Search

The up-to-date progress of the multifunctional MXene hydrogels for flexible wearable electronics is summarized. The critical challenges and prospects are highlighted for the future developments of MXene hydrogel-based wearable electronic devices with high performance and fascinating multifunctionality for versatile applications.

A stiff yet tough healable nanocomposite assembled from supramolecular polymer and MXene nanosheets was reported through molecular design and structural processing, offering an inspiring strategy of richly designed soft polymers in a rigid inorganic framework to integrate desirable attributes.

Flexible, breathable, and degradable pressure sensors with excellent sensing performance are drawing tremendous attention for various practical applications in wearable artificial skins, healthcare monitoring, and artificial intelligence due to their flexibility, breathability, lightweight, decreased electronic rubbish, and environmentally friendly impact. However, traditional plastic or elastomer substrates with impermeability, uncomfortableness, mechanical mismatches, and nondegradability greatly restricted their practical applications. Therefore, the fabrication of such pressure sensors with high flexibility, facile degradability, and breathability is still a critical challenge and highly desired. Herein, we present a wearable, breathable, degradable, and highly sensitive MXene/protein nanocomposites-based pressure sensor. The fabricated MXene/protein-based pressure sensor is assembled from a breathable conductive MXene coated silk fibroin nanofiber (MXene-SF) membrane and a silk fibroin nanofiber membrane patterned with a MXene ink-printed (MXene ink-SF) interdigitated electrode, which can serve as the sensing layer and the electrode layer, respectively. The assembled pressure sensor exhibits a wide sensing range (up to 39.3 kPa), high sensitivity (298.4 kPa-1 for 1.4-15.7 kPa; 171.9 kPa-1 for 15.7-39.3 kPa), fast response/recovery time (7/16 ms), reliable breathability, excellent cycling stability over 10 000 cycles, good biocompatibility, and robust degradability. Furthermore, it shows great sensing performance in monitoring human psychological signals, acting as an artificial skin for the quantitative illustration of pressure distribution, and wireless biomonitoring in real time. Considering the biodegradable and breathable features, the sensor may become promising to find potential applications in smart electronic skins, human motion detection, disease diagnosis, and human-machine interaction.

Portable and wearable dual-mode sensors that can simultaneously detect multiple stimuli are essential for emerging artificial intelligence applications, and most efforts are devoted to exploring pressure-sensing devices. It is still challenging to integrate temperature and pressure-sensing functions into one sensor without the requirement for complex decoupling processes. Herein, we develop a self-powered and multifunctional dual-mode sensor by dip-coating melamine sponge with both poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and carboxylated single-walled carbon nanotubes (CNTs). By integrating thermoelectric and conductive PEDOT:PSS/CNT components with the hydrophilic and resilient porous sponge, the resultant sensor is efficient in independently detecting temperature and pressure changes. The temperature and pressure stimuli can be independently converted to voltage and electrical resistance signals on the basis of the Seebeck and piezoresistive effects, respectively. The sensor exhibits a high Seebeck coefficient of 35.9 μV K

Over the past few years, wearable electronics and smart textiles have seen tremendous growth in both academia and industries. However, it is still a challenge to prepare robust, flexible, wearable, and multiresponsive textile electronics. A newly blooming two-dimensional (2D) transition-metal carbide/nitride (MXene) is regarded as an ideal active material to build multifunctional electronics due to its intriguing properties. Herein, a hydrophobic and multifunctional textile composite (Si-MAP) was prepared by decoration of conductive MXene nanosheets onto air-laid paper, followed by wrapping with poly(dimethylsiloxane) (PDMS). These obtained smart textiles exhibited excellent electronic/photonic/mechanical triresponsive properties: Si-MAPs could reach high equilibrium temperatures (104.9 and 118.7 °C) under quite low power illumination (1.25 W cm-2) and working voltage (4 V). The Si-MAP pressure sensor exhibited high sensitivity and rapid response time (30-40 ms), which can capture a wide range of human movements. Moreover, the thin PDMS layer not only rendered the textile composites hydrophobic but also improved the stability and adaptation for daily use. Remarkably, the hydrophobic Si-MAPs have maintained the advantages of breathability and washability, which make them suitable for wearing. Thus, this smart Si-MAP textile provides a reference for the study of the next generation of light, portable, and wearable textile-based electronic devices.

To further explore the research of financial time series prediction and broaden the application scope of Gaussian distribution probability density equation, based on the nonlinear differential equation of Gaussian distribution probability density, the semi-supervised Gaussian process model is taken as the research object to discuss the application of semi-supervised Gaussian process model in the stock market. Shanghai 180 Index, Shanghai (Securities) Composite Index and the yield of three stocks are studied in detail. The specific results are as follows. The prediction accuracy of Shanghai 180 Index is 83%, and the prediction accuracy of Shanghai (Securities) Composite Index is 78%. The stock yield series curves of the three stocks have the characteristics of peak and thick tail, which do not obey the normal distribution. Among the three models of semi-supervised Gaussian process model, initial Gaussian process model and SVM algorithm model, the prediction accuracy of semi-supervised Gaussian process model is the best, and the prediction accuracy of the yield of three stocks is 82.45%, 85.03% and 84.53%, respectively. The research results can fully prove that the semi-supervised Gaussian process model has good application effect in stock time series prediction. The research content can provide scientific and sufficient reference for the follow-up research of financial time series, and also has important significance for the research of Gaussian process model.

The purposes of this paper are to improve the scientific processing level of risk management in the financial field, enrich the application range of mathematical models in financial calculations, and comprehensively discuss the theories and concepts of mathematical finance and stochastic differential equations. More importantly, the common option pricing issues in financial risk management have been researched using the forward–backward stochastic differential equation. The fully discrete and uncoupled forward–backward stochastic differential equation is employed to analyze the spread option and the better-of option, the complicated multi-asset options. Results demonstrate that the fully discrete and uncoupled forward–backward stochastic differential equations can effectively price the spread option and the better-of option. Simulation by the MATLAB software suggests that the value of spread option pricing is 0.0264, and the value of the better-of option pricing is 0.0251. The above results can provide scientific and useful references for the subsequent application research on forward–backward stochastic differential equations in the financial field; simultaneously, they also have important practical significance for researching on and developing the financial risk management.

Flexible wearable conductive hydrogel-based epidermal sensors have attracted tremendous attention due to their versatile potential applications in soft robotics, personal healthcare monitoring and electronic skins. However, it remains a critical challenge for hydrogel-based epidermal sensors to simultaneously achieve self-healing capability, self-adhesiveness and long-lasting moisture retention for full-scale human motion biomonitoring. Herein, a conductive, self-healing, adhesive and long-lastingly moist MXene nanocomposite organohydrogel is prepared from the conformal coating of the MXene nanosheet network by the polymer networks of dopamine grafted sodium alginate (Alg-DA), phenylboronic acid grafted sodium alginate (Alg-PBA) and polyacrylamide (PAAm) with a glycerol/water binary solvent as the dispersion medium. The obtained MXene nanocomposite organohydrogel exhibits excellent self-healing capability, superior self-adhesive performance and long-lasting moisture retention (10 days). Furthermore, the MXene nanocomposite organohydrogel can be assembled as a wearable epidermal sensor to detect human motion including large deformation (finger bending and wrist bending) and tiny deformation (swallowing, breathing, and pulse) with durable stability. Meanwhile, the assembled epidermal sensor could be employed to monitor human activities wirelessly via connecting a wireless transmitter. This work sheds new light on the development of flexible, self-healing, adhesive and long-lastingly moist epidermal sensors and electronic skins for personalized healthcare monitoring, human–machine interfaces, and artificial intelligence.

Wearable epidermal sensors are attracting growing interests in human activity monitoring and flexible touch display, but they are still limited by the poor self-healing property and the difficult dissolvable feature. Herein, we report polyvinyl alcohol (PVA)-stabilized liquid metal particles (LMPs) (PVA-LMPs) hydrogels with excellent self-healing performance and the dissolvable feature for wearable epidermal sensors, constructed by dispersing LMPs of eutectic gallium and indium into the borate-modified PVA polymer networks. Interestingly, the PVA-LMPs hydrogels exhibited excellent electrically and mechanically self-healing ability. Moreover, the PVA-LMPs hydrogel can be fabricated as epidermal sensors, which can accurately monitor the human activities. Additionally, the epidermal sensors are dissolvable, showing an attractive feature for on demand transient electronics. It is demonstrated that the hydroxyl groups of PVA can stabilize LMPs via hydrogen-bonding interactions. Furthermore, the dynamic cross-linking bonds between hydrogels and LMPs can rupture and coalesce reversibly in the hydrogel network, which endow the hydrogels with both electrically and mechanically self-healing ability. This work shows the potential of constructing next-generation multifunctional hydrogel-based epidermal sensors for human activity monitoring, wearable healthcare diagnosis, portable electronics, and robot tactile systems.

Flexible, breathable, and degradable pressure sensors with excellent sensing performance are drawing tremendous attention for various practical applications in wearable artificial skins, healthcare monitoring, and artificial intelligence due to their flexibility, breathability, lightweight, decreased electronic rubbish, and environmentally friendly impact. However, traditional plastic or elastomer substrates with impermeability, uncomfortableness, mechanical mismatches, and nondegradability greatly restricted their practical applications. Therefore, the fabrication of such pressure sensors with high flexibility, facile degradability, and breathability is still a critical challenge and highly desired. Herein, we present a wearable, breathable, degradable, and highly sensitive MXene/protein nanocomposites-based pressure sensor. The fabricated MXene/protein-based pressure sensor is assembled from a breathable conductive MXene coated silk fibroin nanofiber (MXene-SF) membrane and a silk fibroin nanofiber membrane patterned with a MXene ink-printed (MXene ink-SF) interdigitated electrode, which can serve as the sensing layer and the electrode layer, respectively. The assembled pressure sensor exhibits a wide sensing range (up to 39.3 kPa), high sensitivity (298.4 kPa

Conductive hydrogels have emerged as promising material candidates for epidermal sensors due to their similarity to biological tissues, good wearability, and high accuracy of information acquisition. However, it is difficult to simultaneously achieve conductive hydrogel-based epidermal sensors with reliable healability for long-term usage, robust mechanical property, environmental degradability for decreased electronic waste, and sensing capability of the physiological stimuli and the electrophysiological signals. Herein, we propose the synthesis strategy of a multifunctional epidermal sensor based on the highly stretchable, self-healing, degradable, and biocompatible nanocomposite hydrogel, which is fabricated from the conformal coating of a MXene (Ti3C2Tx) network by the hydrogel polymer networks involving poly(acrylic acid) and amorphous calcium carbonate. The epidermal sensor can be employed to sensitively detect human motions with the fast response time (20 ms) and to serve as electronic skins for wirelessly monitoring the electrophysiological signals (such as the electromyogram and electrocardiogram signals). Meanwhile, the multifunctional epidermal sensor could be degraded in phosphate buffered saline solution, which could not cause any pollution to the environment. This line of research work sheds light on the fabrication of the healable, degradable, and electrophysiological signal-sensitive conductive hydrogel-based epidermal sensors with potential applications in human-machine interactions, healthy diagnosis, and smart robot prosthesis devices.

Over the past few years, wearable electronics and smart textiles have seen tremendous growth in both academia and industries. However, it is still a challenge to prepare robust, flexible, wearable, and multiresponsive textile electronics. A newly blooming two-dimensional (2D) transition-metal carbide/nitride (MXene) is regarded as an ideal active material to build multifunctional electronics due to its intriguing properties. Herein, a hydrophobic and multifunctional textile composite (Si-MAP) was prepared by decoration of conductive MXene nanosheets onto air-laid paper, followed by wrapping with poly(dimethylsiloxane) (PDMS). These obtained smart textiles exhibited excellent electronic/photonic/mechanical triresponsive properties: Si-MAPs could reach high equilibrium temperatures (104.9 and 118.7 °C) under quite low power illumination (1.25 W cm

In recent decades, cellulose has been extensively investigated due to its favourable properties, such as hydrophilicity, low-cost, biodegradability, biocompatibility, and non-toxicity, which makes it a good feedstock for the synthesis of biocompatible hydrogels. The plentiful hydrophilic functional groups (such as hydroxyl, carboxyl, and aldehyde groups) in the backbone of cellulose and its derivatives can be used to prepare hydrogels easily with fascinating structures and properties, leading to burgeoning research interest in biomedical applications. This review focuses on state-of-the-art progress in cellulose-based hydrogels, which covers from their preparation methods (including chemical methods and physical methods) and physicochemical properties (such as stimuli-responsive properties, mechanical properties, and self-healing properties) to their biomedical applications, including drug delivery, tissue engineering, wound dressing, bioimaging, wearable sensors and so on. Moreover, the current challenges and future prospects for cellulose-based hydrogels in regard to their biomedical applications are also discussed at the end.

The remarkable progress in efforts to prepare conductive self-healing hydrogels mimicking human skin’s functions has been witnessed in recent years. However, it remains a great challenge to develop an integrated conductive gel combining excellent self-healing and mechanical properties, which is derived from their inherent compromise between the dynamic cross-links for healing and steady cross-links for mechanical strength. In this work, we design a tough, self-healing, and self-adhesive ionic gel by constructing synergistic multiple coordination bonds among tannic acid-coated cellulose nanocrystals (TA@CNCs), poly(acrylic acid) chains, and metal ions in a covalent polymer network. The incorporated TA@CNC acts as a dynamic connected bridge in the hierarchically porous network mediated by multiple coordination bonds, endowing the ionic gels the superior mechanical performance. Reversible nature of dynamic coordination interactions leads to excellent recovery property as well as reliable mechanical and elect...

Real-time ammonia (NH3) detection in anaerobic digestion is highly desirable, due to the ammonia inhibition on methane production. Here, the interconnected nanocomposite network of polyaniline (PANI) nanoparticle-coated carbon nanotube (CNT) and PANI nanofiber is fabricated by adding ammonium persulfate into CNT-containing aniline solution for PANI polymerization and film deposition. The film is assembled as high-sensitive ammonia sensors, exhibiting highly sensitive NH3 sensing from 200 ppb to 50 ppm, fast response/recovery time, room-temperature operation without external aid, reliable flexibility and excellent selectivity to NH3 compared to other volatile organic compounds.

BACKGROUND Osteogenic differentiation of periodontal ligament stem cells (PDLSCs) is associated with periodontitis. It has been reported that long noncoding RNA X-inactive specific transcript (lncRNA XIST) is upregulated and microRNA-214-3p (miR-214-3p) is downregulated in PDLSCs after osteogenic induction. However, whether XIST is involved in osteogenic differentiation of PDLSCs via miR-214-3p has not been reported. MATERIAL AND METHODS The protein expressions of osteogenic markers alkaline phosphatase (ALP), osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2) were examined by Western blot. The levels of miR-214-3p and XIST were determined by qRT-PCR. The relationship between miR-214-3p and XIST was evaluated by luciferase reporter, RNA immunoprecipitation, and RNA pulldown assays. RESULTS We found that XIST was increased and miR-214-3p was decreased in PDLSCs after osteogenic stimulation. Silencing of XIST decreased the protein expressions of ALP, OCN, and RUNX2, and also decreased ALP activity. Higher miR-214-3p levels also inhibited osteogenic differentiation of PDLSCs. XIST interacted with miR-214-3p and depletion of miR-214-3p mitigated XIST absence-mediated suppression of osteogenic differentiation. CONCLUSIONS XIST participates in osteogenic differentiation of PDLSCs by sponging miR-214-3p.

We investigated the therapeutic effects of microRNA-139-5p in relation to osteoporosis of bone marrow-derived mesenchymal stem cell (BMSCs) and its underlying mechanisms. In this study we used a dexamethasone-induced in vivo model of osteoporosis and BMSCs were used for the in vitro model. Real-time quantitative polymerase chain reaction (RT-PCR) and gene chip were used to analyze the expression of microRNA-139-5p. In an osteoporosis rat model, the expression of microRNA-139-5p was increased, compared with normal group. Downregulation of microRNA-139-5p promotes cell proliferation and osteogenic differentiation in BMSCs. Especially, up-regulation of microRNA-139-5p reduced cell proliferation and osteogenic differentiation in BMSCs. Overexpression of miR-139-5p induced Wnt/β-catenin and down-regulated NOTCH1 signaling in BMSCs. Down-regulation of miR-139-5p suppressed Wnt/β-catenin and induced NOTCH1 signaling in BMSCs. The inhibition of NOTCH1 reduced the effects of anti-miR-139-5p on cell proliferation and osteogenic differentiation in BMSCs. Activation of Wnt/β-catenin also inhibited the effects of anti-miR-139-5p on cell proliferation and osteogenic differentiation in BMSCs. Taken together, our results suggested that the inhibition of microRNA-139-5p promotes osteogenic differentiation of BMSCs via targeting Wnt/β-catenin signaling pathway by NOTCH1.

Flexible wearable soft epidermal sensors assembled from conductive hydrogels have recently attracted tremendous research attention because of their extensive and significant applications in body-attachable healthcare monitoring, ultrasensitive electronic skins, and personal healthcare diagnosis. However, traditional conductive hydrogels inevitably face the challenge of long-term usage under room temperature and cold conditions, due to the lost water, elasticity, and conductivity at room temperature, and freezing at the water icing temperatures. It severely limits the applications in flexible electronics at room temperature or cold environment. Herein, we report a flexible, wearable, antifreezing, and healable epidermal sensor assembled from an antifreezing, long-lasting moist, and conductive organohydrogel. The nanocomposite organohydrogel is prepared from the conformal coating of functionalized reduced graphene oxide network by the hydrogel polymer networks consisting of poly(vinyl alcohol), phenylboronic acid grafted alginate, and polyacrylamide in the binary ethylene glycol (EG)/H

Anisotropic composite films of polyaniline (PANI) with single-walled carbon nanotube (SWCNT) were prepared by in situ electropolymerization on highly oriented high-density polyethylene (HDPE) films. Polarized UV-vis and Raman spectra confirm the anisotropic arrangement of PANI molecular chains in the composite films. The conductivities of 16.6 ± 0.2 and 2.07 ± 0.2 S cm

2D transition-metal carbides and nitrides, named MXenes, are promising materials for energy storage, but suffer from aggregation and restacking of the 2D nanosheets, which limits their electrochemical performance. In order to overcome this problem and realize the full potential of MXene nanosheets, a 3D MXene foam with developed porous structure is established via a simple sulfur-template method, which is freestanding, flexible, and highly conductive, and can be directly used as the electrode in lithium-ion batteries. The 3D porous architecture of the MXene foam offers massive active sites to enhance the lithium storage capacity. Moreover, its foam structure facilitates electrolyte infiltration for fast Li+ transfer. As a result, this flexible 3D porous MXene foam exhibits significantly enhanced capacity of 455.5 mAh g-1 at 50 mA g-1 , excellent rate performance (101 mAh g-1 at 18 A g-1 ), and superior ultralong-term cycle stability (220 mAh g-1 at 1 A g-1 after 3500 cycles). This work not only demonstrates the great superiority of the 3D porous MXene foam but also proposes the sulfur-template method for controllable constructing of the 3D foam from 2D nanosheets at a relatively low temperature.

Highlights An ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure was successfully fabricated via a facile alternating vacuum-assisted filtration process.The composite paper exhibits excellent mechanical property and electromagnetic interference shielding performance. Electronic supplementary material The online version of this article (10.1007/s40820-019-0304-y) contains supplementary material, which is available to authorized users., As the rapid development of portable and wearable devices, different electromagnetic interference (EMI) shielding materials with high efficiency have been desired to eliminate the resulting radiation pollution. However, limited EMI shielding materials are successfully used in practical applications, due to the heavy thickness and absence of sufficient strength or flexibility. Herein, an ultrathin and flexible carbon nanotubes/MXene/cellulose nanofibrils composite paper with gradient and sandwich structure is constructed for EMI shielding application via a facile alternating vacuum-assisted filtration process. The composite paper exhibits outstanding mechanical properties with a tensile strength of 97.9 ± 5.0 MPa and a fracture strain of 4.6 ± 0.2%. Particularly, the paper shows a high electrical conductivity of 2506.6 S m−1 and EMI shielding effectiveness (EMI SE) of 38.4 dB due to the sandwich structure in improving EMI SE, and the gradient structure on regulating the contributions from reflection and absorption. This strategy is of great significance in fabricating ultrathin and flexible composite paper for highly efficient EMI shielding performance and in broadening the practical applications of MXene-based composite materials. Electronic supplementary material The online version of this article (10.1007/s40820-019-0304-y) contains supplementary material, which is available to authorized users.

A flexible, transparent, and portable wrist strap sensor device has been well developed from a hierarchical polydiacetylene/MoS2 nanocomposite (PDA/MoS2) film. MoS2 with a nanoflake structure and chelation ability acts as a supporter for PDA films to enhance the porosity as well as the transparency of films, which increases the sensitivity, selectivity, and application potential of a PDA sensor. The PDA/MoS2 film sensor shows a linear detection range for N,N-dimethylformamide (DMF) vapor from 0.01% to 4% with a visible blue to red color change detected by the naked eye, which is more sensitive than other organic vapors. Exploiting the high transparency, vivid color change, remarkable flexibility and reliability, a wearable wrist strap sensor device with visible DMF sensing ability is fabricated based on PDA/MoS2 films, indicating their great potential for smart wearable devices.

Hybrid supercapacitors (HSCs), which usually involve faradaic or pseudocapacitive positive materials and electric double-layer capacitive negative materials, have demonstrated great potentials with enhanced energy density outdistancing traditional electrical double-layer capacitors. To endow materials with higher energy density and power density, the rational design and synthesis of electrodes with hierarchical and mesoporous structure are highly desired. In this work, we report the fabrication of hierarchical mesoporous NiO nanoarrays (NiO-HMNAs) as a battery-type electrode for hybrid supercapacitor with an ultrahigh specific capacitance (3114 F g −1 at the current density of 5 mA cm −2 ), which is beyond the theoretical faradaic capacitance value of NiO. NiO-HMNAs were prepared by a self-generated sacrificial template approach, which involves the preparation of hierarchical ZnO/NiO composites by co-deposition of Zn 2+ and Ni 2+ and the removal of ZnO by an alkali etching process to construct mesoporous structure. The ultrahigh capacitance of NiO-HMNAs is ascribed to the nearly full redox reaction of NiO in the unique hierarchical mesoporous architecture, and the raised electrical double-layer capacitance at the enlarged surface of nanoarrays. Moreover, the optimized HSC fabricated by using NiO-HMNAs as the positive electrode and macroporous graphene monoliths (MGMs) as the negative electrode has demonstrated a high energy density of 67.0 W h kg −1 at a power density of 320 W kg −1 with a maximum voltage of 1.6 V and outstanding cycleability (capacitance retention of 89.6% after 6000 cycles).

A ‘green’ paper-based flexible room-temperature electronic sensor is assembled from environmentally friendly 3D porous cellulose papers with the filtration coating of hierarchical polyaniline/reduced graphene oxide (PANI/RGO) nanocomposite network, which is prepared by in situ PANI polymerization in RGO solution. The environmentally friendly paper with flexibility, porous structure, portability, and recyclability, is considered as potential substrates for the flexible electronic sensors. The as-assembled flexible electronic gas sensor reveals excellent sensing performance and reliable flexibility without obvious performance change after 1000 bending/extending cycles. The high gas sensing performance could be attributed to synergistic advantages of RGO and PANI, high specific surface area (48.532 m2/g) for efficient adsorption/desorption of vapor analytes, the interconnected nanocomposite sensing network, and the effectively exposed active surfaces. It is anticipated to be extended for fabricating flexible sensors, providing high sensing performance, superior recyclability, robust flexibility and reliable portability to be potentially integrated into handheld flexible electronics.

Mass production of high-quality silver nanowires (Ag NWs) is of significant importance because of its potential applications in flexible transparent conductive devices. Halogen ions have been widely used for the synthesis of Ag NWs; however, owing to the lack of a deep insight into heterogeneous nucleation processes, usually a trace feeding amount (e.g. [Cl–] < 0.25 mM) is used, which in turn lowers the concentration of precursor ([Ag+]). Here we systematically investigated the nucleation and growth behavior of Ag NWs and concluded that the number of heterogeneous nucleation sites was determined by the total surface area of AgCl seeds, which indicated a linear relationship between the concentrations of Ag+ and Cl– during precipitation. Based on this mechanism, we successfully produced high-quality Ag NWs with Ag+ concentrations which were 20 times higher for a polyol system and 5 times higher for an aqueous system as compared to that in the previously reported strategies. Besides, by tailoring the heterogeneous nucleation sites by controlling the size of the AgCl seeds, the diameters of the final Ag NWs could be well controlled even at high Ag+ concentration. Based on the mechanistic understandings, this synthetic strategy could be extended to other AgX-seeds (X = Br–, I– and SO 4 2– ) and the basic principles can be applied to help rational synthesis of other high-yield metal NWs with tunable sizes.

Flexible wearable strain sensors with high sensitivity, broad sensing range, large stretchability and low strain detectability have drawn tremendous interest for various applications in electronic skins, human motion detection, and medical diagnosis. However, conventional strain sensors usually showed narrow sensing range, low sensitivity, and complicated fabrication process, which restrict their potential applications in precise detection of vital healthcare signals. In this work, we report the fabrication of a flexible wearable strain sensor by using the MXene/polyaniline fiber (PANIF) (MXene/PANIF) nanocomposites sensing layer with tile-like stacked hierarchical microstructures, inspired from the overlapped rooftop tiles of the ancient palace. The MXene/PANIF nanocomposites sensing layer with tile-like stacked hierarchical microstructures is prepared via spreading MXene and PANIF layer on the elastic rubber substrate respectively. The assembled strain sensor can be used to detect broad-range (up to 80% strain) human motion with ultralow detection limit (0.1538% strain), high sensitivity (up to 2369.1 for the gauge factor (GF)), and excellent reproducibility and stability. Furthermore, the strain sensor could be coupled to a wireless transmitter for wirelessly human motion monitoring. Therefore, the wearable MXene nanocomposites-based strain sensor is a promising and attractive future electronic device for various real-time human motion detection, personal healthcare monitoring, and clinical diagnosis.