Stretchable electronics, which can retain their functions under stretching, have attracted great interest in recent decades. Elastic substrates, which bear the applied strain and regulate the strain ...distribution in circuits, are indispensable components in stretchable electronics. Moreover, the self‐healing property of the substrate is a premise to endow stretchable electronics with the same characteristics, so the device may recover from failure resulting from large and frequent deformations. Therefore, the properties of the elastic substrate are crucial to the overall performance of stretchable devices. Poly(dimethylsiloxane) (PDMS) is widely used as the substrate material for stretchable electronics, not only because of its advantages, which include stable chemical properties, good thermal stability, transparency, and biological compatibility, but also because of its capability of attaining designer functionalities via surface modification and bulk property tailoring. Herein, the strategies for fabricating stretchable electronics on PDMS substrates are summarized, and the influence of the physical and chemical properties of PDMS, including surface chemical status, physical modulus, geometric structures, and self‐healing properties, on the performance of stretchable electronics is discussed. Finally, the challenges and future opportunities of stretchable electronics based on PDMS substrates are considered.
Elastic substrates, especially poly(dimethylsiloxane) (PDMS) substrates, are indispensable components for emerging stretchable electronics. Detailed design concepts and fabrication strategies for structured, patterned, and self‐healing PDMS substrates, and their contributions in enhancing the mechanical performance of stretchable electronics are discussed. Future perspectives and challenges in the development of stretchable and self‐healing PDMS substrates are highlighted.
The rapid development of integrated electronics and the boom in miniaturized and portable devices have increased the demand for miniaturized and on‐chip energy storage units. Currently thin‐film ...batteries or microsized batteries are commercially available for miniaturized devices. However, they still suffer from several limitations, such as short lifetime, low power density, and complex architecture, which limit their integration. Supercapacitors can surmount all these limitations. Particularly for micro‐supercapacitors with planar architectures, due to their unique design of the in‐plane electrode finger arrays, they possess the merits of easy fabrication and integration into on‐chip miniaturized electronics. Here, the focus is on the different strategies to design electrode finger arrays and the material engineering of in‐plane micro‐supercapacitors. It is expected that the advances in micro‐supercapacitors with in‐plane architectures will offer new opportunities for the miniaturization and integration of energy‐storage units for portable devices and on‐chip electronics.
In‐plane micro‐supercapacitors possess the merits of easy fabrication and integration into on‐chip electronics, and offer new opportunities for the miniaturization and integration of energy‐storage units for portable devices. Strategies to fabricate electrode finger arrays and the material engineering of in‐plane micro‐supercapacitors are discussed.
Fouling of polymeric membranes remains a major challenge for long‐term operation of oily‐water remediation. The common reclamation methods to recycle fouled membranes have the issues of either ...incomplete degradation of organic pollutants or damage to filter membranes. Here, a calcinable polymer membrane with effective reclamation after fouling is reported, which shows full recovery of the original oil/water separation efficiency. The membrane is made of polysulfonamide/polyacrylonitrile fibers by emulsion electrospinning, followed by hydrothermal decoration of TiO2 nanoparticles. The bonding structured fibrous membrane displays outstanding thermal stability in air (400 °C), strong acid/alkali resistance (at the pH range from 1 to 13), and robust tensile strength. As a result, the chemically fouled polymeric membrane can be easily reclaimed without decreasing in separation performance and mechanical properties by annealing treatment. As a proof‐of‐concept, the as‐prepared membrane is integrated into a wastewater separation tank, which achieves a high water flux over 3000 L m−2 h−1 and oil rejection efficiency of 99.6% for various oil‐in‐water emulsions. The presented strategy on membrane fabrication is believed to be an effective remedy for membrane fouling, and should apply in a wider field of filtration industry.
A calcinable polymer membrane with revivablility is rationally designed for oily‐water remediation. The interbonding structured TiO2@PSA/PAN fibrous membrane exhibits a high water flux, excellent separation efficiency, and robust thermal stability (400 °C). More importantly, the fouled membrane can be easily reclaimed without decrease in separation performance and mechanical property by annealing treatment.
Polymer doping is a significant approach to precisely control nucleation and crystal growth of perovskites and enhance electronic quality in perovskite solar cells (PSC) prepared in air. Here, a ...brand‐new self‐healing polysiloxane (SHP) with dynamic 2,6‐pyridinedicarboxamide (PDCA) coordination units and plenty of hydrogen bonds was designed and incorporated into perovskite films. PDCA units, showing strong intermolecular Pb2+‐Namido, I−‐Npyridyl, and Pb2+‐Oamido coordination interactions, were expected to enhance crystallinity and passivate the grain boundary. In addition, abundant hydrogen bonds in SHP afforded the self‐healing of cracks at grain boundaries for fatigue PSCs. Significantly, the doped device demonstrated a champion efficiency of 19.50 % with inconspicuous hysteresis, almost rivaling those achieved in control atmosphere. This strategy of heterocyclic‐based macromolecular doping in PSCs will pave a way for realizing efficient and durable crystalline semiconductors.
The perovskite solar cell (PSC) has emerged rapidly in the field of flexible photovoltaics. A self‐healing polysiloxane (SHP) polymer with pyridine‐based heterocyclic structures and plenty of dynamic hydrogen bonds was utilized to passivate and heal the cracks at grain boundaries. A champion efficiency of 19.50 % was achieved and the PSC with SHP recovered 80 % of original efficiency after self‐healing for 2 h in ambient atmosphere.
Solar evaporation through a photothermal porous material provides a feasible and sustainable method for water remediation. Several photothermal materials have been developed to enhance solar ...evaporation efficiency. However, a critical limitation of current photothermal materials is their inability to separate water from the volatile organic compounds (VOCs) present in wastewater. Here, a microstructured ultrathin polymeric membrane that enables freshwater separation from VOC pollutants by solar evaporation with a VOC removal rate of 90%, is reported. The different solution‐diffusion behaviors of water and VOCs with polymeric membranes facilitate their separation. Moreover, owing to increased light absorption, enlarged liquid–air interface, and shortened mass transfer distance, the microstructured and ultrathin configuration of the membrane helps to balance the tradeoff between permeation selectivity and water production capacity. The membrane is not only effective for evaporation of simulated volatile pollutants in a prototype, but can also intercept complex volatile organic contaminants in natural water sources and produce water that meets drinking‐water standards. With practical demonstration and satisfactory purification performance, this work paves the way for practical application of solar evaporation for effective water remediation.
A micropyramid‐structured PPy membrane with selective solution‐diffusion effect is employed as the photothermal material for solar water purification. The membrane is successful in intercepting the evaporation of volatile organic molecules in wastewater. Furthermore, its high light‐to‐heat conversion efficiency and good mechanical strength make the membrane a promising photothermal material for practical solar water purification.
Wearable healthcare presents exciting opportunities for continuous, real‐time, and noninvasive monitoring of health status. Even though electrochemical and optical sensing have already made great ...advances, there is still an urgent demand for alternative signal transformation in terms of miniaturization, wearability, conformability, and stretchability. Mechano‐based transductive sensing, referred to the efficient transformation of biosignals into measureable mechanical signals, is claimed to exhibit the aforementioned desirable properties, and ultrasensitivity. In this Concept, a focus on pressure, strain, deflection, and swelling transductive principles based on micro‐/nanostructures for wearable healthcare is presented. Special attention is paid to biophysical sensors based on pressure/strain, and biochemical sensors based on microfluidic pressure, microcantilever, and photonic crystals. There are still many challenges to be confronted in terms of sample collection, miniaturization, and wireless data readout. With continuing efforts toward solving those problems, it is anticipated that mechano‐based transduction will provide an accessible route for multimode wearable healthcare systems integrated with physical, electrophysiological, and biochemical sensors.
Mechano‐based transduction of biological signals has become an important route for wearable healthcare. This Concept provides an overview of recent advances, critical challenges, future development of pressure, strain, deflection, and swelling transductive principles for wearable healthcare devices. Special attention is paid to monitoring biophysical signals via pressure and strain sensors, and biochemical signals via microfluidic pressure, microcantilever, and photonic crystal sensors.
Ti2O3 nanoparticles with high performance of photothermal conversion are demonstrated for the first time. Benefiting from the nanosize and narrow‐bandgap features, the Ti2O3 nanoparticles possess ...strong light absorption and nearly 100% internal solar–thermal conversion efficiency. Furthermore, Ti2O3‐nanoparticle‐based thin film shows potential use in seawater desalination and purification.
Compared with traditional stimuli‐responsive devices with simple planar or tubular geometries, 3D printed stimuli‐responsive devices not only intimately meet the requirement of complicated shapes at ...macrolevel but also satisfy various conformation changes triggered by external stimuli at the microscopic scale. However, their development is limited by the lack of 3D printing functional materials. This paper demonstrates the 3D printing of photoresponsive shape memory devices through combining fused deposition modeling printing technology and photoresponsive shape memory composites based on shape memory polymers and carbon black with high photothermal conversion efficiency. External illumination triggers the shape recovery of 3D printed devices from the temporary shape to the original shape. The effect of materials thickness and light density on the shape memory behavior of 3D printed devices is quantified and calculated. Remarkably, sunlight also triggers the shape memory behavior of these 3D printed devices. This facile printing strategy would provide tremendous opportunities for the design and fabrication of biomimetic smart devices and soft robotics.
3D‐printed photoresponsive devices are successfully fabricated through combining fused deposition modeling and photoresponsive shape‐memory composites based on polyurethane and carbon black. This study demonstrates the shape‐memory behavior of these 3D‐printed devices is well triggered by sunshine. This development provides tremendous opportunities for customized stimuli‐responsive devices with complex geometric structure, which have potential in soft robots, selectively pliable tools, and orthopedic surgery.
Microbial fuel cell (MFC) can generate electricity from organic substances based on anodic electrochemically active microorganisms and cathodic oxygen reduction reaction (ORR), thus exhibiting ...promising potential for harvesting electric energy from organic wastewater. The ORR performance is crucial to both power production efficiency and overall cost of MFC. A new type of metal‐organic‐framework‐derived electrocatalysts containing cobalt and nitrogen‐doped carbon (CoNC) is developed, which is effective to enhance activity, selectivity, and stability toward four‐electron ORR in pH‐neutral electrolyte. When glucose is used as the substrate, the maximum power density of 1665 mW m−2 is achieved for the optimized CoNC pyrolyzed at 900 °C, which is 39.8% higher than that of 1191 mW m−2 for commercial Pt/C catalyst in the single‐chamber MFC. The improved performance of CoNC catalyst can be attributed to large surface area, microporous nature, and the involvement of nitrogen‐coordinated cobalt species. These properties enable the efficient ORR by increasing the active sites and enhancing mass transfer of oxygen and protons at “water‐flooding” three‐phase boundary where ORR occurs. This work provides a proof‐of‐concept demonstration of a noble‐metal‐free high‐efficiency and cost‐effective ORR electrocatalyst for effective recovery of electricity from biomass materials and organic wastewater in MFC.
A metal organic framework derived electrocatalyst (cobalt and N‐doped carbon, CoNC), prepared by direct pyrolysis of ZIF‐67, exhibits excellent activity, selectivity, and stability for oxygen reduction in pH‐neutral media. The CoNC, with large surface area, high ratio of micropores and uniform pore size, and abundant Co–Nx active sites in carbon matrix, enables 40% higher power density than a Pt/C catalyst in microbial fuel cells (MFC). The CoNC provides a new promising cathodic catalyst for more effective recovery of electric energy from organic wastewater and biomass materials in MFC.
Reducing the swelling of tissue‐adhesive hydrogels is crucial for maintaining stable tissue adhesion and inhibiting tissue inflammation. However, reported strategies for reducing swelling always ...result in a simultaneous decrease in the tissue adhesive strength of the hydrogel. Furthermore, once the covalent bonds break in the currently reported hydrogels, they cannot be rebuilt, and the hydrogel loses its tissue adhesive ability. In this work, a nonswelling hydrogel (named as “PAACP”) possessing regenerable high tissue adhesion is synthesized by copolymerizing and crosslinking poly(vinyl butyral) with acrylic acid, gelatin, and chitosan‐grafted N‐acetyl‐l‐cysteine. The tissue adhesive strength of the obtained PAACP reaches 211.4 kPa, which is approximately ten times higher than that of the reported nonswelling hydrogels, and the hydrogel can be reused for multiple cycles. The as‐prepared hydrogel shows great potential in soft bioelectronics, as muscle fatigue is successfully monitored via the electrode array and strain sensor integrated on PAACP substrates. The success of these bioelectronics offers potential applicability in the long‐term diagnosis of muscle‐related health conditions and prosthetic manipulations.
Nonswelling hydrogels with regenerable high wet tissue adhesion are fabricated. Subsequently, neural microelectrode arrays and rapid‐response strain sensors are integrated into the hydrogel to fabricate bifunctional tissue‐interface bioelectronics. Additionally, these bioelectronics possess excellent electrical properties. Electrocardiogram (ECG), electromyography (EMG), and tissue movement information are accurately recorded by the bioelectronics, and tissue fatigue is successfully monitored.
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