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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.

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.

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.

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.

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.

In order to quantify the amount of drug molecules in drug delivery systems, analytical techniques such as high-performance liquid chromatography are used due to their accuracy and reliability. However, the instruments required for such techniques are expensive and not available in all laboratories. Therefore, in this study, we introduce a method that can be a relatively inexpensive and easy to perform drug analysis in almost any laboratory set-up. We have devised the &ldquo, average-weight-difference method&rdquo, within the limits of existing spectral analyses. By employing this method, we quantitatively analyzed the amount of isoniazid or doxorubicin molecules loaded onto &beta, glucan nanoparticles. This proved to be a relatively simple and reliable method and can be used to estimate the amount of nanoscale biomolecules before their analysis through expensive equipment in an environment where the instruments are not readily available.

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.

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.

The magnetic properties of ${\mathrm{Na}}_{5}{\mathrm{RbCu}}_{4}({\mathrm{AsO}}_{4}{)}_{4}{\mathrm{Cl}}_{2}$ are reported. The material has a layered structure comprised of square ${\mathrm{Cu}}_{4}{\mathrm{O}}_{4}$ tetramers. The Cu ions are divalent and the system behaves as a low-dimensional $S=1/2$ antiferromagnet. Spin exchange in ${\mathrm{Na}}_{5}{\mathrm{RbCu}}_{4}({\mathrm{AsO}}_{4}{)}_{4}{\mathrm{Cl}}_{2}$ appears to be quasi-two-dimensional and nonfrustrated. Measurements of the bulk magnetic susceptibility and heat capacity are consistent with low-dimensional magnetism. The compound has an interesting, low-entropy, magnetic transition at $T=17 \mathrm{K}.$