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Gas diffusion layers (GDL) have become a critical component in electrochemical CO2 reduction (CO2R) systems because they can enable high current densities needed for industrially relevant productivity. Besides this function,...

Brain–machine interfaces typically rely on electrophysiological signals to interpret and transmit neurological information. In biological systems, however, neurotransmitters are chemical-based interneuron messengers. This mismatch can potentially lead to incorrect interpretation of the transmitted neuron information. Here we report a chemically mediated artificial neuron that can receive and release the neurotransmitter dopamine. The artificial neuron detects dopamine using a carbon-based electrochemical sensor and then processes the sensory signals using a memristor with synaptic plasticity, before stimulating dopamine release through a heat-responsive hydrogel. The system responds to dopamine exocytosis from rat pheochromocytoma cells and also releases dopamine to activate pheochromocytoma cells, forming a chemical communication loop similar to interneurons. To illustrate the potential of this approach, we show that the artificial neuron can trigger the controllable movement of a mouse leg and robotic hand. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version We acknowledge financial support from the National Key Research and Development Program of China (2017YFA0205302, L.W.); Natural Science Foundation of Jiangsu Province—Major Project (BK20212012, L.W.); National Key R&D Program of China (2021YFB3601200, M.W.); National Natural Science Foundation of China (81971701, B.H.); the Natural Science Foundation for Young Scholars of Jiangsu Province (BK20210596, T.W.); the Natural Science Foundation of Jiangsu Province (BK20201352, B.H.); the Program of Jiangsu Specially-Appointed Professor (B.H. and T.W.); Science Foundation of Nanjing University of Post and Telecommunications (NUPTSF, NY221004, T.W.); the Agency for Science, Technology and Research (A*STAR) under its AME Programmatic Funding Scheme (Project #A18A1b0045, X.C.); the National Research Foundation (NRF), Prime Minister’s Office, Singapore, under its NRF Investigatorship (NRF-NRFI2017-07, X.C.); and Singapore Ministry of Education (MOE2017-T2-2-107, X.C.).

Charging into epoxides Ethylene oxide is a strained, reactive molecule produced on a vast scale as a plastics precursor. The current method of synthesis involves the direct reaction of ethylene and oxygen at high temperature, but the original protocol relied on the reduction of chlorine to produce a chlorohydrin intermediate. Leow et al. report a room temperature method that returns to the chlorine route but uses electrochemistry to generate it catalytically from chloride (see the Perspective by Barton). This efficient process uses water in place of oxygen and can be integrated with the electrochemical generation of ethylene from carbon dioxide. Propylene oxide can be produced using the same method. Science , this issue p. 1228 ; see also p. 1181

There is significant interest in developing efficient electrochemical processes for commodity chemical manufacturing, all directly powered by renewable electricity. A vital chemical is ethylene glycol, with an annual consumption of around 20 million tonnes due to its use as antifreeze and as a polymer precursor. Here we report a one-step electrochemical route at ambient temperature and pressure in aqueous media to the selective partial oxidation of ethylene to ethylene glycol. Tuning of the catalyst OH binding energy was hypothesized to be crucial for facilitating the transfer of OH to *C2H4OH to form ethylene glycol. Computational studies suggested that a gold-doped palladium catalyst could perform this step efficiently, and experimentally we found it to exhibit an approximate 80% Faradaic efficiency to ethylene glycol, retaining its performance for 100 hours of continuous operation. These findings represent a significant advance in the development of selective anodic partial oxidation reactions in aqueous media under mild conditions. Ethylene glycol is a commodity chemical with an annual consumption of 20 million tonnes. Its production generates 1.6 tonnes of CO2 per tonne of ethylene glycol. To reduce these CO2 emissions, the authors report a one-step electrochemical route to selectively convert ethylene to ethylene glycol at ambient temperature and pressure in aqueous media.

The electrochemical performance of energy storage devices decreasing with the increase of charging/discharging rates is described as the Peukert’s effect. To minimize this effect, the reduction of the Peukert’s constant towards the ideal value of 1.0 is needed. Herein, for the first time, we reveal a correlation between the Peukert’s constant and the phase composition of electrode materials in lithium-ion batteries (LIBs). As a proof-of-concept, a parabola-like correlation is observed in the anatase/TiO2(B) electrode with a significant reduction in the Peukert’s constant from 2.15 to 1.20, when the content of anatase phase increases from 0% to 22%. This corresponds to a capacity enhancement of about three times from 42.2 to 131.5 mAh g–1 at a current density of 12.0 A g–1. The boosted charge-transfer kinetics in the composite electrode, relative to that of the single component electrode, is the cause for the reduction in the Peukert’s constant. Theoretical calculations well support the cooperative effect ...

We explore the selective electrocatalytic hydrogenation of lignin monomers to methoxylated chemicals, of particular interest, when powered by renewable electricity. Prior studies, while advancing the field rapidly, have so far lacked the needed selectivity: when hydrogenating lignin-derived methoxylated monomers to methoxylated cyclohexanes, the desired methoxy group (-OCH3) has also been reduced. The ternary PtRhAu electrocatalysts developed herein selectively hydrogenate lignin monomers to methoxylated cyclohexanes.molecules with uses in pharmaceutics. Using X-ray absorption spectroscopy and in situ Raman spectroscopy, we find that Rh and Au modulate the electronic structure of Pt and that this modulating steers intermediate energetics on the electrocatalyst surface to facilitate the hydrogenation of lignin monomers and suppress C-OCH3 bond cleavage. As a result, PtRhAu electrocatalysts achieve a record 58% faradaic efficiency (FE) toward 2-methoxycyclohexanol from the lignin monomer guaiacol at 200 mA cm(-2), representing a 1.9x advance in FE and a 4x increase in partial current density compared to the highest productivity prior reports. We demonstrate an integrated lignin biorefinery where wood-derived lignin monomers are selectively hydrogenated and funneled to methoxylated 2-methoxy-4-propylcyclohexanol using PtRhAu electrocatalysts. This work offers an opportunity for the sustainable electrocatalytic synthesis of methoxylated pharmaceuticals from renewable biomass.

The use of sunlight to drive organic reactions constitutes a green and sustainable strategy for organic synthesis. In such reactions, the photoredox requirements of organic reactions are typically fulfilled through using wide band gap semiconductors or redesigning the photocatalyst. Herein, we demonstrated the use of a reverse strategy; instead of redesigning the dye as per convention, the reactant is chemisorbed on the Brønsted base sites of Al2O3 to form a surface complex, causing an upshift in its HOMO to a level accessible for electron abstraction by the dye. This enables the highly selective oxidation of benzylic alcohols to aldehydes by a large variety of dyes, even though negligible reaction occurred in the absence of Al2O3 or with other metal oxides. The charge-transfer surface complex formed between the dye and Al2O3 is also essential in facilitating the transport of electrons from BnOH to O2. Next, we further extended the use of Al2O3 complexation in conjunction with photocatalysis to drive the selective aerobic oxidation of phenylboronic acids. It was discovered that all metal oxides with Brønsted basicity can also enable high yields of phenols. The proximity and strength of the Brønsted base sites appear to be crucial towards the reaction; there seems to be a positive relationship between the yields of alcohol and the quantity of strong Brønsted base sites, rather than with the quantity of weak or all Brønsted base sites. Lastly, we explored the idea of rendering Al2O3 photocatalytically active through carbon-modification, which would eliminate the need for a dye. The resultant carbon doped Al2O3 enables the selective oxidation of benzylic amines to form imines under visible light irradiation. We believe that our aforementioned discoveries may subvert our understanding of the role of Al2O3 in photocatalytic reactions. It may also bring forth a new methodology of utilizing surface complexation mechanisms between the reactants and earth-abundant materials to effectively achieve a wider range of photoredox reactions. Doctor of Philosophy (MSE)

Compared to transmission systems based on shafts and gears, tendon-driven systems offer a simpler and more dexterous way to transmit actuation force in robotic hands. However, current tendon fibers have low toughness and suffer from large friction, limiting the further development of tendon-driven robotic hands. Here, we report a super tough electro-tendon based on spider silk which has a toughness of 420 MJ/m3 and conductivity of 1,077 S/cm. The electro-tendon, mechanically toughened by single-wall carbon nanotubes (SWCNTs) and electrically enhanced by PEDOT:PSS, can withstand more than 40,000 bending-stretching cycles without changes in conductivity. Because the electro-tendon can simultaneously transmit signals and force from the sensing and actuating systems, we use it to replace the single functional tendon in humanoid robotic hand to perform grasping functions without additional wiring and circuit components. This material is expected to pave the way for the development of robots and various applications in advanced manufacturing and engineering., Tendon driven systems offer a simple way to transmit actuation force in robotic hands but current tendon fibres have low toughness, limiting the further development of tendon-driven actuators. Here the authors report a super tough electro-tendon based on spider silk, mechanically toughened by SWCNT and electrically enhanced by PEDOT:PSS.

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy. National Research Foundation (NRF) Accepted version This work was financially supported by the NTU-Northwestern Institute for Nanomedicine and the National Research Foundation, Prime Minister’s Office, Singapore, under the NRF Investigatorship (NRF-NRFI2017-07).

Producing liquid fuels such as ethanol from CO2, H2O, and renewable electricity offers a route to store sustainable energy. The search for efficient electrocatalysts for the CO2 reduction reaction relies on tuning the adsorption strength of carbonaceous intermediates. Here, we report a complementary approach in which we utilize hydroxide and oxide doping of a catalyst surface to tune the adsorbed hydrogen on Cu. Density functional theory studies indicate that this doping accelerates water dissociation and changes the hydrogen adsorption energy on Cu. We synthesize and investigate a suite of metal-hydroxide-interface-doped-Cu catalysts, and find that the most efficient, Ce(OH)x-doped-Cu, exhibits an ethanol Faradaic efficiency of 43% and a partial current density of 128 mA cm−2. Mechanistic studies, wherein we combine investigation of hydrogen evolution performance with the results of operando Raman spectroscopy, show that adsorbed hydrogen hydrogenates surface *HCCOH, a key intermediate whose fate determines branching to ethanol versus ethylene., Producing ethanol from carbon dioxide, water, and renewable electricity offers a route to sustainable energy. Here, the authors enhance electrocatalytic activity for carbon dioxide reduction by tuning adsorbed hydrogen in a class of copper catalysts with oxide- and hydroxide-modified surfaces.

Memristors constitute a promising functional component for information storage and in-memory computing in flexible and stretchable electronics including wearable devices, prosthetics, and soft robotics. Despite tremendous efforts made to adapt conventional rigid memristors to flexible and stretchable scenarios, stretchable and mechanical-damage-endurable memristors, which are critical for maintaining reliable functions under unexpected mechanical attack, have never been achieved. Here, the development of stretchable memristors with mechanical damage endurance based on a discrete structure design is reported. The memristors possess large stretchability (40%) and excellent deformability (half-fold), and retain stable performances under dynamic stretching and releasing. It is shown that the memristors maintain reliable functions and preserve information after extreme mechanical damage, including puncture (up to 100 times) and serious tearing situations (fully diagonally cut). The structural strategy offers new opportunities for next-generation stretchable memristors with mechanical damage endurance, which is vital to achieve reliable functions for flexible and stretchable electronics even in extreme and highly dynamic environments. Submitted/Accepted version T.W. and Z.C. contributed equally to this work. The project was supported by the National Research Foundation (NRF), Prime Minister’s office, Singapore, under its NRF Investigatorship (NRF-NRFI2017-07), Singapore Ministry of Education (MOE2017-T2-2-107 and MOE2019-T2-2-022), and the Agency for Science, Technology and Research (A*STAR) under its Advanced Manufacturing and Engineering (AME) Programmatic Funding Scheme (project #A18A1b0045).

Contact-mediated cell migration strongly determines the invasiveness of the corresponding cells, collective migration, and morphogenesis. The quantitative study of cellular response upon contact relies on cell-to-cell collision, which rarely occurs in conventional cell culture. Herein, we developed a strategy to activate a robust cell-to-cell collision within smooth muscle cell pairs. Nanomechanical traction force mapping reveals that the collision process is promoted by the oscillatory modulations between contraction and relaxation and orientated by the filopodial bridge composed of nanosized contractile machinery. This strategy can enhance the occurrence of cell-to-cell collision, which renders it advantageous over traditional methods that utilize micropatterned coating to confine cell pairs. Furthermore, modulation of the balance between cell tugging force and traction force can determine the repolarization of cells and thus the direction of cell migration. Overall, our approach could help to reveal the mechanistic contribution in cell motility and provide insights in tissue engineering. NRF (Natl Research Foundation, S’pore)

Exciting advancements have been made in the field of flexible electronic devices in the last two decades and will certainly lead to a revolution in peoples’ lives in the future. However, because of the poor sustainability of the active materials in complex stress environments, new requirements have been adopted for the construction of flexible devices. Thus, hierarchical architectures in natural materials, which have developed various environment-adapted structures and materials through natural selection, can serve as guides to solve the limitations of materials and engineering techniques. This review covers the smart designs of structural materials inspired by natural materials and their utility in the construction of flexible devices. First, we summarize structural materials that accommodate mechanical deformations, which is the fundamental requirement for flexible devices to work properly in complex environments. Second, we discuss the functionalities of flexible devices induced by nature-inspired structural materials, including mechanical sensing, energy harvesting, physically interacting, and so on. Finally, we provide a perspective on newly developed structural materials and their potential applications in future flexible devices, as well as frontier strategies for biomimetic functions. These analyses and summaries are valuable for a systematic understanding of structural materials in electronic devices and will serve as inspirations for smart designs in flexible electronics. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Stretchable devices, with the capability of retaining their functionalities under stretching, are drawing much attention as a promising solution to address the mechanical mismatch between traditional stiff electronics and soft curvilinear biological systems. Intensive efforts have been made toward the advancement of stretchable devices, such as the development of novel mechanically durable materials, deformable conductors and circuits, novel processing methods, and elastic matrixes for stretchable substrates and system integration. Among these, the elastic substrate constitutes the component that bears the applied strain and thus endows the device with stretchability, rendering its properties crucial to the overall performance of stretchable devices. This article provides a summary of the elastic materials commonly employed as stretchable substrates, as well as reveals fundamental insights into the properties requirements in the selection of stretchable substrates. Important challenges and strategies in the development of elastic matrices for stretchable devices are also discussed. Published version

The emulation of human sensation, perception, and action processes has become a major challenge for bioinspired intelligent robotics, interactive human-machine interfacing, and advanced prosthetics. Reflex actions, enabled through reflex arcs, are important for human and higher animals to respond to stimuli from environment without the brain processing and survive the risks of nature. An artificial reflex arc system that emulates the functions of the reflex arc simplifies the complex circuit design needed for "central-control-only" processes and becomes a basic electronic component in an intelligent soft robotics system. An artificial somatic reflex arc that enables the actuation of electrochemical actuators in response to the stimulation of tactile pressures is reported. Only if the detected pressure by the pressure sensor is above the stimulus threshold, the metal-organic-framework-based threshold controlling unit (TCU) can be activated and triggers the electrochemical actuators to complete the motion. Such responding mechanism mimics the all-or-none law in the human nervous system. As a proof of concept, the artificial somatic reflex arc is successfully integrated into a robot to mimic the infant grasp reflex. This work provides a unique and simplifying strategy for developing intelligent soft robotics, next-generation human-machine interfaces, and neuroprosthetics. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

Defects can greatly optimize the solar light harvesting capability and electronic structure of oxide materials. However, it remains challenging to achieve a defect engineering strategy under mild conditions. Meanwhile, the simultaneous exploitation of photogenerated holes (h+) and electrons (e−) to promote both photooxidation and photoreduction in a coupled system has rarely been reported. For the first time, we reveal an oxygen-vacancies-mediated photocatalytic strategy in which the electrons and holes are fully utilized for nitrobenzene reduction coupled with benzyl alcohol oxidation. The oxygen vacancies (OVs) generated in situ on the surface of TiO2 greatly extend light absorption into the visible region and promote the photogenerated electron transport for efficient photocatalysis. The experimental and theoretical results together indicate that chemisorption on the TiO2 surface decreases the oxidation potential of benzyl alcohol and causes an upward shift in its HOMO, which facilitates the oxidation reaction of benzyl alcohol to benzaldehyde. The in situ generated surface OVs also act as a bridge to enable the trapping and transferring of the photoinduced electrons to the nitrobenzene. This work provides a new perspective of utilizing the chemisorption between the reactant and catalyst to achieve a defect engineering strategy for synergetic photocatalysis. Accepted version

MoS2 holds great promise as high-rate electrode for lithium-ion batteries since its large interlayer can allow fast lithium diffusion in 3.0-1.0 V. However, the low theoretical capacity (167 mAh g-1 ) limits its wide application. Here, by fine tuning the lithiation depth of MoS2 , we demonstrate that its parent layered structure can be preserved with expanded interlayers while cycling in 3.0-0.6 V. The deeper lithiation and maintained crystalline structure endows commercially micrometer-sized MoS2 with a capacity of 232 mAh g-1 at 0.05 A g-1 and circa 92 % capacity retention after 1000 cycles at 1.0 A g-1 . Moreover, the enlarged interlayers enable MoS2 to release a capacity of 165 mAh g-1 at 5.0 A g-1 , which is double the capacity obtained under 3.0-1.0 V at the same rate. Our strategy of controlling the lithiation depth of MoS2 to avoid fracture ushers in new possibilities to enhance the lithium storage of layered transition-metal dichalcogenides. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version This work was supported by Singapore MOE Tier 2 (MOE2015-T2-1–110), Singapore National Research Foundation (Nanomaterials for Energy and Water Management CREATE Programme).

MoS

Flexible electronic devices are necessary for applications involving unconventional interfaces, such as soft and curved biological systems, in which traditional silicon-based electronics would confront a mechanical mismatch. Biological polymers offer new opportunities for flexible electronic devices by virtue of their biocompatibility, environmental benignity, and sustainability, as well as low cost. As an intriguing and abundant biomaterial, silk offers exquisite mechanical, optical, and electrical properties that are advantageous toward the development of next-generation biocompatible electronic devices. The utilization of silk fibroin is emphasized as both passive and active components in flexible electronic devices. The employment of biocompatible and biosustainable silk materials revolutionizes state-of-the-art electronic devices and systems that currently rely on conventional semiconductor technologies. Advances in silk-based electronic devices would open new avenues for employing biomaterials in the design and integration of high-performance biointegrated electronics for future applications in consumer electronics, computing technologies, and biomedical diagnosis, as well as human-machine interfaces.

The emergence of drug-resistant microbes has become a threat to global health, and microbial infections severely limit the use of healthcare materials. To achieve efficient antimicrobial therapy, supramolecular hydrogels demonstrate unprecedented advantages in medical applications due to the tunable and reversible nature of their supramolecular interactions and the capability of hydrogels to incorporate various therapeutic agents. Herein, antimicrobial hydrogels are categorized according to their inherent antimicrobial properties or based on their roles in encapsulating antimicrobial materials. Moreover, strategies to further enhance the antimicrobial efficacy of hydrogels are highlighted, such as the incorporation of antifouling agents or the enabling of response towards physiological cues. We envision that supramolecular hydrogels, in combination with modern medical technology and devices, will contribute to the development of efficient and safe systems for antimicrobial therapy. NRF (Natl Research Foundation, S’pore) Accepted version

The reciprocal mechanical interaction of engineered materials with biointerfaces have long been observed and exploited in biomedical applications. It contributes to the rise of biomechano-responsive materials and biomechano-stimulatory materials, constituting the biomechano-interactive interfaces. Here, endogenous and exogenous biomechanical stimuli available for mechanoresponsive interfaces are briefed and their mechanistic responses, including deformation and volume change, mechanomanipulation of physical and chemical bonds, dissociation of assemblies, and coupling with thermoresponsiveness are summarized. The mechanostimulatory materials, however, are capable of delivering mechanical cues, including stiffness, viscoelasticity, geometrical constraints, and mechanical loads, to modulate physiological and pathological behaviors of living tissues through the adaptive cellular mechanotransduction. The biomechano-interactive materials and interfaces are widely implemented in such fields as mechanotriggered therapeutics and diagnosis, adaptive biophysical sensors, biointegrated soft actuators, and mechanorobust tissue engineering, which have offered unprecedented opportunities for precision and personalized medicine. Pending challenges are also addressed to shed a light on future advances with respect to translational implementations. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Tactile sensors capable of perceiving biophysical signals such as force, pressure, or strain have attracted extensive interest for versatile applications in electronic skin, noninvasive healthcare, and biomimetic prostheses. Despite these great achievements, they are still incapable of detecting bio/chemical signals that provide even more meaningful and precise health information due to the lack of efficient transduction principles. Herein, a tactile chemomechanical transduction strategy that enables the tactile sensor to perceive bio/chemical signals is proposed. In this methodology, pyramidal tactile sensors are linked with biomarker‐induced gas‐producing reactions, which transduce biomarker signals to electrical signals in real time. The method is advantageous as it enhances electrical signals by more than tenfold based on a triple‐step signal amplification strategy, as compared to traditional electrical biosensors. It also constitutes a portable and general platform capable of quantifying a wide spectrum of targets including carcinoembryonic antigen, interferon‐γ, and adenosine. Such tactile chemomechanical transduction would greatly broaden the application of tactile sensors toward bio/chemical signals perception which can be used in ultrasensitive portable biosensors and chemical‐responsive chemomechanical systems. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Soft and stretchable electronic devices are important in wearable and implantable applications because of the high skin conformability. Due to the natural biocompatibility and biodegradability, silk protein is one of the ideal platforms for wearable electronic devices. However, the realization of skin-conformable electronic devices based on silk has been limited by the mechanical mismatch with skin, and the difficulty in integrating stretchable electronics. Here, silk protein is used as the substrate for soft and stretchable on-skin electronics. The original high Young's modulus (5-12 GPa) and low stretchability ( 400%, respectively. This plasticization is realized by the addition of CaCl2 and ambient hydration, whose mechanism is further investigated by molecular dynamics simulations. Moreover, highly stretchable (>100%) electrodes are obtained by the thin-film metallization and the formation of wrinkled structures after ambient hydration. Finally, the plasticized silk electrodes, with the high electrical performance and skin conformability, achieve on-skin electrophysiological recording comparable to that by commercial gel electrodes. The proposed skin-conformable electronics based on biomaterials will pave the way for the harmonized integration of electronics into human. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

Photoredox catalysis provides opportunities in harnessing clean and green resources such as sunlight and O2 , while the acid and base surface sites of metal oxides are critical for industrial catalysis such as oil cracking. The contribution of metal oxide surfaces towards photocatalytic aerobic reactions was elucidated, as demonstrated through the hydroxylation of boronic acids to alcohols. The strength and proximity of the surface base sites appeared to be two key factors in driving the reaction; basic and amphoteric oxides such as MgO, TiO2 , ZnO, and Al2 O3 enabled high alcohol yields, while acidic oxides such as SiO2 and B2 O3 gave only low yields. The reaction is tunable to different irradiation sources by merely selecting photosensitizers of compatible excitation wavelengths. Such surface complexation mechanisms between reactants and earth abundant materials can be effectively utilized to achieve a wider range of photoredox reactions. MOE (Min. of Education, S’pore) Accepted version

Highly stretchable microsupercapacitors with stable electrochemical performance are fabricated. Their excellent stretchable and electrochemical performance relies on the suspended wavy structures of graphene microribbons. This avoids the detachment and cracks of the electrode materials. In addition, it ensures the electrode fingers keep a relatively constant distance so the stability of the microsupercapacitors can be enhanced.

A simple and portable colorimetric assay for creatinine detection is fabricated based on the synergistic coordination of creatinine and uric acid with Hg(2+) on the surface of gold nanoparticles, which exhibits good selectivity and sensitivity. Point-of-care clinical creatinine monitoring can be supported for monitoring renal function and diagnosing corresponding renal diseases at home.

The employ of natural biomaterials as the basic building blocks of electronic devices is of growing interest for biocompatible and green electronics. Here, resistive switching (RS) devices based on naturally silk protein with configurable functionality are demonstrated. The RS type of the devices can be effectively and exactly controlled by controlling the compliance current in the set process. Memory RS can be triggered by a higher compliance current, while threshold RS can be triggered by a lower compliance current. Furthermore, two types of memory devices, working in random access and WORM modes, can be achieved with the RS effect. The results suggest that silk protein possesses the potential for sustainable electronics and data storage. In addition, this finding would provide important guidelines for the performance optimization of biomaterials based memory devices and the study of the underlying mechanism behind the RS effect arising from biomaterials.

Resistive switching memory constitutes a prospective candidate for next-generation data storage devices. Meanwhile, naturally occurring biomaterials are promising building blocks for a new generation of environmentally friendly, biocompatible, and biodegradable electronic devices. Recent progress in using proteins to construct resistive switching memory devices is highlighted. The protein materials selection, device engineering, and mechanism of such protein-based resistive switching memory are discussed in detail. Finally, the critical challenges associated with protein-based resistive switching memory devices are presented, as well as insights into the future development of resistive switching memory based on natural biomaterials.

Single-crystalline rutile TiO2 nano-flower hierarchical structures were synthesized via a one-pot solvent-thermal method, and they are demonstrated to be ordered three dimensional (3D) hierarchical structures with single-crystalline rutile TiO2 nanorods as building blocks. They exhibited enhanced photocatalytic activity for the selective oxidation from benzylamine to N-benzylidenebenzylamine (N-BIBL) with high yield under visible light irradiation. Such a remarkable performance could be attributed to the rapid photocharge separation and inhibition of charge recombination due to the unique hierarchical structures of this single-crystalline rutile TiO2 nano-flower. The facilely prepared single-crystalline rutile TiO2 nano-flowers are promising materials in the field of photocatalytic fine chemical conversions and other photocatalytic applications.

A detailed understanding of chemotherapy is determined by the response of cell to the formation of the drug-target complex and its corresponding sudden or eventual cell death. However, visualization of this early but important process, encompassing the fast dynamics as well as complex network of molecular pathways, remains challenging. Herein, we report that the nanomechanical traction force is sensitive enough to reflect the early cellular response upon the addition of chemotherapeutical molecules in a real-time and noninvasive manner, due to interactions between chemotherapeutic drug and its cytoskeleton targets. This strategy has outperformed the traditional cell viability, cell cycle, cell impendence as well as intracellular protein analyses, in terms of fast response. Furthermore, by using the nanomechanical traction force as a nanoscale biophysical marker, we discover a cellular nanomechanical change upon drug treatment in a fast and sensitive manner. Overall, this approach could help to reveal the hidden mechanistic steps in chemotherapy and provide useful insights in drug screening. NRF (Natl Research Foundation, S’pore) Accepted version

Polymeric microelectrode arrays (MEAs) are emerging as a new generation of biointegrated microelectrodes to transduce original electrochemical signals in living tissues to external electrical circuits, and vice versa. So far, the challenge of stretchable polymeric MEAs lies in the competition between high stretchability and good electrode-substrate adhesion. The larger the stretchability, the easier the delamination of electrodes from the substrate due to the mismatch in their Young's modulus. In this work, polypyrrole (PPy) electrode materials are designed, with PPy nanowires integrated on the high conductive PPy electrode arrays. By utilizing this electrode material, for the first time, stretchable polymeric MEAs are fabricated with both high stretchability (≈100%) and good electrode-substrate adhesion (1.9 MPa). In addition, low Young's modulus (450 kPa), excellent recycling stability (10 000 cycles of stretch), and high conductivity of the MEAs are also achieved. As a proof of concept, the as-prepared polymeric MEAs are successfully used for conformally recording the electrocorticograph signals from rats in normal and epileptic states, respectively. Further, these polymeric MEAs are also successful in stimulating the ischiadic nerve of the rat. This strategy provides a new perspective to the highly stretchable and mechanically stable polymeric MEAs, which are vital for compliant neural electrodes. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Animals possess various functional systems such as sensory, nervous, and motor systems, which show effective cooperation in order to realize complicated and intelligent behaviors. This inspires rational designs for the integration of individual electronic devices to exhibit a series of functions, such as sensing, memory, and feedback. Inspired by the fact that humans can monitor and memorize various body motions, a motion memory device is developed to mimic this biological process. In this work, mechanical hybrid substrates are introduced, in which rigid memory devices and stretchable strain sensors are integrated into a single module, which enables them to work cooperatively in the wearable state. When attached to the joints of limbs, the motion memory device can detect the deformations caused by limb motions and simultaneously store the corresponding information in the memory device. This work would be valuable in materials design and electronics technology toward the realization of wearable and multifunctional electronic modules. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Re-epithelialization by collective migration of epithelial cells over a heterogeneous environment to restore tissue integrity and functions is critical for development and regeneration. Here, it is reported that the spatial organization of adjacent adherent paths within sparsely distributed extracellular matrix (ECM) has a significant impact on the orientational coupling between cell polarization and collective cell migration. This coupling effect determines the migration pattern for human keratinocytes to regain their cohesion, which impacts the occupancy of epithelial bridge and the migration velocity in wound repair. Statistical studies suggest the converging organization of ECM, in which adjacent paths become closer to each other and finally converge to a junctional point, facilitating collective cell migration mostly within variable ECM organization, as the polarization of the advancing cell sheet is remodeled to align along the direction of cell migration. The findings may help to design implantable ECM to optimize efficient skin regeneration. NRF (Natl Research Foundation, S’pore) Accepted version

The use of sunlight to drive organic reactions constitutes a green and sustainable strategy for organic synthesis. Herein, we discovered that the earth-abundant aluminum oxide (Al2O3) though paradigmatically known to be an insulator could induce an immense increase in the selective photo-oxidation of different benzyl alcohols in the presence of a large variety of dyes and O2. This unique phenomenon is based on the surface complexation of benzyl alcohol (BnOH) with the Brønsted base sites on Al2O3, which reduces its oxidation potential and causes an upshift in its HOMO for electron abstraction by the dye. The surface complexation of O2 with Al2O3 also activates the adsorbed O2 for receiving electrons from the photoexcited dyes. This discovery brings forth a new understanding on utilizing surface complexation mechanisms between the reactants and earth abundant materials to effectively achieve a wider range of photoredox reactions. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

Programmable polymer substrates, which mimic the variable extracellular matrices in living systems, are used to regulate multicellular morphology, via orthogonally modulating the matrix topography and elasticity. The multicellular morphology is dependent on the competition between cell-matrix adhesion and cell-cell adhesion. Decreasing the cell-matrix adhesion provokes cytoskeleton reorganization, inhibits lamellipodial crawling, and thus enhances the leakiness of multicellular morphology.

Programmable photocatalysts for hydrogen evolution have been fabricated based on multi-segmented CdS-Au nanorod arrays, which exhibited high-efficiency and programmability in hydrogen evolution as the photoanodes in the photoelectrochemical cell. Multiple different components each possess unique physical and chemical properties that provide these cascade nanostructures with multiformity, programmability, and adaptability. These advantages allow these nanostructures as promising candidates for high efficient harvesting and conversion of solar energy.

Organic nanofibers are formed by simple ionic co-assembly of positively charged porphyrin (electron donor) and negatively charged perylenediimide (electron acceptor) derivatives in aqueous solution. Two kinds of electron transfer routes between electron donor and electron acceptor under light excitation in nanofibers are confirmed by DFT calculations and experimental data.

A large amount of evidence has demonstrated the revolutionary role of nanosystems in the screening and shielding of biological systems. The explosive development of interfacing bioentities with programmable nanomaterials has conveyed the intriguing concept of nano-bio interfaces. Here, recent advances in functional biointegrated devices through the precise programming of nano-bio interactions are outlined, especially with regard to the rational assembly of constituent nanomaterials on multiple dimension scales (e.g., nanoparticles, nanowires, layered nanomaterials, and 3D-architectured nanomaterials), in order to leverage their respective intrinsic merits for different functions. Emerging nanotechnological strategies at nano-bio interfaces are also highlighted, such as multimodal diagnosis or "theragnostics", synergistic and sequential therapeutics delivery, and stretchable and flexible nanoelectronic devices, and their implementation into a broad range of biointegrated devices (e.g., implantable, minimally invasive, and wearable devices). When utilized as functional modules of biointegrated devices, these programmable nano-bio interfaces will open up a new chapter for precision nanomedicine.

As emerging efficient emitters, metal-halide perovskites offer the intriguing potential to the low-cost light emitting devices. However, semiconductors generally suffer from severe luminescence quenching due to insufficient confinement of excitons (bound electron-hole pairs). Here, Sn-triggered extrinsic self-trapping of excitons in bulk 2D perovskite crystal, PEA2 PbI4 (PEA = phenylethylammonium), is reported, where exciton self-trapping never occurs in its pure state. By creating local potential wells, isoelectronic Sn dopants initiate the localization of excitons, which would further induce the large lattice deformation around the impurities to accommodate the self-trapped excitons. With such self-trapped states, the Sn-doped perovskites generate broadband red-to-near-infrared (NIR) emission at room temperature due to strong exciton-phonon coupling, with a remarkable quantum yield increase from 0.7% to 6.0% (8.6 folds), reaching 42.3% under a 100 mW cm-2 excitation by extrapolation. The quantum yield enhancement stems from substantial higher thermal quench activation energy of self-trapped excitons than that of free excitons (120 vs 35 meV). It is further revealed that the fast exciton diffusion involves in the initial energy transfer step by transient absorption spectroscopy. This dopant-induced extrinsic exciton self-trapping approach paves the way for extending the spectral range of perovskite emitters, and may find emerging application in efficient supercontinuum sources. Ministry of Education (MOE) Accepted version J.Y., J.K., and W.H. contributed equally to this work. The authors acknowledge the financial support from Singapore MOE (MOE2014-T2-2-140 and MOE2014-T3-1-004). The authors also thank the partial financial support from the National Natural Science Foundation of China (No. 51402259), “100 Talents Program” of Fujian Province, the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB20000000), the CAS/SAFEA International Partnership Program for Creative Research Teams, and the International Postdoctoral Exchange Program.