and surface coating could reduce capsular contracture. However, previous methods are limited in their scope for application, and it is difficult to obtain FDA approval because of the large and nonuniform size of the microtexture as well as the use of toxic chemical components. Herein, those issues could be addressed by creating a microtexture of size less than 100 m, with a narrow size distribution and using layer-by-layer deposition of a biocompatible polymer without using any toxic compounds. Furthermore, this is the first attempt to combine microtexture with multilayer coating to obtain synergetic effects in minimizing the capsular contracture. [ABSTRACT FROM AUTHOR]

Surface morphology plays a critical role in the functionality of PDMS. In this work, micro-cracks were prepared on PDMS surfaces by nanosecond pulsed laser irradiation under ambient conditions. To fully investigate the resulting morphologies and the underlying processing mechanism, confocal microscopy, scanning electron microscopy (SEM), μ-Raman, 2D Raman and atomic force microscope (AFM) methods were employed to observe the laser treated PDMS samples. The results reveal that the micro cracks are the dominated morphology along the laser scanning routes, with lengths ranging from 56 μm to 113 μm while the angles varied from 40° to 90°. To control crack propagation, the effect of laser fluence and scanning speed on the topography of the cracks was studied and a thermal-stress model was established to explain the propagation process. It is concluded that laser irradiation is an easy method of pattern PDMS surface with micro/nano dual scale structures. [ABSTRACT FROM AUTHOR]

Optically transparent flexible materials possessing high dielectric constant have tremendous applications in wide range applications such as flexible electronics devices, micro-electro-mechanical systems(MEMS),wearable sensors and biomedical devices. Out of all the polymers, PDMS(Polydimethylsiloxane) is very well known for its excellent properties and being utilized for biomedical devices and microfluidic applications. However, due to the poor electrical properties both electrical conductivity and dielectric constant, this material is not utilized as a sensing material for fabrication of wearable sensors or electronic devices. Though, some progress has been achieved to improve the conductivity of this material, for this purpose higher vol.% filler material is employed, that generate cracks and defects. Therefore, utilizing this material for the resistive based sensor fabrication is not that promising and also several applications such as touch screens, wearable electronics, touch sensors for keyboards, flexible switches and human-machine interfacing applications require capacitive-based sensors. In this work, we have developed a transparent flexible composite dielectric material by employing a very low vol.% chemically treated RGO as a filler in the PDMS matrix. The impacts of the uniform distribution of the RGO in the PDMS based composite’s flexibility, optical transparency and dielectric constant are investigated. The uniform distribution of the RGO in the PDMS matrix is obtained by the chemical treatment process prior to the fabrication of the composite, that helps to improve the flexibility of the composite material by improving the cross-linking bond between the RGO and PDMS matrix. Moreover, by controlling the uniform distribution of the RGO, it is possible to obtain 82% transparency with high dielectric constant(38) flexible composite material. We believe that this optical transparent and flexible composite can possibly be utilized for capacitive based wearable sensors, touch screens, touch sensors, flexible switches and flexible MEMS applications. [ABSTRACT FROM AUTHOR]

A plunger assisted solvent extraction (PASE) method for multi-channel silicone rubber trap samplers was developed and evaluated as an alternative to direct thermal desorption for the monitoring of polycyclic aromatic hydrocarbons (PAHs). The proposed extraction method was simple, fast (a total of 2 min for extraction), and used a small volume of solvent (a total of 2 mL from two sequential 1 mL extractions). The PASE method presented an advantage over thermal desorption in that samples could be re-analyzed, as only a portion of the extract was injected. Additionally, this approach is cost effective and can be applied in laboratories which do not have thermal desorption systems, hence allowing for the more widespread use of the polydimethylsiloxane samplers which can be employed as denuders in the monitoring of gas and particle partitioning of air pollutants. The method was validated over a wide concentration range (0.005–10 ng μL −1 ) and the limits of detection ranged from 13.6 ng m −3 for naphthalene to 227.1 ng m −3 for indeno[1,2,3-cd]pyrene. Overall extraction efficiencies of the target PAHs were good (from 76% for naphthalene to 99% for phenanthrene) with relative standard deviations below 6%. The PASE method was successfully applied to the analysis of domestic fire air emission samples taken at 10 and 20 min after ignition, using a sampling flow rate of 500 mL min −1 for 10 min in each case. The samples were found to contain primarily naphthalene (maximum concentration of 9.5 μg m −3 , 10 min after ignition), as well as fluorene, anthracene, phenanthrene, fluoranthene and pyrene. [ABSTRACT FROM AUTHOR]

Objective: Pelvic floor disorders, in particular pelvic organ prolapse (POP) and stress urinary incontinence (SUI), are common in women. There is a described higher risk to develop postoperative SUI also in preoperatively continent women: this happens because in 30% of women the relief of the urethral obstruction caused by prolapse, unmasks a pre-existing compromised urethral function and thus an "occult" or potential SUI. The aims of this study were to evaluate the role of Macroplastique® implant, TVT-O or surgery alone in the management of occult urinary stress incontinence during prolapse surgery in terms of success rate and adverse events.Study Design: We enrolled 47 consecutive patients scheduled to vaginal prolapse surgery who did not report symptoms of stress incontinence. We collected surgical data, success and complication rates. Moreover we compared all the data with retrospective ones regarding surgery plus concomitant TVT-O (39 pts) and surgery alone (41 pts).Results: At 12-months follow-up, we reported a success rate of 87,2% in the "macroplastique group", comparable to the "surgery plus TVT-O group", with a statistically significant difference in comparison to the "surgery alone" group. "Surgery + TVT-O" group reported a higher rate of major complications (p<0,01) in comparison to the other groups.Conclusions: Postoperative SUI prevention at the time of prolapse repair remains a challenging issue. In selected patients, Macroplastique may play an interesting role having a good success rate and a low complication rate and for these reasons it may be proposed as A concomitant procedure during POP surgery. [ABSTRACT FROM AUTHOR]

Formation of surfactant-laden aqueous drops by liquid flow through a capillary is studied and compared with two reference pure liquids, water and low viscosity poly(dimethylsiloxane). Attention is paid to two transitions: (i) between regimes with and without satellite droplet formation and (ii) from dripping to jetting. It is shown that transition from dripping to jetting occurs at critical Weber number We J  = 1.2 ± 0.1 based on dynamic surface tension on the flow timescale. Critical Weber number for transition to the regime without satellite droplets depends noticeably on the liquid surface tension and therefore cannot be used as a single parameter characterising this transition. Flow rate at transition decreases with decrease of surface tension for pure liquids and solutions of surfactants with critical micelle concentration, CMC > 10 mM. For solutions of surfactants with CMC < 1 mM transition to the regime without satellite droplets occurs at flow rates either larger or smaller than that of pure solvent depending on concentration. Anomalously high transition flow rates are related to surfactant redistribution during the time between the primary and secondary pinch-off. [ABSTRACT FROM AUTHOR]

In this work, a Multiwalled Carbon Nanotube/poly(alkylthiophene) (MWCNT/PT) composite is developed as the electrodes for dielectric elastomer actuators (DEAs) using the Langmuir-Schaefer (LS) method. These composites form stable monolayers at the air-water interface that can then be LS transferred onto a poly(dimethylsiloxane) (PDMS) elastomer membrane. The monolayer electrode remains conductive up to 100% uniaxial strain. We present a method to fabricate DEAs using the LS transferred electrodes. By using a mask during the transfer step, the electrodes can be patterned with better than 200 μm resolution on both sides of a 1.4 μm-thick pre-stretched PDMS membrane to produce an ultra-low voltage DEA. The DEA generates 4.0% linear strain at an actuation voltage of 100 V, an order of magnitude lower than the typical DEA operating voltage. [ABSTRACT FROM AUTHOR]

Conductive liquid silicone rubber-based composites were prepared through incorporation of fumed silica (FSiO 2 ) and polydimethylsiloxanes (PDMS) modified MWCNTs (P-MWCNTs), and their mechanical and electrical properties were investigated. It is shown that the introduction of P-MWCNTs with P-MWCNTs/FSiO 2 ratio of 0.25/30 (w/w) increases the cross-linking density and the thermal stability of the composites significantly. The improved mechanical performance, e.g., 60 % increase for Young's modulus and 47 % increase for tear strength, should be ascribed to the stronger interfacial interaction between P-MWCNTs and PDMS matrix and better dispersion of P-MWCNTs due to existence of PDMS on CNTs surface. Moreover, the better dispersion of P-MWCNTs also ensures much higher electrical conductivity than original carboxyl functionalized MWCNTs (COOH-MWCNTs) at relatively low loading, e.g., 10 −3  S m −1 versus 10 −8  S m −1 at MWCNTs/FSiO 2 ratio of 2.5/30, which could be attributed to the formation of CNTs network. [ABSTRACT FROM AUTHOR]

Soft thermoplastic polysiloxane-urea-elastomers (PSUs) were prepared for the application as a biomaterial to replace the human natural lens after cataract surgery. PSUs were synthesized from amino-terminated polydimethylsiloxanes (PDMS), 4,4′-Methylenebis(cyclohexylisocyanate) (H 12 MDI) and 1,3–Bis(3-aminopropyl)-1,1,3,3–tetramethyldisiloxane (APTMDS) by a two-step polyaddition route. Such a material has to be highly transparent and must exhibit a low Young’s Modulus and excellent dimensional stability. Polydimethylsiloxanes in the range of 3000–33,000 g·mol −1 were therefore prepared by ring-chain-equilibration of octamethylcyclotetrasiloxane (D 4 ) and APTMDS in order to study the influence of the soft segment molecular weight on the mechanical properties and the transparency of the PSU-elastomers. 2,4,6,8-Tetramethyl-2,4,6,8-tetraphenylcyclotetrasiloxane (D 4 Me,Ph ) was co-polymerized with D 4 in order to adjust the refractive index of the polydimethyl-methyl-phenyl-siloxane-copolymers to a value equivalent to a young human natural lens. Very elastic PSUs with Elongation at Break values higher than 700% were prepared. PSU-elastomers, synthesized from PDMS of molecular weights up to 18,000 g·mol −1 , showed transmittance values of over 90% within the visible spectrum range. The soft segment refractive index was increased through the incorporation of 14 mol % of methyl-phenyl-siloxane from 1.4011 to 1.4346 (37 °C). Young’s Moduli of PSU-elastomers were around 1 MPa and lower at PDMS molecular weights up to 15,000 g·mol −1 . 10-cycle hysteresis measurements were applied to evaluate the mechanical stability of the PSUs at repeated stress. Hysteresis values at 100% strain decreased from 32 to 2% (10th cycle) with increasing PDMS molecular weight. Furthermore, hysteresis at 5% strain was only detected in PSU-elastomers with low PDMS molecular weights. Finally, preliminary results of in vitro cytotoxicity tests on a PSU-elastomer showed no toxic effects on HaCaT-cells. [ABSTRACT FROM AUTHOR]

A novel simple and sensitive on-line flow injection (FI) fabric fiber sorbent extraction (FFSE) system adapted to flame atomic absorption spectrometry (FAAS) for automatic trace metal determination has been established. The FFSE platform is based on polyester fabric fibers coated with sol-gel poly-dimethylsiloxane (PDMS) packed into a microcolumn as sorbent packing material. The potentials of this new scheme were assessed for direct Pb(II) and Cd(II) determination in energy and soft drink samples. The on-line retention of target analytes on sol-gel coated fibers was carried out with sodium diethyl dithiocarbamate (DDTC), while elution was performed with methyl isobutyl ketone (MIBK). The effect of the main chemical and flow parameters on the sensitivity of the method was thoroughly studied. For a loading time of 90 s with a sampling frequency of 30 h − 1 , enhancement factors of 167 and 40 and detection limits (3 σ ) of 1.6 and 0.3 μg L − 1 were obtained for Pb(II) and Cd(II) determination, respectively. The trueness of the developed method was estimated by analyzing a certified reference material and spiked tap water. [ABSTRACT FROM AUTHOR]

Oxygen availability is a critical factor in regulating cell viability that ultimately contributes to the normal morphogenesis and functionality of human tissues. Among various cell culture platforms, construction of 3D multicellular spheroids based on microwell arrays has been extensively applied to reconstitute in vitro human tissue models due to its precise control of tissue culture conditions as well as simple fabrication processes. However, an adequate supply of oxygen into the spheroidal cellular aggregation still remains one of the main challenges to producing healthy in vitro spheroidal tissue models. Here, we present a novel design for controlling the oxygen distribution in concave microwell arrays. We show that oxygen permeability into the microwell is tightly regulated by varying the poly-dimethylsiloxane (PDMS) bottom thickness of the concave microwells. Moreover, we validate the enhanced performance of the engineered microwell arrays by culturing non-proliferated primary rat pancreatic islet spheroids on varying bottom thickness from 10 μm to 1050 μm. Morphological and functional analyses performed on the pancreatic islet spheroids grown for 14 days prove the long-term stability, enhanced viability, and increased hormone secretion under the sufficient oxygen delivery conditions. We expect our results could provide knowledge on oxygen distribution in 3-dimensional spheroidal cell structures and critical design concept for tissue engineering applications. Statement of Significance In this study, we present a noble design to control the oxygen distribution in concave microwell arrays for the formation of highly functional pancreatic islet spheroids by engineering the bottom of the microwells. Our new platform significantly enhanced oxygen permeability that turned out to improve cell viability and spheroidal functionality compared to the conventional thick-bottomed 3-D culture system. Therefore, we believe that this could be a promising medical biotechnology platform to further develop high-throughput tissue screening system as well as in vivo -mimicking customised 3-D tissue culture systems. [ABSTRACT FROM AUTHOR]

Traction forces generated at cellular focal adhesions (FAs) play an essential role in regulating various cellular functions. These forces (1–100 nN) can be measured by observing the local displacement of a flexible substrate upon which cells have been plated. Approaches employing this method include using microfabricated arrays of poly(dimethylsiloxane) (PDMS) micropillars that bend by cellular traction forces. A tool capable of applying a force to FAs independently, by actively moving the micropillars, should become a powerful tool to delineate the cellular mechanotransduction mechanisms. Here, we developed a patterned magnetic micropillar array PDMS substrate that can be used for the mechanical stimulation of cellular FAs and the measurement of associated traction forces. The diameter, length, and center-to-center spacing of the micropillars were 3, 9, and 9 µm, respectively. Iron particles were embedded into the micropillars, enabling the pillars to bend in response to an external magnetic field, which also controlled their location on the substrate. Applying a magnetic field of 0.3 T bent the pillars by ∼4 µm and allowed transfer of external forces to the actin cytoskeleton through FAs formed on the pillar top. Using this approach, we investigated the traction force changes in cultured aortic smooth muscle cells (SMCs) after local compressive stimuli to release cell pretension. The mechanical responses of SMCs were roughly classified into two types: almost a half of the cells showed a little decrease of traction force at each pillar following compressive stimulation, although cell area increased significantly; and the rest showed the opposite, with increased forces and a simultaneous decrease in area. The traction forces of SMCs fluctuated markedly during the local compression. The root mean square of traction forces significantly increased during the compression, and returned to the baseline level after its release. These results suggest that the fluctuation of forces may be caused by active reorganization of the actin cytoskeleton and/or its dynamic interaction with myosin molecules. Thus, our magnetic micropillar substrate would be useful in investigating the mechanotransduction mechanisms of cells. [ABSTRACT FROM AUTHOR]

In this paper, we report a selective-patterning method of active layers for the fabrication of solution-based amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs). Using simple stamping of a reusable poly(dimethylsiloxane) (PDMS) substrate onto a SiO X /Si substrate, the surface of SiOx/Si was easily changed to the hydrophobic state because the PDMS substrate contains a large amount of methyl ligands. By combining oxygen plasma treatments through a shadow mask, the active layer was self-defined through selective coating of the a-IGZO solution owing to the difference of the wetting properties. The electrical performance of the resulting TFTs was comparable with that of TFTs fabricated with the conventional method. Because the proposed method is very simple and the PDMS substrate is reusable compared to other selective-wetting methods that use self-aligned monolayers, it is expected to be applicable to the fabrication of low-cost and large-area electronic applications. [ABSTRACT FROM AUTHOR]

The aim of this work was to prepare and characterize the series of segmented polyurethane nanocomposites (PUNC) modified with poly(dimethylsiloxane) and based on montmorillonite (Mt) as a nano-filler. α , ω -Dihydroxy-poly(propylene oxide)- b -poly(dimethylsiloxane)- b -poly(propylene oxide) macrodiol was used as the soft segment component, while 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) were selected as the hard segment components. PUNC were synthesized with different ratio of hard/soft segments. PUNC were morphologically, structurally, thermally, mechanically and surface characterized by XRD, TEM, FTIR, AFM, TGA, DMTA, tensile test, XPS, contact angle, surface free energy (SFE) and water absorption measurements. Added Mt (1 wt%) was completely delaminated and well dispersed in the form of mixed exfoliated/intercalated layers in the polymer matrix, and that PUNC have more pronounced microphase separated morphology, higher thermal stability, superior mechanical features, enhanced surface properties, as well as outstanding hydrophobicity. Due to the improved features, developed polymers can be considered as candidates for materials with specific biomedical applications or as waterproof coatings. [ABSTRACT FROM AUTHOR]

A lab-on-a-CD immunoassay system was designed, fabricated, and tested. The actuator for the centrifugal platform consists of a flyball governor and a group of spring plungers. The microfluidic structures were fabricated using replica processes with poly-dimethylsiloxane (PDMS) as structural material. For better control, the valves in the microfluidic system were designed to be mechanical-pinch ones and actuated. The burst frequencies of the micro-valves can be tuned independently by adjusting the heights and pre-stresses of corresponding spring plungers. For the research work reported in this paper, four sequential valves and one inward pump were integrated on a centrifugal microfluidic system to develop an automated immunoassay system. Mouse IgG was used as a model analyte to test the feasibility of using the proposed device for immunoassay applications. Sample solution of goat anti-mouse IgG conjugated with magnetic nanoparticles was used for magnetic trapping mechanism to eliminate the blocking process. Rabbit anti-mouse IgG labeled with fluorescent molecules was used as the signal reporter. The entire microfluidic assay process, including beads trapping, immunoassay reaction, washing and pumping was completed in a centrifugal platform. The detection sensitivity may also be improved by using higher quality monoclonal antibodies. This new immunoassay platform offers some significant advantages over those reported in the field: simple fabrication, robust control, easy integration, and lower cost. The system may also be modified for detection of multiple targets. The technology has great potential for applications in complex fluid handling needed in biological, chemical and medical application in Lab-on-a-CD systems. [ABSTRACT FROM AUTHOR]

Necklace-shaped dimethylsiloxane (DMS) polymers bearing polyhedral oligomeric silsesquioxane (POSS) cages with “alternating modulated chain” arrangements were synthesized, by the polycondensation of a dimeric POSS precursor and dimethyl oligo-siloxane dichloride. Films of POSS-DMS polymers with “alternating modulated chain” arrangements were highly transparent. This observation is consistent with amorphous structures. Along with “constant chain” and “random chain” type polymers, three different chain arrangements of necklace-shaped polymers can now be produced. The physical properties of the three polymer types with constant POSS cage contents were compared. “Alternating modulated chain” type polymers had lower glass transition temperatures than the other two polymer types. This was attributed to the cooperative relaxation of long chain moieties that comprised half of the connecting chains. “Alternating modulated chain” type POSS-DMS polymers with average chain lengths of three to four exhibited heat resistances of over 470 °C in air. [ABSTRACT FROM AUTHOR]

Here, a simple and low-cost fabrication strategy to efficiently construct well-ordered micron and submicron gratings on polymeric substrates by oxygen plasma treatment is reported. The Polydimethylsiloxane (PDMS) substrate is prepared on the polyethylene (PET) by spin-coating method, then the curved PDMS-PET substrates are processed in oxygen plasma. After appropriate surface treatment time in plasma the curved substrates are flattened, and well-ordered wrinkling shape gratings are obtained, due to the mechanical buckling instability. It is also demonstrated that changing the curvature radius of PDMS-PET substrates and the time of plasma treatment, the period of the wrinkling patterns and the amplitude of grating also change accordingly. It is found the period of the wrinkling patterns increased with the radius of curvature; while the amplitude decreased with that. It also shows good optical performance in transmittance diffraction testing experiments. Thus the well-ordered grating approach may further develop portable and economical applications and offer a valuable method to fabricate other optical micro strain gauges devices. [ABSTRACT FROM AUTHOR]

This paper addresses the modification of poly(dimethylsiloxane), i.e. PDMS, using plasma surface treatment and a novel application of the membrane created. A set of model compounds were analysed to determine their permeation through PDMS, both with and without plasma treatment. It was found that plasma treatment reduced permeation for the majority of compounds but had little effect on some compounds, such as caffeine, with results indicating that polarity plays an important role in permeation, as is seen in human skin. Most importantly, a direct correlation was observed between plasma-modified permeation data and literature data through calculation of membrane permeability ( K p ) values suggesting plasma-modified silicone membrane (PMSM) could be considered as a suitable in vivo replacement to predict clinical skin permeation. [ABSTRACT FROM AUTHOR]

A novel injector for microchip electrophoresis (MCE) has been designed and evaluated that achieves very high repeatability of injection volume suitable for quantitative analysis. It eliminates the injection biases in electrokinetic injection and the dependence on pressure and sample properties in hydrodynamic injection. The microfluidic injector, made of poly(dimethylsiloxane) (PDMS), operates similarly to an HPLC injection valve. It contains a channel segment (chamber) with a well-defined volume that serves as an “injection loop”. Using on-chip microvalves, the chamber can be connected to the sample source during the “loading” step, and to the CE separation channel during the “injection” step. Once the valves are opened in the second state, electrophoretic potential is applied to separate the sample. For evaluation and demonstration purposes, the microinjector was connected to a 75 μm ID capillary and UV absorbance detector. For single compounds, a relative standard deviation (RSD) of peak area as low as 1.04% (n = 11) was obtained, and for compound mixtures, RSD as low as 0.40% (n = 4) was observed. Using the same microchip, the performance of this new injection technique was compared to hydrodynamic injection and found to have improved repeatability and less dependence on sample viscosity. Furthermore, a non-radioactive version of the positron-emission tomography (PET) imaging probe, FLT, was successfully separated from its known 3 structurally-similar byproducts with baseline resolution, demonstrating the potential for rapid, quantitative analysis of impurities to ensure the safety of batches of short-lived radiotracers. Both the separation efficiency and injection repeatability were found to be substantially higher when using the novel volumetric injection approach compared to electrokinetic injection (performed in the same chip). This novel microinjector provides a straightforward way to improve the performance of hydrodynamic injection and enables extremely repeatable sample volume injection in MCE. It could be used in any MCE application where volume repeatability is needed, including the quantitation of impurities in pharmaceutical or radiopharmaceutical samples. [ABSTRACT FROM AUTHOR]

Theophylline permeation experiments in poly(dimethylsiloxane) (PDMS) films modified by various amounts of a hydrophilic additive, polyethylene glycol (PEG) of molecular weight 3000 (present in the form of dispersed swellable spherical particles), were performed at 37 °C. The permeability coefficients derived from these data, increase systematically from a value of P = 2.0 × 10 –10 cm 2 /s for pure PDMS to P ∼ 15 × 10 –10 cm 2 /s for PDMS containing 20% w/w PEG, in line with the corresponding increase of the measured water uptake capacity of the films. The data were analyzed on the basis of the Maxwell model for binary composite materials consisting of a highly permeable swollen PEG phase dispersed in a continuous PDMS phase of a much lower permeability to theophylline. The requisite parameters for application of the model were derived from experimental information obtained from this work or from the literature. A good agreement between model and experimental results was found up to volume fractions of swollen PEG phase, well above those characterizing dilute dispersions. Effective P values were also derived from theophylline release kinetics from the corresponding matrices containing dispersed drug. Permeability coefficients from both types of experiments exhibit the same trends with increasing PEG content in the PDMS samples. Small differences in the absolute values of P are also discussed. [ABSTRACT FROM AUTHOR]

Styrenic butadiene block copolymer thermoplastic elastomer films (TPE) have been developed as an alternative to polydimethylsiloxanes (PDMS) for microfluidic applications. The integration of the TPE film to thermoplastic poly(methyl methacrylate) (PMMA), which is a critical step in microfluidic microfabrication process, has been performed by direct thermal bonding. It is found that surface treatment by plasma, in particular O 2 plasma, prior to bonding has significant effect in increasing hydrophilicity and bonding strength between the TPE film and PMMA. Moreover, the O 2 plasma treatment performed on surface of the TPE film is found to be much more effective in enhancing the bonding strength than on the PMMA. Using optimized bonding conditions, thermal bonding between the TPE film and PMMA chip has been achieved at low pressure and the microchannel integrity in the bonded joint is well retained with negligible clogging. Additionally, the effect of bonding temperature of 80 °C on mechanical properties of the TPE film has been studied through ageing test. The tensile strength and modulus of the TPE film do not change significantly even after 24 h ageing at 80 °C. [ABSTRACT FROM AUTHOR]

We propose a resistance-type strain sensor consists of hollow tubing graphene fibers (TGFs) with dimethylpolysiloxane (PDMS) coating for millimeters-scale strain/bending detection applications. The TGFs were synthesized via graphene films grown on Ni wire by chemical vapor deposition (CVD). The TGFs are fundamentally folded continuous few-layered graphene films without edges maintained cylindrical tube supported by PDMS coating. Sensing properties were studied comparing with a multi-wall carbon nanotube (MWCNT)/PDMS composites (CNTCs) and the mechanism were discussed. In terms of the gauge factor, the sensor made of TGF is estimated to be in the range of 34.3–48.9 against 8% tensile strain. For a feasibility study, we demonstrate the human finger monitoring by means of bending angle detection on a finger joint. [ABSTRACT FROM AUTHOR]

This paper reports on the hydrophobization of polyester fibrous nonwoven with poly(methylhydro-dimethyl)siloxane copolymers in order to produce water-repellent sorbents for oil spill cleanup. Polysiloxane copolymers were first synthesized and characterized prior to be used as hydrophobization agents. The produced hydrophobic sorbents were characterized by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX); infrared spectra (FTIR) and water-contact angle measurements (WCA). Nonwoven sorbents were evaluated for oil sorption in pure oil bath and in the presence of water ( W -test). A statistical experiment design was employed for materials testing and the development of data-driven models. The optimal hydrophobic nonwoven yielded maximal sorption capacities equal to 5.52 g/g and 10.03 g/g for dodecane and motor oil uptake, respectively. The mechanism of oil attachment on polymeric fibers was investigated by optical microscopy revealing a key role of inter-fiber voids for oil retention. Centrifugation tests demonstrated a high recycling ability of spent nonwoven sorbents. [ABSTRACT FROM AUTHOR]

Abstract In this work, we developed a simple method to fabricate a thickness-based continuous stiffness gradient for biological studies. It was made by glass slides, polydimethylsiloxane (PDMS) pre-polymer, spacer and clips only, without any sophisticated equipment. It is easy to fabricate in any general biological and pharmaceutical laboratories. The stiffness gradient was characterized in terms of apparent Young's modulus by atomic force microscopy (AFM) and the Young's modulus along the gradient was found to be 8.5–120 kPa, which is within the physiological relevant range. HeLa-C3 cells were cultured on the gradient to study their morphological behavior according to the substrate stiffness. Furthermore, the drug efficiency of etoposide, an anti-cancer drug, was studied along the substrate stiffness gradient. It was found that HeLa-C3 cells cultured on the soft region of the gradient (8.5–11 kPa) are more sensitive to etoposide. We believe the proposed device could promote cell investigations and drug screenings on a substrate with comparable stiffness to the native tissue. [ABSTRACT FROM AUTHOR]