Illuminating the Brain: Advances and Perspectives in Optoelectronics for Neural Activity Monitoring and Modulation.

Optogenetic modulation of brain neural activity that combines optical and electrical modes in a unitary neural system has recently gained robust momentum. Controlling illumination spatial coverage, designing light-activated modulators, and developing wireless light delivery and data transmission are crucial for maximizing the use of optical neuromodulation. To this end, biocompatible electrodes with enhanced optoelectrical performance, device integration for multiplexed addressing, wireless transmission, and multimodal operation in soft systems have been developed. This review provides an outlook for uniformly illuminating large brain areas while spatiotemporally imaging the neural responses upon optoelectrical stimulation with little artifacts. Representative concepts and important breakthroughs, such as head-mounted illumination, multiple implanted optical fibers, and micro-light-delivery devices, are discussed. Examples of techniques that incorporate electrophysiological monitoring and optoelectrical stimulation are presented. Challenges and perspectives are posed for further research efforts toward high-density optoelectrical neural interface modulation, with the potential for nonpharmacological neurological disease treatments and wireless optoelectrical stimulation.

Plasma-Enabled Graphene Quantum Dot Hydrogel-Magnesium Composites as Bioactive Scaffolds for In Vivo Bone Defect Repair.

Bioactive and mechanically stable metal-based scaffolds are commonly used for bone defect repair. However, conventional metal-based scaffolds induce nonuniform cell growth, limiting damaged tissue restoration. Here, we develop a plasma nanotechnology-enhanced graphene quantum dot (GQD) hydrogel-magnesium (Mg) composite scaffold for functional bone defect repair by integrating a bioresource-derived nitrogen-doped GQD (NGQD) hydrogel into the Mg ZK60 alloy. Each scaffold component brings major synergistic advantages over the current alloy-based state of the art, including (1) mechanical support of the cortical bone and calcium deposition by the released Mg2+ during degradation; (2) enhanced uptake, migration, and distribution of osteoblasts by the porous hydrogel; and (3) improved osteoblast adhesion and proliferation, osteogenesis, and mineralization by the NGQDs in the hydrogel. Through an in vivo study, the hybrid scaffold with the much enhanced osteogenic ability induced by the above synergy promotes a more rapid, uniform, and directional bone growth across the hydrogel channel, compared with the control Mg-based scaffold. This work provides insights into the design of multifunctional hybrid scaffolds, which can be applied in other areas well beyond the demonstrated bone defect repair.

Human Skin-Inspired Electrospun Patterned Robust Strain-Insensitive Pressure Sensors and Wearable Flexible Light-Emitting Diodes.

Wearable skin-inspired electronic skins present remarkable outgrowth in recent years because their promising comfort device integration, lightweight, and mechanically robust durable characteristics led to significant progresses in wearable sensors and optoelectronics. Wearable electronic devices demand real-time applicability and factors such as complex fabrication steps, manufacturing cost, and reliable and durable performances, severely limiting the utilization. Herein, we nominate a scalable solution-processable electrospun patterned candidate capable of forming ultralong mechanically robust nano-microdimensional fibers with higher uniformity. Nanofibrous patterned substrates present surface energy and silver nanoparticle crystallization shifts, contributing to strain-sensitive and -insensitive conductive electrodes (10 000 cycles of 50% strain). Synergistic robust stress releasing and durable electromechanical behavior engenders stretchable durable health sensors, strain-insensitive pressure sensors (sensitivity of ∼83 kPa-1 and 5000 durable cycles), robust alternating current electroluminescent displays, and flexible organic light-emitting diodes (20% improved luminescence and 300 flex endurance of 2 mm bend radius).

Recent Progress in Conducting Polymer Composite/Nanofiber-Based Strain and Pressure Sensors.

The Conducting of polymers belongs to the class of polymers exhibiting excellence in electrical performances because of their intrinsic delocalized π- electrons and their tunability ranges from semi-conductive to metallic conductive regime. Conducting polymers and their composites serve greater functionality in the application of strain and pressure sensors, especially in yielding a better figure of merits, such as improved sensitivity, sensing range, durability, and mechanical robustness. The electrospinning process allows the formation of micro to nano-dimensional fibers with solution-processing attributes and offers an exciting aspect ratio by forming ultra-long fibrous structures. This review comprehensively covers the fundamentals of conducting polymers, sensor fabrication, working modes, and recent trends in achieving the sensitivity, wide-sensing range, reduced hysteresis, and durability of thin film, porous, and nanofibrous sensors. Furthermore, nanofiber and textile-based sensory device importance and its growth towards futuristic wearable electronics in a technological era was systematically reviewed to overcome the existing challenges.

Super Tough and Spontaneous Water-Assisted Autonomous Self-Healing Elastomer for Underwater Wearable Electronics.

Self-healing soft electronic material composition is crucial to sustain the device long-term durability. The fabrication of self-healing soft electronics exposed to high moisture environment is a significant challenge that has yet to be fully achieved. This paper presents the novel concept of a water-assisted room-temperature autonomous self-healing mechanism based on synergistically dynamic covalent Schiff-based imine bonds with hydrogen bonds. The supramolecular water-assisted self-healing polymer (WASHP) films possess rapid self-healing kinetic behavior and high stretchability due to a reversible dissociation-association process. In comparison with the pristine room-temperature self-healing polymer, the WASHP demonstrates favorable mechanical performance at room temperature and a short self-healing time of 1 h; furthermore, it achieves a tensile strain of 9050%, self-healing efficiency of 95%, and toughness of 144.2 MJ m-3 . As a proof of concept, a versatile WASHP-based light-emitting touch-responsive device (WASHP-LETD) and perovskite quantum dot (PeQD)-based white LED backlight are designed. The WASHP-LETD has favorable mechanical deformation performance under pressure, bending, and strain, whereas the WASHP-PeQDs exhibit outstanding long-term stability even over a period exceeding one year in a boiling water environment. This paper provides a mechanically robust approach for producing eco-friendly, economical, and waterproof e-skin device components.

Improving the Performance and Stability of Perovskite Light-Emitting Diodes by a Polymeric Nanothick Interlayer-Assisted Grain Control Process.

CsPbBr3 is a promising light-emitting material due to its wet solution processability, high photoluminescence quantum yield (PLQY), narrow color spectrum, and cost-effectiveness. Despite such advantages, the morphological defects, unsatisfactory carrier injection, and stability issues retard its widespread applications in light-emitting devices (LEDs). In this work, we demonstrated a facile and cost-effective method to improve the morphology, efficiency, and stability of the CsPbBr3 emissive layer using a dual polymeric encapsulation governed by an interface-assisted grain control process (IAGCP). An eco-friendly low-cost hydrophilic polymer poly(vinylpyrrolidone) (PVP) was blended into the CsPbBr3 precursor solution, which endows the prepared film with a better surface coverage with a smoothened surface. Furthermore, it is revealed that inserting a thin PVP nanothick interlayer at the poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/emissive layer interface further promotes the film quality and the performance of the derived LED. It is mainly attributed to three major consequences: (i) reduced grain size of the emissive layer, which facilitates charge recombination, (ii) reduced current leakage due to the enhanced electron-blocking effect, and (iii) improved color purity and air stability owing to better defect passivation. As a result, the optimized composite emissive film can retain the luminescence properties even on exposure to ambient conditions for 80 days and ∼62% of its initial PL intensity can be preserved after 30 days of storage without any encapsulation.

Facile Fabrication of Stretchable Touch-Responsive Perovskite Light-Emitting Diodes Using Robust Stretchable Composite Electrodes.

Perovskite light-emitting diode (PeLED) has been vigorously developed in recent years. As it has demonstrated good performance on the rigid substrates, the next important direction of PeLED is its integration with stretchable components to realize stretchable, responsive device. Here, we describe a facile fabrication of stretchable perovskite light-emissive touch-responsive devices (PeLETDs) by utilizing highly transparent and conductive polyurethane/silver nanowires (PU/AgNWs) as the electrode. Meanwhile, a stretchable tricomposite perovskite emissive layer was developed by blending a small amount of poly(ethylene oxide) (PEO) and poly(vinylpyrrolidone) (PVP) with CsPbBr3. Additionally, a thin PVP layer was introduced at the bottom of the emissive layer. On one hand, it can further improve the morphology of the emissive layer; on the other hand, it can serve as an electron-injection barrier to reduce the high nonradiative recombination at the corresponding interface. Further, to fulfill the responsive function of the fabricated PeLEDs, a poly(ethylene terephthalate) (PET) spacer with a 100 µm thickness was inserted between the top electrode and the emissive layer. A stretchable PeLETD is finally demonstrated to possess a low turn-on voltage of 2 V with a brightness of 380.5 cd m-2 at 7.5 V and can sustain 30% uniaxial strain with a small luminance variation of 24%. More interestingly, our stretchable PeLETD exhibited high stability, which could be well touch responsivity, where the luminance is on/off switched for 300 cycles by repeatedly applying pressure.

Conjugated Copolymers through Electrospinning Synthetic Strategies and Their Versatile Applications in Sensing Environmental Toxicants, pH, Temperature, and Humidity.

Conjugated copolymers (CCPs) are a class of polymers with excellent optical luminescent and electrical conducting properties because of their extensive π conjugation. CCPs have several advantages such as facile synthesis, structural tailorability, processability, and ease of device fabrication by compatible solvents. Electrospinning (ES) is a versatile technique that produces continuous high throughput nanofibers or microfibers and its appropriate synchronization with CCPs can aid in harvesting an ideal sensory nanofiber. The ES-based nanofibrous membrane enables sensors to accomplish ultrahigh sensitivity and response time with the aid of a greater surface-to-volume ratio. This review covers the crucial aspects of designing highly responsive optical sensors that includes synthetic strategies, sensor fabrication, mechanistic aspects, sensing modes, and recent sensing trends in monitoring environmental toxicants, pH, temperature, and humidity. In particular, considerable attention is being paid on classifying the ES-based optical sensor fabrication to overcome remaining challenges such as sensitivity, selectivity, dye leaching, instability, and reversibility.

Facile 3D Boron Nitride Integrated Electrospun Nanofibrous Membranes for Purging Organic Pollutants.

Elegant integration of three-dimensional (3D) boron nitride (BN) into the porous structure of a polymer nanofiber (NF) membrane system results in a surface with enhanced absorption capacity for removal. Various BN-based applications were designed and developed successfully, but BN-based absorption systems remain relatively unexplored. To develop a reusable absorption strategy with high removal efficiency, we used a composite of 3D BN and polyacrylonitrile (PAN) to prepare a NF membrane with a porous structure by using electrospinning and spray techniques (BN-PAN ES NFs). The removal efficiency of the 3D BN NF membrane was higher than that of a pure carbon NF membrane. Water pollutants, such as the dyes Congo red (CR), basic yellow 1 (BY), and rhodamine B (Rh B), were tested, and the absorption ratios were 46%, 53%, and 45%, respectively. Furthermore, the aforementioned dyes and pollutants can be completely eliminated and removed from water by heating because of the high heat resistance of 3D BN. The membrane can be recycled and reused at least 10 times. These results indicate that BN-PAN ES NFs have can be used in water purification and treatment for absorption applications, and that they can be reused after heat treatment.

Novel stretchable thermochromic transparent heaters designed for smart window defroster applications by spray coating silver nanowire.

A productive and novel method for fabricating stretchable transparent heaters with recognised thermochromic properties using commercially available thermochromic ink (TM-55-blue) and silver nanowire (AgNW)-coated polydimethylsiloxane (PDMS) is proposed. Lower resistance, elevated heat generation, and higher transparencies were the expected essential prerequisites for the fabrication of items such as smart windows and window defrosters. AgNW-coated PDMS (hereafter PH devices) satisfied the essential prerequisites but did not produce sufficient color change. In addition to the appreciable electrical and optical characteristics and mechanical robustness, observable color changes represent a critical factor in effortless temperature monitoring by the heating device. Blending TM-55-blue thermochromic ink with PDMS (PBH device) improves the heating rate and color transformation and promotes the ultralow response time appreciably. More notably, it produces a visible transformation from blue to colorless. Color changes visible to the naked eye, ultralow response time, and heating rate represent valuable features for deploying the PBH devices as window defrosters and in smart window applications.