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Adhesion between flexible devices and skin surface facilitates portability of devices and reliable signal acquisition from human body, which is essential for medical therapy devices or monitoring systems. Here, we utilize a simple, cost-effective, and scalable layer-by-layer dip-coating method to fabricate a skin-adhesive multifunctional textile-based device, consisting of three parts: low-cost and easily available airlaid paper (AP) substrate, conductive MXene sensitive layer, and adhesive polydimethylsiloxane (PDMS). The adhesive layer of lightly cross-linked PDMS enables the device to form conformal contact with skin even during human joint bending. The smart textile device exhibits excellent electro-thermal and photo-thermal conversion performance with good cycling stability and tunability. Furthermore, the textile electronics show good electromagnetic interference (EMI) shielding properties due to the good electrical conductivity, as well as sensitive and stable pressure sensing properties for human motion detection. Consequently, this efficient strategy provides a possible way to design multifunctional and wearable electronic textiles for medical applications.

Recently, organic materials have emerged as next-generation thermoelectric (TE) materials because of their unique advantages including low cost, high mechanical flexibility, low or no toxicity, and...

High mechanical ductility and high mechanical strength are important for materials including polymers. Current methods to increase the ductility of polymers such as plasticization always cause a remarkable drop in the ultimate tensile strength. There is no report on the ductilization of polymers that can notably increase the elongation at break while not lowering the ultimate tensile strength. Here, we report the salt-induced ductilization of an intrinsically conducting polymer, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). Treating highly conductive PEDOT:PSS with a salt such as sodium perchlorate can enhance its elongation at break from 8.5 to 53.2%, whereas it hardly affects the tensile strength. Moreover, the resistance of the ductilized PEDOT:PSS films is insensitive to the tensile strain before fracture and slightly increases by only ~6% during the cyclic tensile testing with the strain up to 30%. These effects are ascribed to the decrease in the Coulomb attraction between PEDOT + and PSS − by the salt ions.

Stretchable, skin-interfaced, and wearable strain sensors have risen in recent years due to their wide-ranging potential applications in health-monitoring devices, human motion detection, and soft robots. High aspect ratio (AR) silver nanowires (AgNWs) have shown great potential in the flexible and stretchable strain sensors due to the high conductivity and flexibility of AgNW conductive networks. Hence, this work aims to fabricate highly stretchable, sensitive, and linear kirigami strain sensors with high AR AgNWs. The AgNW synthesis parameters and process windows have been identified by Taguchi’s design of experiment and analysis. Long AgNWs with a high AR of 1556 have been grown at optimized synthesis parameters using the one-pot modified polyol method. Kirigami sensors were fabricated via full encapsulation of AgNWs with Ecoflex silicon rubber. Kirigami-patterned strain sensors with long AgNWs show high stretchability, moderate sensitivity, excellent linearity (R2 = 0.99) up to 70% strain and can promptly detect finger movement without obvious hysteresis.

Harvesting energy from the environment to power the self-sustained systems has long been desired1,2. Ionic thermoelectric (i-TE) material with mobile ions as charge carriers has the advantage to generate large thermal voltages at low operating temperatures3-5. Recent works improved the thermopower substantially by modifying the polymer matrix of the i-TE hydrogels6-9. But the mobile ions have not been systematically studied in the context of i-TE hydrogels. This study highlights the role of ions in i-TE hydrogels employing a polyvinyl alcohol (PVA) polymer matrix and a number of ion providers, e.g. KOH, KNO3, KCl, KBr, NaI, KI, and CsI. The relationship between the intrinsic physical parameters of the ion and the thermoelectric performance is established, indicating electronegativity of the cation and the ability to influence the hydrogen bond by the anion are two crucial factors. Among these i-TE hydrogels, PVA/CsI hydrogel exhibits the largest ionic Seebeck coefficient, reaching 52.9 mV K-1, which is the greatest of all i-TE materials reported till date. In addition, PVA/NaI hydrogel exhibits excellent TE properties, with a record ZT value of 5.09 at room temperature. This flexible, inexpensive hydrogel that compatible with large-scale manufacturing shows great promise for low-grade thermal energy harvesting.

Monitoring surgical wounds post-operatively is necessary to prevent infection, dehiscence and other complications. However, the monitoring of deep surgical sites is typically limited to indirect observations or to costly radiological investigations that often fail to detect complications before they become severe. Bioelectronic sensors could provide accurate and continuous monitoring from within the body, but the form factors of existing devices are not amenable to integration with sensitive wound tissues and to wireless data transmission. Here we show that multifilament surgical sutures functionalized with a conductive polymer and incorporating pledgets with capacitive sensors operated via radiofrequency identification can be used to monitor physicochemical states of deep surgical sites. We show in live pigs that the sutures can monitor wound integrity, gastric leakage and tissue micromotions, and in rodents that the healing outcomes are equivalent to those of medical-grade sutures. Battery-free wirelessly operated bioelectronic sutures may facilitate post-surgical monitoring in a wide range of interventions. Multifilament surgical sutures functionalized with a conductive polymer and incorporating pledgets with capacitive sensors operated via radiofrequency identification can be used to monitor physicochemical states of deep surgical sites.

Electronic textile (e-textile) has emerged as a new generation of wearable electronics with these promising applications in healthcare and human movement detection. Herein, we report the gas-permeable and wearable e-textile strain sensors based on reduced graphene oxide/carbon nanotubes (rGO/CNTs) hybrids with unique structures grown on the low cost and eco-friendly non-woven fabric (NWF) by using a novel and facile nano-soldering method via ultrasonication. The gas-permeable rGO/CNTs e-textile strain sensors are highly sensitive and wearable, and the gauge factors of the rGO/CNTs hybrids sensors are 34.69 and 1.21 kPa−1 at 1 % tensile strain and 8.85 kPa pressure, respectively. Moreover, the gas-permeable and wearable rGO/CNTs e-textiles sensors also present good repeatability, super-hydrophobic performance, washability and durability at detecting stretching and compressing deformation, and it can be used for healthcare by monitoring the motions and blood pulse of human body.

The mechanical properties of formamidinium lead halide perovskites (FAPbX3, X = Br or I) grown by inverse temperature crystallization have been studied by nanoindentation. The measured Young's moduli (9.7 - 12.3 GPa) and hardnesses (0.36 - 0.45 GPa) indicate good mechanical flexibility and ductility. The effects of hydrogen bonding were evaluated by performing ab initio molecular dynamics on both formamidinium and methylammonium perovskites and calculating radial distribution functions. The structural and chemical factors influencing these properties are discussed by comparison with corresponding values in the literature for other hybrid perovskites, including double perovskites. Our results reveal that bonding in the inorganic framework and hydrogen bonding play important roles in determining elastic stiffness. The influence of the organic cation becomes more important for structures at the limit of their perovskite stability, indicated by high tolerance factors.

Thermal therapy is an effective physical treatment method for arthritis, stiff muscles, joint injuries, and injuries to the deep tissue of skin. Stretchable or even wearable electric heaters with uniform heating behavior are regarded as the next-generation electronic devices, which have been extensively studied for the personal thermal management and healthcare purpose. In this work, highly stretchable electrothermal heaters were developed by using composites of intrinsically conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS), elastomeric waterborne polyurethane (WPU) and reduced graphene oxide (rGO). rGO was mixed into the PEDOT:PSS/WPU blends to improve the temperature uniformity because rGO has high thermal conductivity while the polymers have very low thermal conductivity. The PEDOT:PSS/WPU/1 wt% rGO composite film exhibits an electrical conductivity of 18.2 S cm−1 and an elongation at break of 530%. The electrothermal performances of the polymer heaters were investigated with respect to the applied voltage, tensile strain, and the voltage on/off cycling process. The heater shows stable heating behavior under repetitive voltage on/off cycles, and the temperature remains almost unchanged under a tensile strain of up to 30%. The devices can be comfortably attached to the skin of humans, for example on the wrist, and they exhibit a uniform and stable heating profile even under mechanical disturbance. Due to their outstanding stretchability, biocompatibility, desirable electrical and thermal conductivities, the WPU/PEDOT:PSS/rGO composites can be used in wearable and long-term thermotherapy applications.

Hybrid organic–inorganic perovskite solar cells (PSCs) have attracted great interest owing to their low fabrication costs and high power conversion efficiency. Most studies have focused on the devices with methylammonium lead trihalide perovskites. Here, we explore a new perovskite with mixed organic cations and mixed halides, MA1−xFAxPbI3−yCly. MA1−xFAxPbI3−yCly films can be fabricated by annealing at a temperature of 80–110 °C. Planar heterojunction PSCs using this perovskite as the active material can exhibit a high power conversion efficiency (PCE) of up to 18.14% with short-circuit photocurrent density (Jsc) of 21.55 ± 0.55 mA cm−2, open-circuit voltage (Voc) of 1.100 ± 0.010 V, and fill factor (FF) of 0.75 ± 0.02. The PCE is much higher than those of the control devices with other commonly employed perovskites including MAPbI3, MAPbI3−yCly, MAPbI3−yBry, and MA1−xFAxPbI3. The superior performance is mainly attributed to the enhancement of Jsc, which is a result of long charge diffusion lengths due to the presence of mixed organic cations and mixed halides. In addition, there is no obvious hysteresis in the J–V curves along the forward and reverse scan directions. The formation of undesirable δ-phase perovskite that has a band gap of 2.8 eV is not observed in the MA1−xFAxPbI3−yCly films. These findings pave the way for the design of new hybrid perovskites with stronger light absorption over a wide range, lower charge recombination, and improved charge transport properties through compositional engineering.

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is the most successful conducting polymer in terms of practical application. It possesses many unique properties, such as good film forming ability by versatile fabrication techniques, superior optical transparency in visible light range, high electrical conductivity, intrinsically high work function and good physical and chemical stability in air. PEDOT:PSS has wide applications in energy conversion and storage devices. This review summarizes its applications in organic solar cells, dye-sensitized solar cells, supercapacitors, fuel cells, thermoelectric devices and stretchable devices. Approaches to enhance the material/device performances are highlighted.

The performance of perovskite solar cells (PSCs) including device efficiency and stability is mainly dependent on the perovskite film properties which are critically related to the organic cations used. Herein, we studied the role that the inorganic lithium (Li) cation played in perovskite thin films and its influence on crystal growth, film properties, and device performance. We found that within the threshold limit of a 1.0% molar ratio, the Li dopant had a positive effect on the film formation and properties. However, after replacing more MA+ with Li+, the device performance was degraded significantly with reduced short-circuit current density (Jsc) and fill factor (FF) values. With a doping ratio of 10 mol%, the film morphology, crystallinity, photophysical, and electronic properties totally changed due to the unstable nature of the Li doped, distorted 3-D perovskite structure. The Li doping mechanism was discussed, and it was thought to contain two different doping mechanisms. One is interstitial doping at the much lower doping ratio, and the other is substitutional doping for the MA cation at the higher doping ratio.

Various in-situ synthesis methods have been developed for the polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers, such as electro-polymerization (EP), oxidative chemical vapor deposition (OCVD) and vapor phase polymerization (VPP). Additional to these existing techniques, here a novel and facile method is introduced to fabricate highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films in-situ by solution means. The process contains sequential deposition of oxidants and monomers. V2O5 is introduced as the oxidant in this synthetic route. Excess reactants and by-products can be completely removed from the PEDOT film by MeOH-rinsing. The obtained PEDOT films possess good crystallinity and high doping level, with carrier concentration three orders of magnitude higher than the commercial product (PH1000, Heraeus GmbH). The electrical conductivity of the as-cast PEDOT film reaches up to 1420 S/cm. In addition, this method is fully compatible with large-scale printing techniques. A 15 cm × 12 cm PEDOT film is printed on polyethylene terephthalate (PET) substrate by bar coating. These PEDOT conducting films enable the realization of flexible touch sensors, which demonstrate superior flexibility and sensitivity. The low-cost and highly efficient synthetic method shows great potential for large-scale production of PEDOT films that have wide applications in electromagnetic shielding, antistatic coating, sensor, etc.

We explore a green method to grow metal alloy nanoparticles (NPs) on reduced graphene oxide stabilized with polyvinylpyrrolidone (PVP) in aqueous solution with sodium borohydride as a reducing agent for metal ions. PVP was used to stabilize nano-graphene sheets (NGs) in solution and prevent their aggregation. The synthetic experimental conditions were studied to control the size, shape and distribution of alloy nanoparticles anchored on the graphene sheets. AuPt nanoparticles on PVP-stabilized graphene (PVP-NGs-AuPt) show higher catalytic activity and stability than those on graphene without PVP (NGs-AuPt) toward the ethanol oxidation reaction (EOR) in alkaline media. PVP-NGs-AuPt can increase the EOR peak current density by more than 160%, ∼100% and 78% as compared with Pt on carbon, AuPt on carbon and NGs-AuPt, respectively. Moreover, the poisoning of PVP-NGs-AuPt during the EOR is less significant than that of NGs-AuPt, as revealed by analyzing the intermediates products, acetate and carbonate, by ion exchange chromatography. The high electrocatalytic activity of PVP-NGs-AuPt is attributed to the surface activation by OH − and the interaction between the AuPt NPs and graphene, which can improve the CO oxidation within the applied potential range.

Aberrant expression of long noncoding RNAs (lncRNAs) is associated with various human cancers. However, the role of lncRNAs in Bcr-Abl-mediated chronic myeloid leukemia (CML) is unknown. In this study, we performed a comprehensive analysis of lncRNAs in human CML cells using an lncRNA cDNA microarray and identified an lncRNA termed lncRNA-BGL3 that acted as a key regulator of Bcr-Abl-mediated cellular transformation. Notably, we observed that lncRNA-BGL3 was highly induced in response to disruption of Bcr-Abl expression or by inhibiting Bcr-Abl kinase activity in K562 cells and leukemic cells derived from CML patients. Ectopic expression of lncRNA-BGL3 sensitized leukemic cells to undergo apoptosis and inhibited Bcr-Abl-induced tumorigenesis. Furthermore, transgenic (TG) mice expressing lncRNA-BGL3 were generated. We found that TG expression of lncRNA-BGL3 alone in mice was sufficient to impair primary bone marrow transformation by Bcr-Abl. Interestingly, we identified that lncRNA-BGL3 was a target of miR-17, miR-93, miR-20a, miR-20b, miR-106a and miR-106b, microRNAs that repress mRNA of phosphatase and tensin homolog (PTEN). Further experiments demonstrated that lncRNA-BGL3 functioned as a competitive endogenous RNA for binding these microRNAs to cross-regulate PTEN expression. Additionally, our experiments have begun to address the mechanism of how lncRNA-BGL3 is regulated in the leukemic cells and showed that Bcr-Abl repressed lncRNA-BGL3 expression through c-Myc-dependent DNA methylation. Taken together, these results reveal that Bcr-Abl-mediated cellular transformation critically requires silence of tumor-suppressor lncRNA-BGL3 and suggest a potential strategy for the treatment of Bcr-Abl-positive leukemia.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful conducting polymer in terms of the practical application. It can be dispersed in water and some polar organic solvents, and high-quality PEDOT:PSS films can be readily prepared through solution processing. In addition, PEDOT:PSS is highly transparent in the visible range and has excellent thermal stability. Nevertheless, PEDOT:PSS has a problem of low conductivity. The as-prepared PEDOT:PSS films from its aqueous solution have a conductivity of lower than 1 S cm −1 , which severely impedes the application of PEDOT:PSS in various aspects. It has been discovered that the conductivity of as-prepared PEDOT:PSS from its aqueous solution can be significantly enhanced by adding organic compounds like high-boiling point polar organic solvents, ionic liquids and surfactants or through a post-treatment of PEDOT:PSS films with organic compounds, including high-boiling point polar solvents, salts, zwitterions, cosolvents, organic and inorganic acids. Conductivity of more than 3000 S cm −1 was recently observed on PEDOT:PSS films after treated with sulfuric acid. This conductivity is comparable to that of indium tin oxide (ITO), the conventional transparent electrode material of optoelectronic devices. In addition, PEDOT:PSS has high mechanical flexibility while ITO is a brittle material. Thus, PEDOT:PSS is very promising to be the next-generation transparent electrode material. This article reviews the methods to enhance the conductivity of PEDOT:PSS, the mechanisms for the conductivity enhancements and the application of the highly conductive PEDOT:PSS films in polymer light-emitting diodes and polymer solar cells.

This paper reports the doping of nanocrystalline TiO 2 with LiF by mechanical grinding and subsequent sintering and the application of LiF-doped TiO 2 as the photoanode of highly efficient dye-sensitized solar cells (DSCs). The fluoride ions can dope into the TiO 2 matrix as revealed by X-ray photoelectron spectroscopy (XPS). The LiF-doped TiO 2 samples are characterized by scanning electron microscopy (SEM), tunneling electron microscopy (TEM), X-ray diffraction (XRD), and UV–visible absorption spectroscopy. Doping of TiO 2 with a small amount of LiF can improve the photovoltaic performance of DSCs. At the optimal LiF loading of 0.53 wt% in TiO 2 , the power conversion efficiency (PCE) of DSCs is enhanced from 7.74% to 8.24% under simulated AM1.5 illumination. The effect of the LiF doping on the photovoltaic performance of DSCs is investigated by electrochemical impedance spectroscopy (EIS) and incident photon conversion efficiency (IPCE) measurements. The improvement in the photovoltaic efficiency is attributed to the facilitation of the electron transport through the TiO 2 electrode as a result of the increase in the anatase crystallinity induced by the LiF doping. The enhanced anatase crystallinity also causes a decrease in the charge recombination.

Graphene deposited with metal nanostructures can have important applications in various areas. This paper reports the in situ deposition of gold nanostructures with well-defined shapes, including triangular nanoplate and cuboid, on unfunctionalized reduced graphene oxide (rGO) by a two-step process. The first step is to coat a layer of HAuCl4 on an rGO film on glass, which is prepared by the reduction of a graphene oxide film with aluminum in an HCl solution. The second step is to reduce the dry HAuCl4 layer to metallic Au nanostructures with ethylene glycol vapor at 160 °C for 15 min, which gives rise to the deposition of Au nanostructures with well-defined shapes on rGO. No solvent or additives are added during the chemical reduction. The shape of the Au nanostructures depends on the Au loading. The majority of the Au nanostructures are triangular nanoplates, when the Au loading is low. The Au nanostructures with hexagonal nanoplate and pentahedron nanoplate shapes become remarkable at high Au loading. Moreover, the shape of the Au nanostructures can be changed to cuboid by introducing acids into the HAuCl4. The different shapes of the Au nanostructures deposited on rGO are interpreted in terms of the generation and diffusion rates of the Au atoms.

In this paper, we report a novel method to effectively fabricate the mesoporous TiO 2 films of dye-sensitized solar cells (DSCs) by formulating new TiO 2 pastes. Graphene oxide (GO) is added into TiO 2 nanoparticles pastes as an auxiliary binder. Thick mesoporous TiO 2 films free of crack can be prepared by only single printing. TiO 2 –GO pastes and films were characterized by dynamic mechanical analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and FTIR spectroscopy. TiO 2 pastes added with GO exhibit gel behavior. GO helps bind TiO 2 nanoparticles together through the interactions between functional groups on GO and the surface species of TiO 2 nanoparticles. The presence of 0.8 wt.% GO in the TiO 2 paste (GO weight percentage with respect to the weight of TiO 2 ) is sufficient to fabricate thick and crack-free TiO 2 films via single printing. These mesoporous TiO 2 films fabricated from the TiO 2 –GO pastes are investigated as the anode of DSCs. They can give rise to a power conversion efficiency (PCE) of 7.70% for DSCs under AM1.5G illumination, which is almost the same as that of control devices with the TiO 2 mesoporous electrode fabricated from the conventional TiO 2 paste without GO via four-fold printings.

This manuscript reports the modification of the interface between the mesoporous TiO 2 work electrode and electrolyte of dye-sensitized solar cells (DSCs) with oxide layers deposited by the thermal evaporation of metals and subsequent oxidation with UV ozone. Both Al 2 O 3 and MgO can be deposited on mesoporous TiO 2 by this method, and their thickness can be precisely controlled. A thin layer of Al 2 O 3 or MgO on the TiO 2 work electrode can improve the photovoltaic efficiency. The optimal thicknesses are 14.1 and 4.9 A for Al 2 O 3 and MgO, respectively. The oxide effect has been investigated by the electrochemical impedance spectroscopy, cyclic voltammetry and UV–Vis–NIR absorption spectroscopy. The improvement in the photovoltaic efficiency by an oxide layer is attributed to the upward shift of the conduction band of TiO 2 , the passivation of the TiO 2 surface, and the retardation of the charge recombination through the interface between TiO 2 and electrolyte.

Correction for ‘20.7% highly reproducible inverted planar perovskite solar cells with enhanced fill factor and eliminated hysteresis’ by Xixia Liu et al., Energy Environ. Sci., 2019, DOI: 10.1039/c9ee00872a.

Although intrinsically conductive polymers were discovered in 1970s, their application is quite limited mainly due to their poor processability and low conductivity. Most of conductive polymers are insoluble in any solvent and cannot melt. Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) has gained great attention and considered as the most successful conductive polymer, because it can be dispersed in water and some polar organic solvents. But it has a problem of low conductivity. The as-prepared PEDOT:PSS films from its aqueous solution usually has a conductivity of less than 1 S/cm. Here, I will present several novel methods to significantly enhance the conductivity of PEDOT:PSS. The conductivity can be enhanced to be more than 3000 S/cm. Thus, highly conductive PEDOT:PSS can be used as the transparent electrode of optoelectronic devices like solar cells because it can have high transparency in the visible range. In addition, they can exhibit high thermoelectric properties.

Composites of carbon nanotubes and graphene can give rise to superior function arising from the synergistic effects of the two components. Here, I will present some of our works in investigating the application of carbon nanotube/graphene composites in dye-sensitized solar cells and wearable sensors. The carbon nanotube/grpahene composites prepared by gel coating can effectively catalyze the regeneration of the redox species of dye-sensitized solar cells. They can give rise to a photovoltaic efficiency higher than that with carbon nanotubes, graphene or Pt as the counter electrode. Moreover, we prepare hybrid carbon nanotube/graphene on fibrics. They are sensitive to strain and can be used as washable wearable sensors.

Stretchable conductors can have important application in wearable electronics. We prepared stretchable conductors by blending poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS, a conductive polymer) and elastomeric waterborne polyurethane (WPU) and demonstrated the application of the blends for thermotherapy and electromagnetic interference (EMI) shielding. Wearable heaters were fabricated by using the stretchable PEDOT:PSS/WPU blends. rGO was mixed into the to improve the temperature uniformity because rGO has high thermal conductivity while the polymers have very low thermal conductivity. The heater shows stable heating behavior under repetitive voltage on/off cycles, and the temperature remains almost unchanged under a tensile strain of up to 30%. The devices can be comfortably attached to the skin of humans, for example on the wrist, and they exhibit a uniform and stable heating profile even under mechanical disturbance. In addition, the PEDOT:PSS/WPU blends can be investigated for EMI shielding. Flexible or even stretchable electromagnetic interference (EMI) shielding materials with high performance are needed for wearable electronic systems. The PEDOT:PSS/WPU blends can exhibit a high EMI shielding effectiveness (SE) of about 62 dB over the X-band frequency range at a film thickness of only 0.15 mm.

The shelf life of implantable materials has rarely been addressed. We determined whether osteoconductivity of titanium is stable over time. Rat bone marrow-derived osteoblasts were cultured on new titanium disks (immediately after acid-etching), 3-day-old (stored after acid-etching for 3 days in dark ambient conditions), 2-week-old, and 4-week-old disks. Protein adsorption capacity, and osteoblast migration, attachment, spread, proliferation and mineralization decreased substantially on old titanium surfaces in an age-dependent manner. When the 4-week-old implants were placed into rat femurs, the biomechanical strength of bone-titanium integration was less than half that for newly processed implants at the early healing stage. More than 90% of the new implant surface was covered by newly generated bone compared to 58% for 4-week-old implants. This time-dependent biological degradation was also found for machined and sandblasted titanium surfaces and was associated with progressive accumulation of hydrocarbon on titanium surfaces. The new surface could attract osteoblasts even under a protein-free condition, but its high bioactivity was abrogated by masking the surface with anions. These results uncover an aging-like time-dependent biological degradation of titanium surfaces from bioactive to bioinert. We also suggest possible underlying mechanisms for this biological degradation that provide new insights into how we could inadvertently lose, and conversely, maximize the osteoconductivity of titanium-based implant materials.

This study revealed that osteoblasts generate harder, stiffer, and more delamination-resistant mineralized tissue on titanium than on the tissue culture polystyrene, associated with modulated gene expression, uniform mineralization, well-crystallized interfacial calcium-phosphate layer, and intensive collagen deposition. Knowledge of this titanium-induced alteration of osteogenic potential leading to enhanced intrinsic biomechanical properties of mineralized tissue provides novel opportunities and implications for understanding and improving bone-titanium integration and engineering physiomechanically tolerant bone. Introduction: Bone-titanium integration is a biological phenomenon characterized by continuous generation and preservation of peri-implant bone and serves as endosseous anchors against endogenous and exogenous loading, of which mechanisms are poorly understood. This study determines the intrinsic biomechanical properties and interfacial strength of cultured mineralized tissue on titanium and characterizes the tissue structure as possible contributing factors in biomechanical modulation. Materials and Methods: Rat bone marrow-derived osteoblastic cells were cultured either on a tissue culture-grade polystyrene dish or titanium-coated polystyrene dish having comparable surface topography. Nano-indentation and nano-scratch tests were undertaken on mineralized tissues cultured for 28 days to evaluate its hardness, elastic modulus, and critical load (force required to delaminate tissue). Gene expression was analyzed using RT-PCR. The tissue structural properties were examined by scanning electron microscopy (SEM), collagen colorimetry and localization with Sirius red stain, mineral quantification, and localization with von Kossa stain and transmission electron microscopy (TEM). Results: Hardness and elastic modulus of mineralized tissue on titanium were three and two times greater, respectively, than those on the polystyrene. Three times greater force was required to delaminate the tissue on titanium than that on the polystyrene. SEM of the polystyrene culture displayed a porous structure consisting of fibrous and globular components, whereas the titanium tissue culture appeared to be uniformly solid. Cell proliferation was remarkably reduced on titanium. Microscopic observations revealed that the mineralized tissue on titanium was composed of uniform collagen-supported mineralization from the titanium interface to the outer surface, with intensive collagen deposition at tissue-titanium interface. In contrast, tissue on the polystyrene was characterized by collagen-deficient mineralization at the polystyrene interface and calcium-free collagenous matrix formation in the outer tissue area. Such characteristic microstructure of titanium-associated tissue was corresponded with upregulated gene expression of collagen I and III, osteopontin, and osteocalcin mRNA. Cross-sectional TEM revealed the apposition of a high-contrast and well-crystallized calcium phosphate layer at the titanium interface but not at the polystyrene interface. Conclusions: Culturing osteoblasts on titanium, compared with polystyrene, enhances the hardness, elastic modulus, and interfacial strength of mineralized tissue to a higher degree. Titanium per se possesses an ability to alter cellular phenotypes and tissue micro- and ultrastructure that result in enhanced intrinsic biomechanical properties of mineralized tissue.

Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs., There is a trade-off between increasing thickness of active layers in organic photovoltaic cells to be compatible with modern printing techniques and decreasing it to improve the device performance. Sun et al. report a nematic liquid crystalline molecular electron donor material used in thick layers.

The counter-anion doping states of poly(N-methylpyrrole) (PNMP) were studied by elemental analysis, mass analysis, cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and Vis-NIR spectra measurement. A part of counter anions and H+ cations left the PNMP film when it was immersed in distilled water, leading to the mass loss of the film, and the pH value drop of the water. The electro-chemical activity and doping level of the polymer in aqueous solution decreased with the increase of the solution pH value. The protonic acid doping form is proposed as one of the doping forms in PNMP, and deprotonation takes place in neutral and basic aqueous solutions.

A transparent biohybrid photoelectrochemical tandem cell is developed by employing optically-complementary variants of a photosynthetic protein in a stacked tandem architecture that utilizes a conductive polymer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), as a transparent counter electrode. The tandem design demonstrates the photocurrent enhancement by complementary absorption of two naturally-occurring red and green versions of a bacterial Reaction center/Light Harvesting protein (RC-LH1) that vary in the type of light harvesting carotenoid feeding the central reaction center module with excited state energy. The use of PEDOT:PSS electrode results in a 12-fold improvement in photocurrent compared to that achievable with Platinum.

The ferromagnetism in many carbon nanostructures is attributed to carbon dangling bonds or vacancies. This provides opportunities to develop new functional materials, such as molecular and polymeric ferromagnets and organic spintronic materials, without magnetic elements (for example, 3d and 4f metals). Here we report the observation of room temperature ferromagnetism in Teflon tape (polytetrafluoroethylene) subjected to simple mechanical stretching, cutting or heating. First-principles calculations indicate that the room temperature ferromagnetism originates from carbon dangling bonds and strong ferromagnetic coupling between them. Room temperature ferromagnetism has also been successfully realized in another polymer, polyethylene, through cutting and stretching. Our findings suggest that ferromagnetism due to networks of carbon dangling bonds can arise in polymers and carbon-based molecular materials.