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Gel polymer electrolytes (GPEs) are emerging materials for Zn-air batteries (ZABs), since the GPE can act as a combined electrolyte and separator in the battery. GPE-KOH was fabricated through the...

Vanadium dioxide (VO2), a promising phase change material, exhibits insulator to metal transition at 68 °C, manifests a drastic change in multiple physical properties, such as electrical resistance, mechanical modulus, lattice parameters, etc. From technological perspective, the transition temperature can be reduced by precise strain engineering. Here a noncontact, all-optical, and highly energy efficient platform is demonstrated to study macroscopic dynamics related to the localized structural rearrangements at room temperature. A thin layer (≈25 nm) of polycrystalline VO2 deposited on a platinum coated silicon nitride microstring resonator shows a fast controlled mechanical resonance frequency response upon variations in optical power and wavelength. It is shown multiple stable frequencies of the resonator, designated as different equilibrium states, can be activated at different optical powers (≈200 µW) and wavelength, i.e., 450, 520, and 635 nm. The observed multiple resonance states of the microstring are explained because of the generation of stress due to the interplay between thermal expansion and the temperature-induced phase change of VO2. It is believed this change in frequency states under the controlled external optical excitation can have potential applications in ultrafast optical switching, intelligent temperature sensors, and neuromorphic devices operated at room temperature.

Polymorphism has emerged as an important design consideration in organic semiconductors (OSCs). Previously, in many OSCs, even small changes in molecular stacking can cause drastic changes to the o...

Despite recent developments in mechanosensors for biomedical applications, detection of broad ranges of mechanical signals with high sensitivity is still challenging. While crack based mechanosensors have shown huge potential in biomedical application because of their extraordinary sensitivity, there has been a structural limitation in that the high sensitivity has only been possible by in-plane strain with a specific directionality. Here, we demonstrate an advanced strategy to achieve enhanced sensitivity and signal linearity of the crack based pressure sensor by employing an anisotropic Poisson's ratio substrate (APS). The direction-specific pressure responsiveness can be assigned anisotropically by the sandwich structures of two honeycomb layers with distinctive moduli. Structural optimization of APS results in anisotropic Poisson's ratios of 0.67 and 0.11 in υzx and υzy, respectively, which allow a high sensitivity with 3.1 × 106 MPa−1 between 0 and 3 MPa with remarkable linearity by harnessing vertically applied stress (towards the z-axis) effectively to open lined cracks. As a demonstration, an array of crack based sensors is embedded in a jaw prosthesis for patients who have undergone mandible removal surgery. The embedded sensors evidence that they are capable of spatially resolved sensing in the events of mock biting at the physiological pressure ranges.

A model for the mechanics of a soft hyperelastic material reinforced with long fibers is presented in finite plane elastostatics. The strain energy potential of the composite is refined by the Mooney Rivlin model to accommodate the hyperelastic behaviors of the matrix material. Within the framework of the strain gradient theory, the kinematics of the fibers is formulated and subsequently integrated into the model of continuum deformation. A rigorous derivation of the Euler equation and the associated boundary conditions are presented by virtue of variational principles and a virtual work statement. In particular, the obtained model successfully predicts the ‘J-shaped’ stress-strain responses, deformation profiles and shear strain angles of the elastomer - polyester fiber composites subjected to uniaxial extension. The proposed model may also serve as an alternative of the Holzapfel model in the design and analysis of biomimetic composites with rapid strain-stiffening behaviors by providing direct estimations of the stress-strain responses of intended composites.

Natural tissues possess a so-called J-shaped strain-stiffening behavior, being soft and compliant at small strains followed by a rapid stiffening at higher strains to prevent tissue damage. In addi...

Compliant elastomer tubing with a fabric "jacket" has been essential in various applications as soft robotic actuators, such as in biomedical exomuscles and massage therapy implements. Here, our study shows that a similar design concept can be an effective strategy in realizing passive regulation in the tube's distension, as well as in preventing aneurysm-like asymmetric rupture of the tube. A custom hydraulic pressure testing rig was built to perform experiments. The jacketed tubes initially deform rapidly as pressure increases, but a self-regulation behavior suppresses the tube's continued distension by strain-stiffening of the "jacket". In addition, highly asymmetric distension, common to elastomeric tubes due to imperfection in fabrication, is prevented dramatically by the "jacket". A three-dimensional finite element model predicts the distension of all tested tubes quantitatively across the entire experimental pressure ranges and beyond. Incorporating custom-designed kirigami relief patterns in the "jackets" expands the potential of the elastomeric tubes.

Understanding the thermal properties of fluids at the nanoscale with high spatial, temporal, and thermal resolution are on great demand in the fields of MEMS, drug development, biomedical devices, and analytical systems. Microfluidic channel-integrated cantilevers are considered as an established benchtop sensor platform for physical and thermal characterization of materials at the picogram amount of analytes. This paper reports analysis of thermal characteristics of liquid analytes using photothermal heating effect of the microfluidic cantilever. Using real-time tracking of frequency shift of microfluidic resonator, the thermal properties of liquid samples can be estimated whilst the liquid analytes in the cantilever are locally heated by laser-induced irradiation. The heating results in the expansion of the liquid inside the channel which induces thermal stress on the walls of the channel. This thermal stress contributes to the rise of the resonance frequency of the microfluidic resonator and, therefore, the frequency shift is linearly dependent on the volumetric coefficient expansion of the liquid. A threefold improved sensitivity is observed when the second order flexural vibration mode is analyzed compared to that of the fundamental resonance. This approach, which combines photothermal heating and the dynamic mode of operation, can serve as a platform for the development of a portable, lab on a chip device for the use of real time detection of thermomechanical properties of fluids at low cost.

In rechargeable batteries, overpotential problems may occur especially when the battery is aging. An alarm system to prevent overpotential may be useful. Colloidal nanoparticles of Fe3O4@SiO2 can s...

Understanding the molecular mechanism of polymorphic transition is essential for controlling molecular packing for high-performance organic electronics. Polymorphic transition in molecular crystals...

An ex vivo heart perfusion device preserves the donor heart in a warm beating state during transfer between extraction and implantation surgeries. One of the current challenges includes the use of rigid and noncompliant plastic tubes, which causes injuries to the heart at the junction between the tissue and the tube. The compliant and rapidly strain-stiffening mechanical property that generates a "J-shaped" stress-strain behavior is necessary for producing the Windkessel effect, which ensures continuous flow of blood through the aorta. In this study, we mimic the J-shaped and anisotropic stress-strain behavior of human aorta in synthetic elastomers to replace the problematic noncompliant plastic tube. First, we assess the mechanical properties of human (n = 1) and porcine aorta (n = 14) to quantify the nonlinear and anisotropic behavior under uniaxial tensile stress from five different regions of the aorta. Second, fabric-reinforced elastomer composites were prepared by reinforcing silicone elastomers with embedded fabrics in a trilayer geometry. The knitted structures of the fabric provide strain-stiffening as well as anisotropic mechanical properties of the resulting composite in a deterministic manner. By optimizing the combination between different elastomers and fabrics, the resulting composites matched the J-shaped and anisotropic stress-strain behavior of natural human and porcine aorta. Finally, improved analytical constitutive models based on Gent's and Mooney-Rivlin's constitutive model (to describe the elastomer matrix) combined with Holzapfel-Gasser-Ogden's model (to represent the stiffer fabrics) were developed to describe the J-shaped behavior of the natural aortas and the fabric-reinforced composites. We anticipate that the suggested fabric-reinforced silicone elastomer composite design concept can be used to develop complex soft biomaterials, as well as in emerging engineering fields such as soft robotics and microfluidics, where the Windkessel effect can be useful in regulating the flow of fluids.

We demonstrate a simple, nonlithographic method for fabricating piezoresistive pressure sensors with a broad range of working pressures and low detection limit. Our wearable pressure sensor is fabr...

Ex situ heart perfusion (ESHP) is being investigated as a method for the continuous preservation of the myocardium in a semiphysiologic state for subsequent transplantation. Most methods of ESHP position the isolated heart in a hanging (H) state, representing a considerable departure from the in vivo anatomical positioning of the heart and may negatively affect the functional preservation of the heart. In the current study, cardiac functional and metabolic parameters were assessed in healthy pig hearts, perfused for 12 hours, in either an H, or supported (S) position, either in nonworking mode (NWM) or working mode (WM). The cardiac function was best preserved in the S position hearts in WM (median 11 hour cardiac index (CI)/1 hour CI%: working mode perfusion in supported position = 94.77% versus nonworking mode perfusion in supported position = 62.80%, working mode perfusion in H position = 36.18%, nonworking mode perfusion in H position = 9.75%; p0.001). Delivery of pyruvate bolus significantly improved the function in S groups, however, only partially reversed myocardial dysfunction in the H heart groups. The hearts perfused ex situ in a semianatomical S position and in physiologic WM had better functional preservation and recovery than the H hearts in non-S position. Optimizing the positional support for the ex situ-perfused hearts may improve myocardial preservation during ESHP.

Ex situ heart perfusion (ESHP) is being investigated as a method for the continuous preservation of the myocardium in a semiphysiologic state for subsequent transplantation. Most methods of ESHP position the isolated heart in a hanging (H) state, representing a considerable departure from the in vivo anatomical positioning of the heart and may negatively affect the functional preservation of the heart. In the current study, cardiac functional and metabolic parameters were assessed in healthy pig hearts, perfused for 12 hours, in either an H, or supported (S) position, either in nonworking mode (NWM) or working mode (WM). The cardiac function was best preserved in the S position hearts in WM (median 11 hour cardiac index (CI)/1 hour CI%: working mode perfusion in supported position = 94.77% versus nonworking mode perfusion in supported position = 62.80%, working mode perfusion in H position = 36.18%, nonworking mode perfusion in H position = 9.75%; p < 0.001). Delivery of pyruvate bolus significantly improved the function in S groups, however, only partially reversed myocardial dysfunction in the H heart groups. The hearts perfused ex situ in a semianatomical S position and in physiologic WM had better functional preservation and recovery than the H hearts in non-S position. Optimizing the positional support for the ex situ-perfused hearts may improve myocardial preservation during ESHP.

Zinc-air batteries (ZABs) have gained much attention from researchers in recent years, partly due to their high theoretical energy density as well as improved safety and the abundance of zinc relative to lithium in lithium-ion batteries (LIBs). Gel polymer electrolytes (GPEs) in ZABs can act as a separator and, therefore, can reduce the effect of dendrite formation at the zinc electrode. The temperature of many areas in Canada can be extremely low (less than -30oC) in the winter and many batteries do not work well at such low temperatures, mainly due to reduced rates for the electrochemical reactions in the battery. The objective of this work is to develop a GPE for ZABs using in-situ fabrication. The use of in-situ gelation can reduce the contact resistance between the GPE and the electrodes, thereby improving ion transport between the electrolyte and electrodes. The GPEs in this work are fabricated using poly(acrylic acid), crosslinked with KOH and a final immersion step in a mixture of additives. The additives are utilized to improve the performance of ZABs at low temperatures. As a redox mediator, KI can change the traditional oxygen evolution reaction in ZABs to a more thermodynamically favored reaction. ZnO is used to improve the cyclability of ZABs, whereas ethylene glycol is used to reduce the effect of hydrogel evolution at the zinc electrode.

Like silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS-P) crystals can undergo mechanically induced structural transitions to exhibit superelasticity and ferroelasticity. These properties arise from cooperative and correlated molecular displacements and rotations in response to mechanical stress. By utilizing a bending-induced ferroelastic transition of TIPS-P, flexible single-crystal electronic devices were obtained that can tolerate strains (ϵ) of more than 13 % while maintaining the charge carrier mobility of unstrained crystals (μ>0.7 μ0 ). Our work will pave the way for high-performance ultraflexible single-crystal organic electronics for sensors, memories, and robotic applications.

Polymorphism plays a major role in organic electronics, since even the slightest change in packing can modulate electronic properties. Controlling and accessing polymorphs of organic semiconductors...

Solid-state potassium ion selective electrode (K+ ISE) has been the most studied chemical sensors due to its practical importance in biomedical applications. One of the major obstacles that prevented widespread use of solid-state K+ ISE has been output potential drift problem. In this paper, we developed an electrochemical sensing unit in which working, counter, and reference electrodes are integrated in a single plane as all-solid-state form. In order to mitigate the output potential drift, a polyaniline intermediate layer and salt-saturated polyvinylebutyral top coating are introduced in the working and reference electrodes, respectively. Using cyclic voltammetry (CV), uniform layers of polyaniline are deposited on carbon electrode, as confirmed by scanning electron microscope observation. Potentiometry and electrochemical impedance spectroscopy measurement on our K+ ISE show high sensitivity (60.5 mV/decade), low concentration for the limit of detection ( $10^{-5.8}$ M), and large range of linear detection ( $10^{-5}-1$ M), and superior selectivity of K+ ISE against NH4+, Na+, Mg2+, Ca2+, and Fe3+. With its high potential to be miniaturized, we foresee that our solid-state K+ ISE will motivate the future applications in microdevices for clinical analysis, agricultural, and environmental applications.

The structure of polymer networks in hydrogels determines the properties. In this study, we investigated the structure of a charge-balanced polyampholyte, poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino) propyl] trimethylammonium chloride). From as-prepared samples, nanoscale globules were visualized in polyampholyte hydrogels for the first time. The impact of dialyses processes on polymer structures were also studied. In deionized water, salt ions are leached out, thus polymer chains undergo zipping process to form cellular structure with micrometer-thick polymer walls that allow mechanical toughness to the hydrogel. Samples dialyzed in 6 M potassium hydroxide solution did not show such cellular structure, as in the case of as-prepared samples.

Zinc–air batteries, which typically employ aqueous electrolytes, have attracted much attention owing to their high energy density, low cost, and environmental friendliness. While the zinc–air battery is a promising solution for energy grid applications, freezing of the electrolyte is an important problem for operation in cold climates. The freezing point of the electrolyte can be affected not only by chemical composition but also by micro/nanoscale confinement in porous electrodes or separators, and this is the focus of our work. First, we find osmotic virial coefficients by fitting experimental freezing point data for various electrolytes that are used in zinc–air batteries. Second, we show how additives that improve the performance of the batteries may also lower the freezing point of the electrolyte system. Third, we show how the nanoscale confinement inside zinc–air batteries further decreases the freezing point; a 10 nm diameter capillary pore can suppress the local freezing point of the electrolyte ...

The phase behavior of water in hydrogels has a broad impact on many health and energy applications. Our previous study showed that polyampholyte hydrogel has the potential to be used as an aqueous gel electrolyte in electrochemical storage devices at −30 °C due to enhanced low-temperature conductivity. In this study, we detail the impact polymer structure has on this enhanced conductivity, explaining this finding with a model charge-balanced polyampholyte, poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino)propyl]trimethylammonium chloride), a hydrogel whose polymer and water structures are probed by variable-temperature SAXS, WAXS, and solid-state NMR spectroscopy. SAXS results at room temperature indicate a networked globule structure in the charge-balanced polyampholyte hydrogels. The globular radius of gyration is ∼2.5 nm, whereas the globular size and its clustering structure are dependent on synthesis parameters. Variable-temperature SAXS data reveal a temperature-dependent structure evolution of...

To date, wearable sensors are increasingly finding their way into application of healthcare monitoring, body motion detection and so forth. A stretchable and wearable strain senor was fabricated on the basis of commercially available spandex/nylon fabric by the integration of conductive graphene network. Specifically, a simple graphene oxide dip-reduce method that enabled scalable fabrication pathway was employed. The good recovery of the graphene-coated fabric led to consistent resistance values despite the strain applied on the fabric and exhibited high gauge factor around 18.5 at 40.6% strain. Moreover, the graphene-coated fabric sensor could detect human motions such as finger bending with acceptable mechanical properties against un-coated fabrics, indicating that it has huge potential in wearable sensors applications.

Smart personal protective equipment (PPE) is the future of improved occupational health and safety, and nanotechnology facilitates the development of critical smart PPE components such as smart textiles, wearable/flexible electronics, and augmented reality among others. Smart PPE utilizes sensing and communication technology in a way that is non-intrusive to either improve workplace safety or enhance occupational capabilities. The development of such smart PPE requires a multidisciplinary approach. This paper investigates the current state of PPE technologies for firefighters, healthcare workers, police/military, and construction workers. The modern PPE needs are identified from both end user surveys as well as expert third-party studies. There are already some smart PPE solutions for the challenges identified. Recent advances in stretchable and textile-based electronics, enabled by nanotechnology, demonstrate almost all imaginable solutions to the unmet needs that PPE users and expert advisor groups have identified. However, integration into smart PPE requires attention to the unique harsh conditions of hazardous workplaces. This review aims to inspire researchers in the field of flexible and printed electronics to develop and improve future smart PPE.

The Quadruple Loop (QL) antenna was designed and investigated to deliver a robust body-worn antenna for bio-medical applications. The QL antenna is a very thin single-layer groundless structure which allows for the installation of neighboring electronics and sensors which need to be extremely close to the epidermis layer. The performance of the proposed antennas was investigated for three main standards: GSM-900, GSM-1800, and Bluetooth low energy (BLE). Radiation pattern measurements were conducted to compare their results with their simulation counterparts. Moreover, data communication tests showed that the acquired BER readings could qualify the BLE and GSM-900 antennas to work as part of 4-QAM wireless links. Besides these hands-on endeavors, an equivalent and more efficient mathematical model of biological tissues which make up the human arm was computed. The equivalent model was tested in software and has the practical potential to be realized in physical phantom making.

A flexible and self-healing supercapacitor with high energy density in low temperature operation was fabricated using a combination of biochar-based composite electrodes and a polyampholyte hydrogel electrolyte. Polyampholytes, a novel class of tough hydrogel, provide self-healing ability and mechanical flexibility, as well as low temperature operation for the aqueous electrolyte. Biochar is a carbon material produced from the low-temperature pyrolysis of biological wastes; the incorporation of reduced graphene oxide conferred mechanical integrity and electrical conductivity and hence the electrodes are called biochar-reduced-graphene-oxide (BC-RGO) electrodes. The fabricated supercapacitor showed high energy density of 30 Wh/kg with ~90% capacitance retention after 5000 charge–discharge cycles at room temperature at a power density of 50 W/kg. At −30 °C, the supercapacitor exhibited an energy density of 10.5 Wh/kg at a power density of 500 W/kg. The mechanism of the low-temperature performance excellence is likely to be associated with the concept of non-freezable water near the hydrophilic polymer chains, which can motivate future researches on the phase behaviour of water near polyampholyte chains. We conclude that the combination of the BC-RGO electrode and the polyampholyte hydrogel electrolyte is promising for supercapacitors for flexible electronics and for low temperature environments.

Bijels formed by the phase separation of polymer blends are described. After introducing applications of polymer nanocomposites formed from bijels, the fundamental thermodynamic and dynamic properties are reviewed. Because they underpin the formation of bijels and thin-film stability, the principles of spinodal decomposition, wetting and dewetting are described. These principles are applied to understand bijel formation, phase evolution and dewetting in poly(methyl methacrylate)/poly(styrene-ran-acrylonitrile) blends containing poly(methyl methacrylate)-grafted silica nanoparticles. The parameters that determine whether nanoparticles preferentially locate at the interface are described. Advances in numerical simulations help interpret experimental observations and guide future studies aimed at developing new functional bijel structures, with applications ranging from three-dimensional printing to membrane-based separations.

Tuning mechanical frequency of MEMS and MOEMS devices by integrating the conventional silicon-based devices with functional oxides has become very important recently for mechanical signal processing and ultrasensitive detection. Most of these devices have unidirectional frequency change with external stimuli. Here we show by exploiting the metal insulator transition (MIT) of phase change material (VO 2 ) bidirectional spatial frequency tuning (in acoustic range) is possible by the application of optothermal excitation. By fabricating VO 2 microstrings $(200\ \mu\mathrm{m}(\mathrm{L})\times 5\ \mu\mathrm{m}(\mathrm{w})\times 260(\mathrm{t})\ \mathrm{nm})$ we demonstrate that bidirectional resonance frequency (f r ) tuning is possible from −2 to +2% depending on the laser power. We further demonstrate that the change in resonance frequency in both the direction (positive or negative) can be also possible along the length of the microstring depending on the laser power.

Vanadium dioxide (VO2), because of its unique metal–insulator phase transion around room temperature, has enormous potential for applications in thermochromic, electrochromic, microbolometery, and non-volatile switches. However, obtaining phase-pure VO2 has been challenging due to its narrow window of thermodynamic stability. Pulsed laser deposition (PLD) is considered to be one of the most promising technique to deposit phase-pure VO2 thin films. While optimizing PLD processing parameters, (such as oxygen pressure (PO2), substrate temperature (Ts), laser energy (EL), target-substrate distance (dT-S), and laser repetition rate (RR)) is crucial, and their effects have been reported, the effect of gas flow rate (QO2) has been largely neglected. Since the QO2 and PO2 of the PLD system are intertwined at the outset, most reports are focused only on either QO2 or PO2. We report on the effect of gas flow rate under constant PO2, on the quality of the VO2 thin films. Controlling flow rate affected the resistivity contrast between the metallic and insulator phases, the temperature ranges of the transition, and the width of hysteresis. We anticipate that this study will help set the standard for obtaining high quality VO2 thin films.

To increase the cyclability of rechargeable zinc-air batteries (ZABs) using gel polymer electrolytes (GPEs), battery design and structure need to be optimized. Two different configurations for a tri-electrode battery have been developed in this work; i.e., a planar cell and a sandwich cell. Discharge-recharge cycling tests at 5 mA cm–2 show that the sandwich cell is more suitable for ZABs than the planar cell. Various additives for the GPEs, such as cross linking agents and ZnO, have also been evaluated using the tri-electrode design. Cross linking density affects the physical state of GPEs, which in turn affects the oxygen evolution reaction as there is an adverse effect of excessive GPE/Ni foam electrode contact area because oxygen bubbles may be trapped in the GPE. The addition of ZnO to the oxygen reduction reaction side of the battery enhances the cycling performance of ZABs; i.e., the battery can withstand at least 100 cycles at 5 mA cm–2 with an efficiency of 62% during the first cycle.

Opportunities for developing end-of-life sensors for fire resistant fabrics are explored using reduced graphene oxide coatings on textiles. Fire resistant fabrics are known to experience significant losses in performance over time. Large reductions in mechanical properties have also been recorded when these fabrics were subjected to accelerated aging conditions simulating the use in service. In addition, the fabric loss in performance may exceed the safety requirement threshold before any sign of damage is visible to the naked eye. Electrically conductive coatings and tracks were prepared on an m-aramid woven fabric using graphene oxide that was further reduced. The preparation technique allowed wrapping the individual aramid fibers with rGO sheets. No significant change in sheet resistance was recorded after up to 120h of immersion of the rGO-coated fabric specimens in water. An increase in resistance after 10 accelerated washing cycles was measured on the rGO-coated specimens prepared with 5 coating cycles while no significant effect was detected for specimens prepared with 10 and 15 coating cycles. Under abrasion exposure, the electrical resistance of rGO tracks increased gradually until 150 cycles, after which the conductivity dropped abruptly. These results show the potential of reduced graphene oxide applied as a coating on m-aramid fabrics to prepare end-of-life sensors for fire resistant fabrics.

Polyampholyte hydrogels (PAHs) constitute a class of physical gels with cross-linking originating from inter- and intrachain ionic cross-linking between countercharged functional groups. In our previous report, we have shown that PAH has the potential to be a gel electrolyte in electrochemical energy storage devices. In this work, we further our understanding of charge-balanced PAH as a host material for gel electrolytes by studying the effect of dialysis on the mechanical properties and ionic conductivities of PAHs, whereas these properties are compared with those of poly(vinyl alcohol) (PVA)-based gel electrolytes. Here, various electrolyte solutions were investigated as dialyzing agents. The ionic species in the electrolytes form ion pairs with countercharged functional groups in PAH, whereas such interactions govern the ionic conductivity and mechanical strength of PAH in various electrolytes. For anions, the trend in ionic interactions follows the Hofmeister series in an exact manner, whereas some anomaly is observed among cations. We anticipate that our study provides a design criterion for fabricating gel electrolytes. In a broader context, this work can shed light on understanding the behavior of PAHs in various operational environments, such as under physiological conditions and in antifouling coatings for biomedical and maritime applications, respectively.

A Cu2O coated Cu mesh with micro-scale surface structure was produced by a controlled UV-ozone treatment. The modified Cu mesh exhibited superhydrophilicity and underwater superoleophobicity. To achieve switchable wettability, the mesh's superhydrophilicity was converted to superhydrophobicity by application of a self-assembled monolayer (SAM) with stearic acid (SA), which can be repeatedly reversed to its original state (superhydrophilicity and underwater superoleophobicity) by UV treatment that causes SA decomposition. Gravity-driven kerosene/water separation was demonstrated with the separation efficiency remaining over 95% after 20 cycles for both “water-removal” and “oil-removal” separation modes.

Flexible electronics incorporate all the functional attributes of conventional rigid electronics in formats that have been altered to survive mechanical deformations. Understanding the evolution of device performance during bending, stretching, or other mechanical cycling is, therefore, fundamental to research efforts in this area. Here, we review the various classes of flexible electronic devices (including power sources, sensors, circuits and individual components) and describe the basic principles of device mechanics. We then review techniques to characterize the deformation tolerance and durability of these flexible devices, and we catalogue and geometric designs that are intended to optimize electronic systems for maximum flexibility.

Biochar, produced through pyrolysis of biomass under low or no oxygen conditions, has found a wide range of applications from soil fertility improvement to removal of contaminants. Initial interest in biochar is to use it as a means to capture carbon dioxide from the atmosphere; however, recent developments are seeing biochar being applied in engineering, and health care and life sciences, some of those applications have large potentials for rapid commercialization. We expect a paradigm shift towards the development of the next generation of biochar with applications in a range of new fields.

Uniform ZnO nanowires (NWs) were grown on cellulose filter paper via a modified one-step hydrothermal method. The ZnO coated filter paper exhibited superhydrophilicity and underwater superoleophobicity due to the surface roughness of the coated ZnO NWs. The coated cellulose filters demonstrated exceptional results at oil/water separation with high separation efficiency and experimentally proven recyclability for several oil/water mixtures. The outstanding separation performance and scalable growth method highlight potential for practical applications, such as wastewater treatment and polluted water purification.