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In recent years, flexible stress sensors capable of monitoring diverse body movements and physiological signals have been attracting great attention in the fields of healthcare systems, human–machine interfaces, and wearable electronics. Inspired by the structure of natural eggshell inner membrane (ESIM), we developed a pressure sensor based on MXene (Ti3C2Tx)/Ag NWs (silver nanowires) composite electrodes and the micro-structured dielectric layer to meet the application requirements of wide detection range and long-term stability for the sensors. In the light of the nanoscale-microarray of the dielectric layer and the rough surface of electrode materials, this pressure sensor is expected to allow great and persistent deformation during the loading process. As a result, the device is characterized by an improved sensitivity, fast response (in the millisecond range), wide detection range (0–600 kPa), and long-term stability. The outstanding performance of the proposed sensor makes it possible to detect various human activities, such as speaking, air blowing, clenching, walking, finger/knee/elbow bending, and striking, demonstrating its good application prospects in wearable and flexible electronic devices.

An effective and simple method to solve nonlinear evolution partial differential equations is the self-similarity transformation, in which one utilizes solutions of the known equation to find solutions of the unknown. In this paper, we employ an improved similarity transformation to transform the $$(2+1)$$-dimensional (D) sine-Gordon (SG) equation into the $$(1+1)$$-D SG equation and obtain non-rational solutions of the $$(2+1)$$-D SG equation by utilizing the known solutions of the $$(1+1)$$-D SG equation. Based on the solutions obtained, and with the help of special choices of the involved solution parameters, several localized structures of the $$(2+1)$$-D SG model are analyzed on a finite background, such as the embedded hourglass, split silo, dumbbell, and pie solitons. Their spatiotemporal profiles are displayed, and their properties are discussed.

The rational design and scalable assembly of nanoarchitectures are important to deliver highly uniform, functional films with high performance. However, fabrication of large-area and high-performance films is quite difficult because of the challenges in controlling homogeneous microstructures, interface properties, and the high cost of the conventional vacuum deposition technique. Here, we report a solution-processed molecular level assembly approach to fabricate self-supported (without any binders or conductive additives) large-area (up to 810 cm ) functional films with controllable thickness and high homogeneity. We show that the assembled prototypical Fe(II)-based metallo-supramolecular polymer (polyFe) film exhibits unprecedented electrochromic performance such as ultrahigh coloration efficiency (750.3 cm C ), fast switching speed (

Graphene nanosheet films (GNSF) show great potential as solid lubricants. They, however, usually suffer from short lifetime and low load capability, limiting their further engineering application. In this work, we try to address these crucial challenges, for the first time, by inducing a unique three-dimensional microstructure into the GNSF. The as-prepared three-dimensional graphene nanosheet films (3D-GNSF) are composed of many crumpled and partially standing graphene nanosheets (GNS) that overlap with each other and form a three-dimensional interconnected network. The morphology, composition and structure of the 3D-GNSF are investigated in detail using scanning electron microscope, X-ray diffractometer, transmission electron microscope and X-ray photoelectron spectroscopy to deduce their possible formation mechanism. Tribological tests are conducted in air as a function of contact pressure that is up to about 1GPa. The results suggest it is the unique architecture of the 3D-GNSF that quickly produces a compact and stable sliding interface consisting of GNS against GNS, enabling 3D-GNSF as promising solid lubricants with low friction, excellent anti-wear ability, good durability and high load capability. The authors are grateful to the National Natural Science Foundation of China (51605097) and Training Programs of Innovation and Entrepreneurship for Undergraduates (201811845148) for financial support.

The medical diagnosis of Parkinson’s disease (PD) mainly relies on doctors’ clinical experience and scoring scales, which may lead to erroneous judgments due to the differences of their clinical experience. Gait information, such as postural instability and bradykinesia, is a common symptom in PD. Gait analysis and classification is often adopted as a clinical tool for detecting and diagnosing PD. In this paper, gait parameters are collected from 200 PD patients and 100 healthy controls (HC) through the wearable sensors, which include 95 features. Considering the redundancy between the features, F -test and Recursive Feature Elimination (RFE) methods are utilized for feature selection. Moreover, support vector machine (SVM) algorithm is utilized to train the classifier, which can automatically classify PD patients and HC. Furthermore, experiments on the class-imbalance and class-equilibrium samples are performed to verify the reliability and stability of the above methods. Compared with all feature based SVM and F -test based SVM, the RFE-based SVM has better performance, where the accuracy, sensitivity and specificity are 96.67%, 96.77% and 96.55%, respectively. The results show that the RFE-based SVM classifier can well distinguish PD and healthy gait, and can effectively assist doctors to diagnose PD in clinical practice, thus breaking the subjectivity brought by traditional PD diagnosis.

Vital signal monitoring is conducive to the diagnosis of a variety of diseases, which can be used to learn patients’ health status. To avoid cross infection (for example infectious diseases), non-contact vital sign detection has attracted more and more attention. In this paper, an important hospital scenario, i.e., the medical staff and infectious disease patients are separated by glass wall, is considered. Under the considered scenario, an through-and-wall impulse radio ultra-wideband (IR-UWB) system placed on the room of the medical staff is adopted to obtain the information of the patient’s heart rate and breathing rate, thus cutting off direct contact between the medical staff and infectious disease patients. To this end, the basic idea is that the received through-and-wall IR-UWB echo signal is subtracted to the environmental noise via a background noise removal method, then an modified two-dimension ensemble empirical mode decomposition (EEMD) method is proposed to analyze the remained echo signal, thus obtaining respiration rate and heartbeat rate. Compared with the conventional two-dimension EEMD, the modified two-dimension EEMD method has lower complexity and increases the computational speed. The experimental results of the proposed method show that the average errors of breathing and heart rates are 1.6% and 4.3%, respectively.

Electrochromic devices (ECDs) have a broad range of application prospects in many important energy efficient optoelectronic fields, such as smart windows, anti-glare rearview mirrors, low-energy displays, and infrared camouflage. However, there are some factors restricting their development, such as low coloration efficiency, slow switching speed, and poor cycling stability. Coordination polymer (CP) is a promising active material for the fabrication of high-performance ECD because of its ultrahigh coloration efficiency, fast switching speed, and excellent cycling stability. In this review, current advances of CP in energy efficient ECDs are comprehensively summarized and evaluated. Specifically, the effects of composition, coordination bonding, and microstructure of the bipyridine- and terpyridine-based CP on EC performances are introduced and discussed in detail. Then, the challenges and prospects of this booming field are proposed. Finally, the broad application prospects of the CPs-based EC materials and the corresponding devices are also demonstrated, which hold numerous revolutionary effects over our daily life. Hopefully, this review would provide useful guidance and further promote progress on the electrochromic and other optoelectronic fields.

Reversible electrochemical mirror (REM) electrochromic devices with electrochemical tunability in multiple optical states are exciting alternatives to conventional electrochromic smart windows. Electrochromic devices are studied extensively, yet widespread adoptions have not been achieved due to problems associated with durability, switching speed, limited options on optical states, and cost. In this study, a REM electrochromic device based on CuSn alloy is developed, which offers highly reversible switching between transparent, greyish‐blue, and mirror states via reversible electrodeposition and dissolution. The alloying element, Sn acts as an electrochemical mediator, which facilitates the electrodeposition and dissolution of Cu. The CuSn‐based REM device shows superior cycling stability for 2400 cycles (transmittance mode) and 1000 cycles (reflectance mode). The electrodeposited CuSn alloy film is resistant to surface oxidation in ambient air, with a 2.9% difference in reflectance at 2000 nm after 3 days. In addition, the alloy film exhibits excellent NIR reflectance property with thermal modulation of 18.5 °C at a high temperature of 180 °C. The REM device with zero power consumption maintains its mirror state for at least 100 min, making it a promising candidate for energy‐efficient applications., The quasi‐solid‐state tristate reversible electrochemical mirror (REM) device offers highly reversible switching between transparent, greyish‐blue, and mirror states via reversible electrodeposition and dissolution. The REM shows superior thermal barrier property compared to the bare substrate. The extended memory effect of the REM device is achieved in the presence of quasi‐solid‐state polymer electrolyte.

The rational design of previously unidentified materials that could realize excellent electrochemical‐controlled optical and charge storage properties simultaneously, are especially desirable and useful for fabricating smart multifunctional devices. Here, a facile synthesis of a 1D π–d conjugated coordination polymer (Ni‐BTA) is reported, consisting of metal (Ni)‐containing nodes and organic linkers (1,2,4,5‐benzenetetramine), which could be easily grown on various substrates via a scalable chemical bath deposition method. The resulting Ni‐BTA film exhibits superior performances for both electrochromic and energy storage functions, such as large optical modulation (61.3%), high coloration efficiency (223.6 cm2 C−1), and high gravimetric capacity (168.1 mAh g−1). In particular, the Ni‐BTA film can maintain its electrochemical recharge‐ability and electrochromic properties even after 10 000 electrochemical cycles demonstrating excellent durability. Moreover, a smart energy storage indicator is demonstrated in which the energy storage states can be visually recognized in real time. The excellent electrochromic and charge storage performances of Ni‐BTA films present a great promise for Ni‐BTA nanowires to be used as practical electrode materials in various applications such as electrochromic devices, energy storage cells, and multifunctional smart windows., A 1D π–d conjugated coordination polymer (CCP) is successfully fabricated in which specific organic linker and metal ions are selected with the aim of increasing the density of redox active centers and enabling conductive paths for charge transport. Moreover, this CCP enables dual electrochromic and energy storage functionalities in an integrated smart device.

The emergence of soft energy devices provides new possibilities for various applications, it also creates significant challenges in the selection of structural design and material compatibility. Herein, we demonstrate a stretchable transmissive electrochromic energy storage device by inkjet-printing single layer of WO3 nanoparticles on an elastomeric transparent conductor. Such hybrid electrode is highly conductive and deformable, making it an excellent candidate for the application: large optical modulation of 40%, fast switching speed (

High-quality patterns were successfully prepared by inkjet-printing WO3-PEDOT:PSS composites on different substrates including the rigid FTO glass and most importantly, on flexible PEDOT:PSS/Ag grid/PET. Excellent electrochromic performances can be achieved, including large optical modulation (85.7% optical contrast at the wavelength of 633 nm on FTO glass substrate), fast switching speed (coloration/bleaching time of 2.4/0.8 s on the PEDOT:PSS/Ag grid/PET substrate), instantaneous coloration efficiency (68.8 cm2 C−1) and good cycling stability (up to 10,000 cycles). The effects of the applied potential window during electrochemical evaluation on the electrochromic performances were analyzed in detail. The printed electrochromics films on PEDOT:PSS/Ag grid/PET showed the best electrochemical stability, in agreement with its superior conductivity and transmittance at 633 nm of 0.6 Ω/sq and 66%, respectively. It sustained transmittance modulation of about 75.5% and 53.1% of its first cycle recorded contrast at 633 nm, after being subjected to 1000 and 5000 cycles, respectively, and maintained good electrochemical stability up to 10,000 cycles. Moreover, a robust mechanical stability was also achieved by the printed films on flexible PEDOT:PSS/Ag grid/PET substrate. The film maintained a transmittance modulation of 85.8% of its original contrast after 5000 bending cycles at a curvature radius of 1 cm. The inkjet-printed WO3 nanocomposite based flexible electrochromic displays exhibited excellent electrochromic performance, making it a promising candidate for energy efficient displays, e-books, e-cards and multifunctional electronic devices. NRF (Natl Research Foundation, S’pore)

Spatially coupled protograph (SC-P) low-density parity-check codes can achieve excellent performance and simple implementation when the coupling length is sufficiently large. However, in the case of small coupling lengths, terminated SC-P (TE-SC-P) codes suffer from relatively weaker decoding thresholds and lower code rates compared with the original protograph codes. To address the above issues, we propose a novel design method to enhance the performance of such TE-SC-P codes. Specifically, we develop a bus-topology-like puncturing rule so as to formulate a new family of SC-P codes, referred to as punctured TE-SC-P (P-TE-SC-P) codes . Theoretical analyses and simulation results show that the proposed P-TE-SC-P codes possess significant performance gains over conventional SC-P codes and randomly punctured TE-SC-P (called RP-TE-SC-P) codes with relatively higher computational complexity.

An unprecedented MXene-based actuator was developed, which mimicked the sophisticated leaf structure and its functionality., Natural leaves, with elaborate architectures and functional components, harvest and convert solar energy into chemical fuels that can be converted into energy based on photosynthesis. The energy produced leads to work done that inspired many autonomous systems such as light-triggered motion. On the basis of this nature-inspired phenomenon, we report an unprecedented bilayer-structured actuator based on MXene (Ti3C2Tx)–cellulose composites (MXCC) and polycarbonate membrane, which mimic not only the sophisticated leaf structure but also the energy-harvesting and conversion capabilities. The bilayer actuator features multiresponsiveness, low-power actuation, fast actuation speed, large-shape deformation, programmable adaptability, robust stability, and low-cost facile fabrication, which are highly desirable for modern soft actuator systems. We believe that these adaptive soft systems are attractive in a wide range of revolutionary technologies such as soft robots, smart switch, information encryption, infrared dynamic display, camouflage, and temperature regulation, as well as human-machine interface such as haptics.

Transparent nonvolatile memory has great potential in integrated transparent electronics. Here, we present highly transparent resistive switching memory using stoichiometric WO3 film produced by cathodic electrodeposition with indium tin oxide electrodes. The memory device demonstrates good optical transmittance, excellent operative uniformity, low operating voltages (+0.25 V/–0.42 V), and long retention time (>104 s). Conductive atomic force microscopy, ex situ transmission electron microscopy, and X-ray photoelectron spectroscopy experiments directly confirm that the resistive switching effects occur due to the electric field-induced formation and annihilation of the tungsten-rich conductive channel between two electrodes. Information on the physical and chemical nature of conductive filaments offers insightful design strategies for resistive switching memories with excellent performances. Moreover, we demonstrate the promising applicability of the cathodic electrodeposition method for future resistive ...

The rational design and exploration of electrochromic devices will find a wide range of applications in smart windows for energy-efficient buildings, low-power displays, self-dimming rear mirrors for automobiles, electrochromic e-skins, and so on. Electrochromic devices generally consist of multilayer structures with transparent conductors, electrochromic films, ion conductors, and ion storage films. Synthetic strategies and new materials for electrochromic films and transparent conductors, comprehensive electrochemical kinetic analysis, and novel device design are areas of active study worldwide. These are believed to be the key factors that will help to significantly improve the electrochromic performance and extend their application areas. In this Account, we present our strategies to design and fabricate electrochromic devices with high performance and multifunctionality. We first describe the synthetic strategies, in which a porous tungsten oxide (WO3) film with nearly ideal optical modulation and fast switching was prepared by a pulsed electrochemical deposition method. Multiple strategies, such as sol-gel/inkjet printing methods, hydrothermal/inkjet printing methods, and a novel hybrid transparent conductor/electrochromic layer have been developed to prepare high-performance electrochromic films. We then summarize the recent advances in transparent conductors and ion conductor layers, which play critial roles in electrochromic devices. Benefiting from the developments of soft transparent conductive substrates, highly deformable electrochromic devices that are flexible, foldable, stretchable, and wearable have been achieved. These emerging devices have great potential in applications such as soft displays, electrochromic e-skins, deformable electrochromic films, and so on. We finally present a concept of multifunctional smart glass, which can change its color to dynamically adjust the daylight and solar heat input of the building or protect the users' privacy during the daytime. Energy can also be stored in the smart windows during the daytime simultaneously and be discharged for use in the evening. These results reveal that the electrochromic devices have potential applications in a wide range of areas. We hope that this Account will promote further efforts toward fundamental research on electrochromic materials and the development of new multifunctional electrochromic devices to meet the growing demands for next-generation electronic systems.

Hexagonal boron nitride (hBN), which is a 2D layered dielectric material, sometimes referred as “white graphene” due to its structural similarity with graphene, has attracted much attention due to its fascinating physical properties. Here, for the first time the use of chemical vapor deposition -grown hBN films to fabricate ultrathin (≈3 nm) flexible hBN-based resistive switching memory device is reported, and the switching mechanism through conductive atomic force microscopy and ex situ transmission electron microscopy is studied. The hBN-based resistive memory exhibits reproducible switching endurance, long retention time, and the capability to operate under extreme bending conditions. Contrary to the conventional electrochemical metallization theory, the conductive filament is found to commence its growth from the anode to cathode. This work provides an important step for broadening and deepening the understanding on the switching mechanism in filament-based resistive memories and propels the 2D material application in the resistive memory in future computing systems.

Ultrathin tungsten molybdenum oxide nanoparticle films were fabricated from aqueous ink by a spray coating technique. With the in situ heating of the hot plate during the spray coating process, the detrimental effects of oxygen vacancies on electrochromic (EC) materials could be eliminated. The spray coated ultrathin films exhibit higher contrast than the drop casted films, which would provide a versatile and promising platform for energy-saving smart (ESS) windows, batteries, and other applications.

In this paper, we investigate the (2+1)-dimensional (D) sine-Gordon (SG) equation, to describe the propagation of localized light waves in nonlinear media. The main purpose is to obtain a simple specific form of exact solutions of the (2+1)-D SG equation by Hirota’s bilinear method. The novel dynamical behavior is discussed systematically for some special types of localized excitations, such as multi-dromion, multi-lump, plateau and basin solitons, the quasi-tetragonal breather, and elliptical embedded solitons, which are derived by selecting two arbitrary functions in the solution appropriately. We find that the collision of (2+1)-D solitons could be elastic but also inelastic, depending on the functional form of the solitons.

Some animals and plants in nature are endowed with elegant color-changing ability, which inspired the developments of biomimetic systems with multifunctionality, such as controllable colors, transmittance, and mechanical pliability that are significant for the development of energy-efficient and deformable chromic devices, such as wearable displays, smart windows, decorative architectures, camouflage devices, etc. Inspired by the color-changing ability of diphylleia grayi (commonly known as skeleton flower), we developed a porous PDMS film that dynamically and dramatically changes its color by the adsorption/desorption of minute amount of water (5 g m-2) or other solvents. This hydrochromic phenomenon was analyzed in detail and it matched well with the Mie scattering theory. The porous PDMS film of about 0.4 mm thick exhibits a large optical modulation (about 75~80%) in the broad visible and near infrared region and coloration speed of less than 9 mins. Additionally, the PDMS film can sustain uniaxial strain up to 100% at both transparent and colored states. We believe this new strategy to develop highly scalable porous PDMS film offers a practical route to realize bionic and botanic inspired deformable energy-efficient façade, chromogenic wearables, smart window, smart display, and camouflage etc. NRF (Natl Research Foundation, S’pore) Accepted version

Graphene nanosheet films with improved durability and load capability are highly desired to realize the engineering application of graphene as solid lubricants. Here, we report a general approach to fabricate anchored graphene nanosheet films (A-GNSF), which is based on the selective electrochemical dissolution of graphene-containing metal matrix composites. A-GNSF are composing of many anchored graphene nanosheets, whose parts of basal plane expose on the graphene-containing metal matrix composite's surface while other parts of their basal plane anchor into the composite. The microstructure evolution of the A-GNSF as a function of the duration of selective electrochemical dissolution and the graphene content in composites is investigated and is correlated with their tribological performance. The mechanism on reduction of friction and wear for A-GNSF is also discussed. The results show the unique architecture of the A-GNSF greatly contributes to the rapid formation and the stability of the in-situ developed graphene sliding against graphene lubricating interface. As a consequent, A-GNSF show a friction coefficient as low as 0.14, excellent wear resistance and long lifetime under a contact pressure that is up to 0.88 GPa. Keywords: Graphene, Durability, Load capability, Tribolayer, Transfer layer

Stretchable conductors are vital and indispensable components in soft electronic systems. The development for stretchable conductors has been highly motivated with different approaches established to address the dilemma in the conductivity and stretchability trade-offs to some extent. Here, a new strategy to achieve superelastic conductors with high conductivity and stable electrical performance under stretching is reported. It is demonstrated that by electrically anchoring conductive fillers with eutectic gallium indium particles (EGaInPs), significant improvement in stretchability and durability can be achieved in stretchable conductors. Different from the strategy of modulating the chemical interactions between the conductive fillers and host polymers, the EGaInPs provide dynamic and robust electrical anchors between the conductive fillers. A superelastic conductor which can achieve a high stretchability with 1000% strain at initial conductivity of 8331 S cm-1 and excellent cycling durability with about eight times resistance change (compared to the initial resistance at 0% strain before stretching) after reversibly stretching to 800% strain for 10 000 times is demonstrated. Applications of the superelastic conductor in an interactive soft touch device and a stretchable light-emitting system are also demonstrated, featuring its promising applications in soft robotics or soft and interactive human-machine interfaces. National Research Foundation (NRF) The authors thank Dr. M. Lin, Dr. J. Xiong, Dr. P, Cui, Q. Kai, and X. Chen for their valuable discussions. This work was financially supported by the National Research Foundation Competitive Research Programme (Award No. NRF-CRP-13-2014-02), and the NRF Investigatorship (NRFI) (Award No. NRF-NRFI2016-05).

Extremely stretchable self‐healing strain sensors based on conductive hydrogel are demonstrated by Pooi See Lee and co‐workers in article number 1600190. The strain sensor provides good response, stability, and signal repeatability under various human motion detections.

Electronics with multifunctionalities such as transparency, portability, and flexibility are anticipated for future circuitry development. Flexible memory is one of the indispensable elements in a hybrid electronic integrated circuit as the information storage device. Herein, we demonstrate a transparent, flexible, and transferable hexagonal boron nitride (hBN)-based resistive switching memory with indium tin oxide (ITO) and graphene electrodes on soft polydimethylsiloxane (PDMS) substrate. The ITO/hBN/graphene/PDMS memory device not only exhibits excellent performance in terms of optical transmittance (∼85% in the visible wavelength), ON/OFF ratio (∼480), retention time (∼5 × 104 s) but also shows robust flexibility under bending conditions and stable operation on arbitrary substrates. More importantly, direct observation of indium filaments in an ITO/hBN/graphene device is found via ex situ transmission electron microscopy, which provides critical insight on the complex resistive switching mechanisms.

Many organisms and animals have sensing abilities that are different from those of human beings; for example, snakes have strong smell-, vibration-, touch- and heat-sensing abilities. A nature-mimicking sensing platform capable of sensing multiple stimuli, such as strain, pressure, temperature and other uncorrelated conditions, is highly desirable to broaden the applications of sensors. Here, we construct a semitransparent intelligent skin-like sensing platform based on polyaniline (PANI) nanowire arrays that can act as a bionic component by simultaneously sensing tactile stimuli and detecting colorless, odorless gas. Our multifunctional bionic sensing strategy is remarkably adaptive for versatile applications. The strain-sensing performance is superior to that of most conducting polymer-based sensors reported so far and is comparable to or even better than traditional metal and carbon nanowire/nanotube-based strain sensors. The highest gauge factor demonstrated is 149, making our system a remarkable candidate for strain-sensing applications. The sensor can accurately detect a wide range of human motions. We also demonstrate the simultaneous controlled olfaction ability for the detection of methane with high sensitivity and a fast response time. These results enable the realization of multifunctional and uncorrelated sensing capabilities, which will afford a wide range of applications to augment robotics, treatment, simulated skin, health monitoring and bionic systems. A wearable sensor can track full-range human motion and sniff out toxic gases using polymer nanowires with features similar to snakeskin. The device, which was developed by Pooi See Lee and co-workers at Nanyang Technological University, is based on polyaniline, a conducting polymer with natural flexibility and chemical sensitivity. Polyaniline often becomes unworkably rigid when deposited as a thin film, but the Singapore-based team avoided this issue by growing a vertical forest of polymer nanowires on a thin silicone support. Scanning electron microscopy revealed that when stretched, the nanowires formed scale-like islands and cracks that alter the resistance of the thin film. The researchers demonstrated that these electrical changes were sensitive enough to use for forehead sensors of breathing and eye movement and as a ‘smelling skin’ for detecting methane–an odorless and explosive gas. A semitransparent intelligent skin-like sensor platform based on polyaniline nanowire arrays was constructed, which can act as bionic component by simultaneously sensing tactile stimuli and detecting colorless odorless gas. The highest gauge factor demonstrated is 149, making it a remarkable candidate in strain sensing applications. Simultaneously, we demonstrate the controlled olfaction ability of the sensor with the detection of methane with high sensitivity and fast response time. These results enable the realization of multifunctional and uncorrelated sensing capabilities that will have wide range applications to augment robotics, treatment, simulate skin, health and bionic system.

Reversible electrochemical mirror (REM) device can be electrochemically tuned to exhibit dual transmittance and reflectance modulations in a single device. Conventional REM devices reversibly switched between transparent and mirror states. However, it is of great challenge to maintain the mirror state of the REM devices due to the diffusion of anions into the metallic film at the open-circuit state. In this work, we report a Cu-based REM device which offers reversible switching between transparent, blue and mirror states with judicious selection of electrolyte and controllable electrodeposition. The blue state can be obtained through the formation of copper (I) chloride, CuCl, when copper (II) chloride CuCl2 undergoes electrochemical reduction. The polymer host, PVA (poly(vinyl alcohol)) plays an important role in reducing the surface roughness of the electrodeposited mirror film, improving film uniformity and sustaining the mirror state of the device during the voltage-off state. NRF (Natl Research Foundation, S’pore) Accepted version

Extremely stretchable self‐healing strain sensors based on conductive hydrogels are successfully fabricated. The strain sensor can achieve autonomic self‐heal electrically and mechanically under ambient conditions, and can sustain extreme elastic strain (1000%) with high gauge factor of 1.51. Furthermore, the strain sensors have good response, signal stability, and repeatability under various human motion detections. NRF (Natl Research Foundation, S’pore) Published version

Multifunctional smart windows are successfully fabricated by assembling inkjet printed CeO2/TiO2 and WO3/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) films as the anode and cathode, respectively. Large optical modulation (more than 70% at 633 nm), fast switching (12.7/15.8 s), high coloration efficiency (108.9 cm2 C−1), and excellent bistability are achieved by the assembled smart windows. The multifunctional smart window not only can be used as typical electrochromic window, which can change its color to dynamically control the solar radiation transmittance through windows or protect privacy during the day, but also can be used as energy-storage device simultaneously. The designed smart window releases the stored energy to light the bulbs and power other electronic devices at night while its color gradually reverts to transparent state. Moreover, the level of stored energy can be monitored via the visually detectable reversible color variation of the window. The fascinating multifunctional smart windows exhibit promising features for a wide range of applications in buildings, airplanes, automobiles, etc. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) This research was funded by the NRF Competitive Research Programme NRF-CRP13-2014-02. Part of the work was also supported by the A*Star-MND Green Building Joint Grant 1321760013, and the Campus for Research Excellence and Technological Enterprise (CREATE) that is supported by the National Research Foundation, Prime Minister’s Office, Singapore.

Porous WO3 films with ultra-high transmittance modulation were successfully fabricated on different substrates by a novel, facile and economical pulsed electrochemical deposited method with 1.1 s interval time between each pulse. The near ideal optical modulation (97.7% at 633 nm), fast switching speed (6 and 2.7 s), high coloration efficiency (118.3 cm2 C−1), and excellent cycling stability are achieved by the porous WO3 on ITO-coated glass. The outstanding electrochromic performances of the porous WO3 film were mainly attributed to the porous structure, which facilitates the charge-transfer, promotes the electrolyte infiltration and alleviates the expansion of the WO3 during H+ insertion compared to that of the compact structure. In addition, the relationships between the structural and electrochemical activity of the electrochromic WO3 films were further explored by the scanning electrochemical microscopy. These results testify that the porous structure can promote the infiltration of electrolyte and reduce the diffusion path, which consequently enhance the electrochemical activity. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Fenestration, such as windows, plays a key role in modern architecture as it has enormous impact on the energy efficiency and comfort to the occupants of the building. Herein, current state‐of‐art strategies of nanostructured electrochromic materials, the fabrication of large scale smart windows, rational design of multifunctional smart chromogenic devices, and their performance are highlighted. Moreover, the current challenges from material selection to smart window performance are discussed and feasible solutions are provided. Development of a novel, simple, and economical synthesis of electrochromic materials is the first step in realizing high‐performance smart window. In addition, electrolyte, packaging materials, and judicious design of the fabrication process also play critical roles in the development of multifunctional and energy‐efficient smart windows. Finally, the concept of energy‐efficient multifunctional smart windows is addressed in which the smart windows are powered by sustainable energy in daytime, while the windows dynamically control the solar radiation into the building through transmittance modulation, enabling adjustable occupant's privacy. Sustainable energy can be stored in the smart windows during daytime and can be discharged to power other electronic devices at night. It is envisioned that this review shall promote a rapid development on electrochromic materials and novel multifunctional smart windows. NRF (Natl Research Foundation, S’pore) Accepted version

Few-layered phosphorene is exfoliated through a liquid phase exfoliation in ethanol, acting as an additive to mix with tempo-oxidized cellulose nanofibrils (CNF), forming a transparent, flexible nanogenerator paper. The gas barrier property of CNF protects phosphorene against oxidation in ambient condition. The phosphorene in the hybrid paper is stable over six months even with exposure to ambient condition (23 °C, 70% RH) in air. The hybrid paper is used as an active layer to construct a triboelectric energy nanogenerator (TENG). This hybrid paper shows an open-circuit voltage of 5.2 V with a current density of 1.8 µA cm−2, which is five and nine times higher than that of the pure CNF paper device, respectively. This work reveals the role of phosphorene in acting as a charge carrier in the hybrid paper and demonstrates a new way to attain stable functional phosphorene hybrids in ambient condition. The resultant phosphorene hybrid paper could be used as a building block for TENG with enhanced output performance.

Lithium-ion capacitors (LICs) are promising electrical energy storage systems for mid-to-large-scale applications due to the high energy and large power output without sacrificing long cycle stability. However, due to the different energy storage mechanisms between anode and cathode, the energy densities of LICs often degrade noticeably at high power density, because of the sluggish kinetics limitation at the battery-type anode side. Herein, a high-performance LIC by well-defined ZnMn2 O4 -graphene hybrid nanosheets anode and N-doped carbon nanosheets cathode is presented. The 2D nanomaterials offer high specific surface areas in favor of a fast ion transport and storage with shortened ion diffusion length, enabling fast charge and discharge. The fabricated LIC delivers a high specific energy of 202.8 Wh kg-1 at specific power of 180 W kg-1 , and the specific energy remains 98 Wh kg-1 even when the specific power achieves as high as 21 kW kg-1 . National Research Foundation (NRF) This work was financially supported by the National Research Foundation Competitive Research Programme, Award No. NRF-CRP-13-2014-02, and the NRF Investigatorship (NRFI), Award No. NRF-NRFI2016-05.

Silver grids are attractive for replacing indium tin oxide as flexible transparent conductors. This work aims to improve the electrochemical stability of silver-based transparent conductors. A silver grid/PEDOT:PSS hybrid film with high conductivity and excellent stability is successfully fabricated. Its functionality for flexible electrochromic applications is demonstrated by coating one layer of WO3 nanoparticles on the silver grid/PEDOT:PSS hybrid film. This hybrid structure presents a large optical modulation of 81.9% at 633 nm, fast switching, and high coloration efficiency (124.5 cm2 C−1). More importantly, an excellent electrochemical cycling stability (sustaining 79.1% of their initial transmittance modulation after 1000 cycles) and remarkable mechanical flexibility (optical modulation decay of only 7.5% after 1200 compressive bending cycles) is achieved. A novel smart supercapacitor is presented that functions as a regular energy-storage device and simultaneously monitors the level of stored energy by a rapid and reversible color variation even at high current charge/discharge conditions. The film sustains an optical modulation of 87.7% and a specific capacitance of 67.2% at 10 A g−1 compared to their initial value at a current density of 1 A g−1. The high-performance silver grid/PEDOT:PSS hybrid transparent films exhibit promising features for various emerging flexible electronics and optoelectronic devices. NRF (Natl Research Foundation, S’pore) Accepted version