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Recently, several methods have been used for cancer treatment. Among them, chemotherapy is generally used, but general anticancer drugs may affect normal cells and tissues, causing various side effects. To reduce the side effects and increase the efficacy of anticancer drugs, a folate-based liquid-metal drug nanodelivery system was used to target the folate receptor, which is highly expressed in cancer cells. A phospholipid-based surface coating was formed on the surface of liquid-metal nanoparticles to increase their stability, and doxorubicin was loaded as a drug delivery system. Folate on the lipid shell surface increased the efficiency of targeting cancer cells. The photothermal properties of liquid metal were confirmed by near-infrared (NIR) laser irradiation. After treating cancerous and normal cells with liquid-metal particles and NIR irradiation, the particles were specifically bound to cancer cells for drug uptake, confirming photothermal therapy as a drug delivery system that is expected to induce cancer cell death through comprehensive effects such as vascular embolization in addition to targeting cancer cells.

This paper presents a textile-based pH sensor with high flexibility fabricated by printing a polymer composite as a working electrode and Ag/AgCl/solid electrolyte as a reference electrode on a textile substrate. The textile working electrode is composed of polyaniline, carbon nanotubes, and agarose printed on the textile. A thermoplastic polyurethane overlayer hot-pressed on the textile substrates provides a smooth hydrophobic surface, enabling a more stable formation of the composite films with a reliable output signal. The textile reference electrode is fabricated by printing Ag/AgCl paste and solid electrolyte. The fully textile-based pH sensor, by integrating the textile working and reference electrodes, exhibits a good sensitivity of 45.9 mV/pH with high linearity. The textile pH sensor maintains excellent performance and repeatability with 93% retention even in a bent state and after 1000 bending cycles. Finally, it is demonstrated that the textile pH sensor can detect the pH change on a piece of porcine skin.

The hardness of poly (vinyl alcohol)-cryogels (PVA-CGs) was improved under three parameter conditions: 7.5 %-12.5 % PVA, 1-5 freezing-thawing cycles (FTCs), and the addition of 0 %-10 % glycerol as a cryoprotectant. This study investigated the effects of shear stress-induced destruction (SSID) on mechanical strength by inducing rapid erosion with a high frictional force. Tolerance to SSID (Tol-SSID) exhibited different sensitivities and trends depending on the above three fabrication parameters. The measured Tol-SSID exhibited consistent and inconsistent trends with tensile strength and swelling, respectively. Tol-SSID evaluation provides new insights into the practically meaningful mechanical strength of PVA-CGs against strong friction, which simulates extreme shear stress in a bioreactor. A PVA-CG with a PVA concentration of 10 % and in two FTCs resulted in Tol-SSID and tensile strength of 88.3 % and 0.59 kPa, respectively. Here, 5 % glycerol was added to maintain the bacterial respiration activity of immobilized nitrifiers of 0.097 mg-O

Due to the increasing energy consumption, smart technologies have been considered to automatically control energy loss. Smart windows, which can use external signals to modulate their transparency, can regulate solar energy by reflecting excess energy and retaining the required energy in a building without using additional energy to cool or heat the interiors of the building. Although many technologies have been developed for smart windows, they still need to be economically optimised. Here, we propose a facile method to synthesise magnetic microrods from magnetic nanoparticles by alignment using a magnetic field. To maximise the transparency difference in the ON and OFF states, we controlled the nanoparticle concentration in a dispersion liquid, magnetic field application time, and viscosity of the dispersant. Interestingly, the magnetic microrods remained stable when we mixed short-chain polymers (polyethylene glycol) with a liquid dispersant (isopropyl alcohol). Furthermore, the Fe2O3 microrods maintained their shape for more than a week, while the Fe3O4 microrods clustered after a day because they became permanent magnets. The anisotropic features of the magnetic rods were used as a light valve to control the transparency of the smart window.

Natural polymer materials have high biocompatibility and are not toxic because they can decompose into metabolites in the body; thus, they are widely used as medical polymer materials as well as porous support materials. As a biopolymer, alginate has a negative charge; in contrast, chitosan has a positive charge. Therefore, when the two substances are mixed, they form a relatively stable structure by ionic bonding. Beta-glucan is known to contribute to material stability and have high skin penetration, skin moisturizing and soothing effects, and burn and wound healing effects. In this study, antimicrobial activity was assessed by preparing alginate-chitosan hydrogel patches containing beta-glucan nanoemulsions. This could contribute to the development of wound dressings with antibacterial properties.

This paper describes a facile method for fabricating polyaniline (PANI) films with well-defined three-dimensional (3D) porous networks and improved electrochemical activity. The PANI hydrogel pastes with different compositions are directly cast into thin films by the doctor blade technique. After a dehydration step, the conductivity of the PANI drastically increases, while the porous structure with hierarchical macro- and meso-porosity is formed in the PANI film. The electrical conductivity tends to increase with the thickness of the porous PANI film until it fails to form a mechanically stable film not exhibiting cracking problems. We found that the amount of the initiator, the aniline monomer, and the crosslinker significantly affect not only the micro-morphology of PANI films, but also their electrical and electrochemical characteristics. Importantly, when the amounts of the crosslinker and the initiator increase, the polymer film forms with a dense internal morphology with smaller pores. Based on the engineered synthesis composition, we demonstrate a supercapacitor with porous PANI electrodes. Due to the hierarchical porous structure, large surface area and the improved conductivity, the resulting devices show excellent volumetric capacitances, which are comparable to or much higher than those previously reported.

Herein, we present the imbibition-induced, spontaneous, and selective wetting characteristics of gallium-based liquid metal alloys on a metallized surface with micro-scale topographical features. Gallium-based liquid metal alloys are fascinating materials that have enormous surface tension; therefore, they are difficult to pattern into films. The complete wetting of eutectic alloy of gallium and indium is realized on microstructured copper surfaces in the presence of HCl vapor, which removes the native oxide from the liquid metal alloy. This wetting is numerically explained based on the Wenzel’s model and imbibition process, revealing that the dimensions of the microstructures are critical for effective imbibition-driven wetting of the liquid metal. Further, we demonstrate that the spontaneous wetting of the liquid metal can be directed selectively along the microstructured region on the metallic surface to create patterns. This simple process enables the uniform coating and patterning of the liquid metal over large areas without an external force or complex processing. We demonstrate that the liquid metal-patterned substrates maintain electrical connection even in a stretched state and after repetitive stretching cycles.

The composite material, Ag/AgX/graphene (X=Br, Cl, I), is considered a promising photocatalyst for photocatalytic degradation of organic pollutants. Its photocatalytic activity is superior to that of the conventional TiO2 photocatalyst; the enhanced photocatalytic activity is attributed to its effective charge separation ability and wide visible light absorption. However, the Ag/AgX/graphene composite is often prepared in the powder form, limiting its wide-spread application. In addition, the simple fabrication of Ag/AgX/graphene composite films is highly challenging. In this study, a simple solution-based process based on meniscus-dragging deposition is demonstrated for the fabrication of Ag/AgI/rGO composite films. Uniform catalyst films with reasonable photocatalytic activities can be easily fabricated by using this microliter-scale solution process.

We report agarose-polymer-based composite microfibers with enhanced conductivity and fast humidity sensing owing to incorporation of conductive nanofillers. The microfibers are fabricated by extruding a hydrogel filament containing silver nanowires (AgNWs) and graphene oxide (GO, chemically reduced after extrusion) as 1D and 2D nanofillers, respectively. For the same concentration, GO enhances the mechanical properties of the microfibers more effectively than AgNWs. The microfiber with nanofillers has a higher Young's modulus than commercial nylon-6 and polyamide. Due to synergy between AgNWs and reduced GO (rGO), the microfiber with both fillers shows higher conductivity than those with only one filler. The flexible microfiber retains its conductivity well under repeated bending/unbending cycles. Since rGO ionizes water molecules, the conductivity of the microfiber increases with increasing environmental humidity. Humidity sensing ability of the composite microfiber, based on the humidity-dependent conductivity, is demonstrated. The microfiber with both nanofillers respond rapidly and reversibly to humidity changes because the AgNWs facilitate charge carrier transport and water adsorption/desorption. The humidity sensor based on the composite microfiber also reliably detects repeated short human breaths.

Organic solvents used for electrolytes of dye-sensitized solar cells (DSSCs) are generally not only toxic and explosive but also prone to leakage due to volatility and low surface tension. The representative dyes of DSSCs are ruthenium-complex molecules, which are expensive and require a complicated synthesis process. In this paper, the eco-friendly DSSCs were presented based on water-based electrolytes and a commercially available organic dye. The effect of aging time after the device fabrication and the electrolyte composition on the photovoltaic performance of the eco-friendly DSSCs were investigated. Plasma treatment of TiO2 was adopted to improve the dye adsorption as well as the wettability of the water-based electrolytes on TiO2. It turned out that the plasma treatment was an effective way of improving the photovoltaic performance of the eco-friendly DSSCs by increasing the efficiency by 3.4 times. For more eco-friendly DSSCs, the organic-synthetic dye was replaced by chlorophyll extracted from spinach. With the plasma treatment, the efficiency of the eco-friendly DSSCs based on water-electrolytes and chlorophyll was comparable to those of the previously reported chlorophyll-based DSSCs with non-aqueous electrolytes.

Elderly patients who underwent cataract surgery showed lower prevalence and cumulative incidence rates of hip and vertebral fragility fractures than those who did not. Therefore, cataract surgery in elderly patients may reduce the incidence of hip and vertebral fragility fractures.The purpose of this study was to compare the incidence rates of hip and vertebral fragility fractures between patients who underwent cataract surgery and those who did not, and to investigate the effect of cataract surgery on the incidence of fragility fracture in elderly population using nationwide claims data.A total of 558,147 participants from the National Health Insurance Service - Senior cohort were included. The participants were set into the hip fracture group (507,651) and vertebral fracture group (507,899) depending on the type of fracture.The number of hip fractures that occurred in the non-cataract surgery (NC) group was 36,971 (9.9%), while 8850 (6.6%) hip fractures occurred in the cataract surgery (C) group. The number of vertebral fractures that occurred in the NC group was 38,689 (10.3%), while 10,112 (7.6%) vertebral fractures occurred in the C group (all p .001). The hazard ratios of hip and vertebral fractures were 0.58 and 0.60 for the total population that had undergone cataract surgery (all p .001). The cumulative incidence rates of both fractures in the cataract surgery group were significantly lower than those in the non-cataract surgery group during 10 years (all p .0001).Elderly patients who underwent cataract surgery showed a lower prevalence of hip and vertebral fragility fractures than those who did not. In addition, the cumulative incidence rates of both fractures in the cataract surgery group were lower than those in the non-cataract surgery group. Therefore, cataract surgery in elderly patients may reduce the incidence of hip and vertebral fragility fractures.

The topical delivery of siRNA-based therapies has opened new avenues for the treatment of skin disorders. The use of siRNA as a therapeutic, however, is limited due to its rapid degradation and poor cellular uptake. Furthermore, the top layer of skin, the stratum corneum, is a major barrier to the delivery of topical agents. There is an unmet need for efficient topical formulations for delivering siRNA to the site of action. In this study, we used 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or lipofectamine to prepare a nanocarrier for delivering siRNA against glyceraldehyde 3-phosphate dehydrogenase (GAPDH); GAPDH expression was then evaluated at the cellular level. In addition, a dermal transport assay was designed and implemented to evaluate the penetration and delivery efficacy of siRNA in pig skin using lipid nanocarriers. The delivery of siRNA with the use of a lipid nanocarrier was significantly better than the delivery of siRNA without it. Thus, Our findings identify lipid nanocarriers as excellent candidates for the transdermal delivery of siRNA for gene silencing in the skin and thus for applications in related preclinical models.

β-Glucan, a polysaccharide biopolymer, is one of the constituents of cell walls of microorganisms, basidiomycetes, and plants. It has pathogen-associated molecular patterns, recognizing specific im...

This paper introduces composite microfibers that can distinguish liquid, normal, aliphatic alcohols with high selectivity. The composite microfibers are composed of a hydrophilic agarose polymer and carbon nanotube (CNT) fillers. The CNTs distributed in the CNT-agarose composite microfiber (CAF) enable the material to sensitively change its electrical conductivity upon exposure to alcohols, induced by a change in the volume of the polymer matrix. When a CAF is highly hydrated, its resistance distinctly changes depending on the molecular weight of the alcohol via competitive mass transfer of alcohol and water. As a result, highly hydrated CAFs can selectively distinguish normal, aliphatic alcohols ranging from methanol to 1-pentanol. A provisional mechanism for the alcohol-dependent change in resistance of hydrated CAFs is suggested based on the permeation of alcohols and the discharge of water and is supported by numerical calculations using a simple diffusion model. The effects of the CNT loading ratio and the as-prepared CAF diameter on the alcohol-dependent resistance change are investigated. Furthermore, the highly hydrated CAFs are used to determine the volume ratios of binary mixtures of methanol/ethanol and ethanol/water. Finally, we demonstrate that a CAF alcohol sensor can identify commercial liquors with different alcohol contents.

Eutectic gallium-indium alloy (EGaIn) liquid metal is highly conductive, moldable, and extremely deformable and has attracted significant attention for many applications, ranging from stretchable electronics to drug delivery. Even though EGaIn liquid metal is generally known to have low toxicity, the toxicity of the metal, rather than a salt form of Ga or In, has not been systematically studied yet. In this paper, we investigate the time-dependent concentration of the ions released from EGaIn liquid metal in an aqueous environment and their cytotoxicity to human cells. It is observed that only the Ga ion is dominantly released from EGaIn when no external agitation is applied, whereas the concentration of the In ion drastically increases with sonication. The cytotoxicity study reveals that all human cells tested are viable in the growth media with naturally released EGaIn ions, but the cytotoxicity becomes significant with sonication-induced EGaIn releasates. On the basis of the comparative study with other representative toxic elements, that is, Hg and Cd, it could be concluded that EGaIn is reasonably safe to use in an aqueous environment; however, it should be cautiously handled when any mechanical agitation is applied.

Gallium-based liquid metal (GaLM) alloys have been extensively used in applications ranging from electronics to drug delivery systems. To broaden the understanding and applications of GaLMs, this paper discusses the interfacial behavior of eutectic gallium-indium liquid metal (EGaIn) droplets in various solvents. No significant difference in contact angles of EGaIn is observed regardless of the solvent types. However, the presence or absence of a conical tip on EGaIn droplets after dispensing could indirectly support that the interfacial energy of EGaIn is relatively low in non-polar solvents. Furthermore, in the impact experiments, the EGaIn droplet bounces off in the polar solvents of water and dimethyl sulfoxide (DMSO), whereas it spreads and adheres to the substrate in the non-polar solvents of hexane and benzene. Based on the dimensionless We number, it can be stated that the different impact behavior depending on the solvent types is closely related to the interfacial energy of EGaIn in each solvent. Finally, the contact angles and shapes of EGaIn droplets in aqueous buffer solutions with different pH values (4, 7, and 10) are compared. In the pH 10 buffer solution, the EGaIn droplet forms a spherical shape without the conical tip, representing the high surface energy. This is associated with the dissolution of the “interfacial energy-reducing” surface layer on EGaIn, which is supported by the enhanced concentration of gallium ion released from EGaIn in the buffer solution.

For decades, scientists have been using two-dimensional cell culture platforms for high-throughput drug screening of anticancer drugs. Growing evidence indicates that the results of anti-cancer drug screening vary with the cell culture microenvironment, and this variation has been proposed as a reason for the high failure rate of clinical trials. Since the culture condition-dependent drug sensitivity of anti-cancer drugs may negatively impact the identification of clinically effective drug candidates, more reliable in vitro cancer platforms are urgently needed. In this review article, we provide an overview of how cell culture conditions can alter drug efficacy and highlight the importance of developing more reliable cancer drug testing platforms for use in the drug discovery process. The environmental factors that can alter drug delivery and efficacy are reviewed. Based on these observations of chemoresistant tumor physiology, we summarize the recent advances in the fabrication of in vitro cancer models and the model-dependent cytotoxicity of anti-cancer drugs, with a particular focus on engineered environmental factors in these platforms. It is believed that more physiologically relevant cancer models can revolutionize the drug discovery process.

Conductive biomaterials with a suitable biocompatibility have been utilized to fabricate in vitro platforms for differentiation of progenitor cell population as well as implantable tissue engineering scaffolds. This review evaluates biocompatibility of various conductive biomaterials and relevant fabrication techniques including coating, incorporation into composites, and functionalization with biological moieties. In addition, recent developments in tissue engineering applications using various conductive biomaterials are discussed in detail. Therefore, this overview could provide fundamental knowledge for engineering strategies in regulation of stem cell differentiation, maintenance of phenotypic characteristics, and design of functional implantable scaffolds for better regenerative medicines.

Fiber electrodes provide interesting opportunities for energy storage by providing both mechanical flexibility and the opportunity to impart multifunctionality to fabrics. We show here carbon nanotube (CNT)-embedded agarose gel composite fiber electrodes, with a diameter of ∼120 μm, consisting of 60 wt % CNTs that can serve as the basis for flexible and wearable fiber microsupercapacitors (mSCs). Via an extrusion process, CNT bundles are induced to align in an agarose filament matrix. Due to the shear alignment of the CNT bundles, the dehydrated filaments have an electrical conductivity as high as 8.3 S cm–1. The composite fiber electrodes are mechanically stable, enabling formation of twisted two-ply fiber mSCs integrated with a solid electrolyte. The fiber mSC shows a high capacitance (∼1.2 F cm–3), good rate retention (∼90%) at discharge current densities ranging from 5.1 to 38 mA cm–3, long cycle life under repeated charging/discharging (10% fade after 10 000 cycles) and good performance after at leas...

Generally, the fabrication of curved structures such as microlens arrays has been regarded as an expensive and complicated process. Here, we propose a facile method to form a microlens array with controlled lens curvature by combining residue-free nanoimprint lithography (NIL) with V-shaped molds and the successive thermal reflow procedure of the printed polymeric structures. The V-shaped molds used in this study enable the bottom substrate to be exposed after the NIL process when the initial thickness is controlled. Then, we use the thermal reflow to realize hemi-cylindrical curved lenses by applying heat. The polymers are self-pinned on the exposed substrate, which is strong enough to fix the boundary to not dewet or be flattened in the broad temperature range of the reflow process, which is essential for a large-area fabrication. Furthermore, we demonstrate the modulation of the focal lengths of the lenses by controlling the initial polymer thickness coated on a substrate.

The unique profile of upregulated glycosylation in metastatic cancer cells may form the basis for the development of new biomarkers for the targeting and diagnosis of specific cancers. This study introduces a pancreatic cancer cell-derived exosome detection technology, which is based on the specific binding of lectins to distinctive glycan profiles on the surface of exosomes. Lectins with a high and specific affinity for sialic acid or fucose were attached to bifunctional Janus nanoparticles (JNPs), which facilitated interactions with pancreatic cancer cell-derived exosomes in a microfluidic device. Here, we show that pancreatic cancer cell-derived exosomes from two cell lines and plasma samples collected from patients diagnosed with pancreatic cancer were successfully captured on the lectin-conjugated JNPs with affinities that were comparable to those of CA19-9, a conventional antibody. In addition, exosome detection using our platform could differentiate between metastatic and nonmetastatic pancreatic cancer cells. This study opens the possibility to achieve a new early diagnosis marker based on the glycan properties of pancreatic cancer cell-derived exosomes.

We have previously demonstrated a microfluidic elastomer, which changes apparent color and could have potential applications in smart windows. The practical use of such functional microfluidic systems requires rapid and uniform fluid displacement throughout the channel network with minimal amount of liquid supply. The goal of this simulation study is to design various microfluidic networks for similar applications including, but not limited to, the color-switching windows and compare the liquid displacement speed and efficiency of the designs. We numerically simulate and analyze the liquid displacement in the microfluidic networks with serpentine, parallel and lattice channel configurations, as well as their modified versions with wide or tapered distributor and collector channels. The data are analyzed on the basis of numerical criteria defined to evaluate the performance of the corresponding functional systems. We found that the lattice channel network geometry with the tapered distributors and collectors provides most rapid and uniform fluid displacement with minimum liquid waste. The simulation results could give an important guideline for efficient liquid supply/displacement in emerging functional systems with embedded microfluidic networks.

With the growing demand for measurements of organophosphate (OP) pesticide use in agriculture along with the potential threat of OP-based chemical warfare agents, there is a need for new devices or surfaces that can quickly degrade OPs into less toxic substances in a variety of environments. Using surface-initiated atom transfer radical polymerization and post-polymerization synthesis, we prepared a series of quaternary ammonium fluoride-based polymer brushes designed to absorb and degrade OPs. Specifically, a polymer brush was formed using 2-dimethylamino-ethyl methacrylate (DMAEMA) as monomer, which, following post-polymerization quaternization of the tertiary amine with alkylating agents and fluoride ion exchange, afforded the OP-reactive polymer surfaces. Poly(DMAEMA) brushes were grown to thicknesses of ~100 nm on silicon wafers and glass slides and characterized by ellipsometry, atomic force microscopy, and Raman spectroscopy. Quaternization and subsequent ion exchange of the brushes were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy, respectively. The interaction of the brushes with OPs was evaluated using the OP-based pesticide coumaphos, through the presence of the highly fluorescent degradation product chlorferon; analyzed qualitatively via fluorescence microscopy; and confirmed via nuclear magnetic resonance and mass spectrometry. We found that the fluoride form of the brush reliably degraded coumaphos deposited via controlled solution-based applications and aerosol applications (electrohydrodynamic jetting) and from microcontact printing of the dried solid directly onto the brush. No degradation was seen for coumaphos deposited on poly(DMAEMA) or the iodide form of the quaternized brush. Copyright © 2016 John Wiley & Sons, Ltd.

>> Recent years, supercapacitors have been attracting a growing attention as an efficient energy storage,due to their long-lifetime, device reliability, simple device structure and operation mechanism and, most importantly,high power density. Along with the increasing interest in flexible/stretchable electronics, the supercapacitors withcompatible mechanical properties have been also required. A eutectic gallium-indium (EGaIn) liquid metal couldbe a strong candidate as a soft electrode material of the supercapacitors because of its insulating surface oxidelayer for electric double layer formation. Here, we report the electrochemical study on the charging/reaction process at the interface of EGaIn liquid metal and electrolyte. Numerical fitting of the charging current curves provides the capacitance of EGaIn/insulating layer/electrolyte (~38 F/m 2 ). This value is two orders of magnitude higherthan a capacitance of a general metal electrode/electrolyte interface.Key words : Eutectic Gallium-indium liquid metal(갈륨-인듐 공융합금), Supercapacitor(수퍼커패시터), Oxide layer(산화막), Electrochemistry(전기화학), Electric double-layer(전기 이중층)

In many previous studies on humidity sensors based on composites embedded with conductive nanofillers, opposite (positive or negative) dependence of their electrical resistance on humidity has been reported. In this study, we systematically investigate the origin of opposite humidity-dependence of the resistance of agarose/carbon nanotube composites (A-CNTs) as a model composite material. Experimental results and impedance analysis reveal that the composites with more conductive fillers present positive dependence of resistance on humidity as an electronic pathway through the well-connected fillers is preferred for electrical conduction. In contrast, the composites with low filler content show negative dependence as the ionic pathway is more dominant for electrical conduction. The corresponding equivalent circuits for the nanofiller-embedded composites are suggested and the expected Nyquist plots depending on the filler content and humidity conditions are discussed. The process based on the impedance analysis potentially allows for non-destructive analysis of compositions and electrical property of composites as well as highly sensitive humidity detection.

Microbubbles and nanobubbles can be prepared using various shells, such as phospholipids, polymers, proteins, and surfactants. They are echogenic and can be used as contrast agents for ultrasonic and photoacoustic imaging. These bubbles can be engineered in various sizes as vehicles for gas and drug delivery applications with novel properties and flexible structures. Hypoxic areas in tumors develop owing to an imbalance of oxygen supply and demand. In tumors, hypoxic regions have shown more resistance to chemotherapy, radiotherapy, and photodynamic therapies. The efficacy of photodynamic therapy depends on the availability of oxygen in the tumor to generate reactive oxygen species. Micro/nanobubbles have been shown to reverse hypoxic conditions and increase tissue oxygen levels. This review summarizes the synthesis methods and shell compositions of micro/nanobubbles and methods deployed for oxygen delivery. In addition, the shortcomings and prospects of engineering micro/nanobubbles are discussed for their potential use in photodynamic therapy.

Microbubbles and nanobubbles (MNBs) can be prepared using various shells, such as phospholipids, polymers, proteins, and surfactants. MNBs contain gas cores due to which they are echogenic and can be used as contrast agents for ultrasonic and photoacoustic imaging. These bubbles can be engineered in various sizes as vehicles for gas and drug delivery applications with novel properties and flexible structures. Hypoxic areas in tumors develop owing to an imbalance of oxygen supply and demand. In tumors, hypoxic regions have shown more resistance to chemotherapy, radiotherapy, and photodynamic therapies. The efficacy of photodynamic therapy depends on the effective accumulation of photosensitizer drug in tumors and the availability of oxygen in the tumor to generate reactive oxygen species. MNBs have been shown to reverse hypoxic conditions, degradation of hypoxia inducible factor 1α protein, and increase tissue oxygen levels. This review summarizes the synthesis methods and shell compositions of micro/nanobubbles and methods deployed for oxygen delivery. Methods of functionalization of MNBs, their ability to deliver oxygen and drugs, incorporation of photosensitizers and potential application of photo-triggered theranostics, have also been discussed.

We present a facile microfluidic method for forming narrow chemical gradients in polymer brushes. Co-flow of an alkylating agent solution and a neat solvent in a microfluidic channel forms a diffusion-driven concentration gradient, and thus a gradient in reaction rate at the interface of the two flows, leading to a quaternization gradient in the underlying poly(2-(dimethylamino)ethyl methacrylate) polymer brush. The spatial distribution of the quaternized polymer brush is characterized by confocal Raman microscopy. The quaternization gradient length in the polymer brush can be varied with the injection flow rate and the distance from the co-flow junction. A chemical gradient in the polymer brush as narrow as 5 μm was created by controlling these parameters. The chemical gradient by laminar co-flow is compared with numerical calculations that include only one adjustable parameter: the reaction rate constant of the polymer brush quaternization. The calculated chemical gradient agrees with the experimental data, which validates the numerical procedures established in this study. Flow of multiple laminar streams of reactive agent solutions enables single-run fabrication of brush gradients with more than one chemical property. As one example, four laminar streams-neat solvent/benzyl bromide solution/propargyl bromide solution/neat solvent-generate multistep gradients of aromatic and alkyne groups. Because the alkyne functional group is a click-reaction available site, the alkyne gradient could allow small gradient formation with a wide variety of chemical properties in a polymer brush.

We report a general diffusion based method to form micrometer-scale lateral chemical gradients in polymer brushes via selective alkylation. A quaternized brush gradient is derived from a concentration gradient of alkylating agent formed by diffusion in permeable media around a microchannel carrying the alkylating agent. Polymer brushes containing both charge and aromatic gradients are formed using the alkylating agents, methyl iodide and benzyl bromide, respectively. The gradients are quantitatively characterized by confocal Raman spectroscopy and qualitatively by fluorescence microscopy. The length and gradient strength can be controlled by varying the diffusion time, concentrations, and solvents of the alkylating agent solutions. This microfluidic brush gradient generation method enables formation of 2-D chemical potential gradients with a diversity of shapes.

Graphene based electrical conductors are under consideration for numerous applications in energy storage, energy conversion devices, electronics and sensors. Here, we report a facile and versatile method for fabrication of graphene based composite microwires ranging from ∼20 to 250 μm in diameter via size reduction during dehydration of extruded larger diameter graphene oxide-loaded agarose hydrogel fibers. The graphene oxide is effectively reduced to graphene by chemical and thermal treatment. After dehydration and reduction, the resulting graphene composite microwires exhibit high electrical conductivities of up to 1.8 S m−1.

Hydrogel could serve as a matrix material of new classes of solar cells and photoreactors with embedded microfluidic networks. These devices mimic the structure and function of plant leaves, which are a natural soft matter based microfluidic system. These unusual microfluidic-hydrogel devices with fluid-penetrable medium operate on the basis of convective-diffusive mechanism, where the liquid is transported between the non-connected channels via molecular permeation through the hydrogel. We define three key designs of such hydrogel devices, having linear, T-shaped, and branched channels and report results of numerical simulation of the process of their infusion with solute carried by the incoming fluid. The computational procedure takes into account both pressure-driven convection and concentration gradient-driven diffusion in the permeable gel matrix. We define the criteria for evaluation of the fluid infusion rate, uniformity, solute loss by outflow and overall performance. The T-shaped channel network was identified as the most efficient one and was improved further by investigating the effect of the channel-end secondary branches. Our parallel experimental data on the pattern of solute infusions are in excellent agreement with the simulation. These network designs can be applied to a broad range of novel microfluidic materials and soft matter devices with distributed microchannel networks.

A soft-matter-based diode composed of hydrogel and liquid metal (eutectic gallium indium, EGaIn) is presented. The ability to control the thickness, and thus resistivity, of an oxide skin on the metal enables rectification. First, a simple model system with liquid-metal/electrolyte-solution/Pt interfaces is characterized. The electrically insulating oxide skin on the EGaIn electrode is reduced or oxidized further depending on the direction of the bias, thereby allowing unidirectional ionic current. The forward current of the diode increases as the conductivity of the electrolyte increases, whereas backward current depends on the pH of the medium in contact with the insulating oxide layer on the EGaIn electrode. As a result, the diode shows a higher rectification ratio (defined as the ratio of forward to backward current measured at the same absolute bias) with more conductive electrolyte at neutral pH. Replacement of the liquid electrolyte solution with a hydrogel improves the structural stability of the soft diode. The rectification performance also improves due to the increased ionic conductivity by the gel. Finally, a diode composed entirely of soft materials by replacing the platinum electrode with a second liquid-metal electrode is presented. Contacting each liquid metal with a polyelectrolyte gel featuring different pH values provided asymmetry in the device, which is necessary for rectification. A hydrogel layer infused with a strong basic polyelectrolyte removes the insulating oxide layer, allowing one interface with the EGaIn electrode to be conductive regardless of the direction of bias. Thus, the oxide layer at the other interface rectifies the current.

Effect of scattering particle size on light scattering efficiency in dye-sensitized solar cell has been investigated with a FTO/semitransparent nano-TiO 2 layer (main-layer)/scattering layer (overlayer) structure, where two different rutile TiO 2 particles of 0.3 μm (G1) and 0.5 μm (G2) were used for a scattering overlayer and 20-nm anatase particle for nano-TiO 2 main-layer. The conversion efficiency of 7.55% for the 7 μm-thick main-layer film is improved to 8.94% and 8.78% when G1 and G2 particulate overlayers are introduced, respectively, corresponding to 18.4% and 16.3% increments. While the conversion efficiency of the 14 μm-thick main-layer is slightly improved from 8.60% to 9.09% and 9.15% upon depositing G1 and G2 particulate overlayers, respectively. Significant improvement and strong size-dependence upon deposition of scattering overlayer on the relatively thinner TiO 2 main-layer film are associated with the quantity and wavelength of transmitted light and the difference in reflectivity of G1 and G2 scattering particles.

The effect of mask aperture size with respect to dye-adsorbed TiO 2 area on the response of photocurrent, voltage, fill factor and efficiency of dye-sensitized solar cell (DSSC) was recently studied by Gratzel's research group [S. Ito, Md. K. Nazeeruddin, P. Liska, P. Comte, R. Charvet, P. Pechy, M. Jirousek, A. Kay, S.M. Zakeeruddin, M. Gratzel, Prog. Photovolt. Res. Appl. 14 (2006) 589], where it was proposed that overall efficiency could be overestimated when measuring a DSSC without mask having adequate aperture size. In this report, beside the aperture size, we have studied effects of glass substrate thickness and geometry, thickness and layer structure of TiO 2 film on photovoltaic parameters. Photovoltaic parameters, mostly photocurrent density, were found to be significantly influenced by the glass substrate thickness and the TiO 2 layer structure. Data analysis suggests that photovoltaic characteristics before and after mask are dependent not only on measuring condition such as mask aperture size but also on substrate thickness and TiO 2 layer structure.

We report a new class of simple microfluidic strain sensors with high stretchability, transparency, sensitivity, and long-term stability with no considerable hysteresis and a fast response to various deformations by combining the merits of microfluidic techniques and ionic liquids. The high optical transparency of the strain sensors was achieved by introducing refractive-index matched ionic liquids into microfluidic networks or channels embedded in an elastomeric matrix. The microfluidic strain sensors offer the outstanding sensor performance under a variety of deformations induced by stretching, bending, pressing, and twisting of the microfluidic strain sensors. The principle of our microfluidic strain sensor is explained by a theoretical model based on the elastic channel deformation. In order to demonstrate its capability of practical usage, the simple-structured microfluidic strain sensors were performed onto a finger, wrist, and arm. The highly stretchable and transparent microfluidic strain sensors were successfully applied as potential platforms for distinctively monitoring a wide range of human body motions in real time. Our novel microfluidic strain sensors show great promise for making future stretchable electronic devices.

Materials which induce molecular motion without external input offer unique opportunities for spatial manipulation of molecules. Here, we present the use of polyacrylamide hydrogel films containing built-in chemical gradients (enthalpic gradients) to direct molecular transport. Using a cationic tertiary amine gradient, anionic molecules were directionally transported up to several millimeters. A 40-fold concentration of anionic molecules dosed in aerosol form on a substrate to a small region at the center of a radially symmetric cationic gradient was observed. The separation of mixtures of charged dye molecules was demonstrated using a boronic acid-to-cationic gradient where one molecule was attracted to the boronic acid end of the gradient, and the other to the cationic end of the gradient. Theoretical and computational analysis provides a quantitative description of such anisotropic molecular transport, and reveals that the gradient-imposed drift velocity is in the range of hundreds of nanometers per second, comparable to the transport velocities of biomolecular motors. This general concept of enthalpy gradient-directed molecular transport should enable the autonomous processing of a diversity of chemical species.