Muqiang Jian

Carbonized Silk Fabric for Ultrastretchable, Highly Sensitive, and Wearable Strain Sensors

A carbonized plain-weave silk fabric is fabricated into wearable and robust strain sensors, which can be stretched up to 500% and show high sensitivity in a wide strain range. This sensor can be assembled into wearable devices for detection of both large and subtle human activities, showing great potential for monitoring human motions and personal health.

Sheath–Core Graphite/Silk Fiber Made by Dry-Meyer-Rod-Coating for Wearable Strain Sensors

Recent years have witnessed the explosive development of flexible strain sensors. Nanomaterials have been widely utilized to fabricate flexible strain sensors, because of their high flexibility and electrical conductivity. However, the fabrication processes for nanomaterials and the subsequent strain sensors are generally complicated and are manufactured at high cost. In this work, we developed a facile dry-Meyer-rod-coating process to fabricate sheath-core-structured single-fiber strain sensors using ultrafine graphite flakes as the sheath and silk fibers as the core by virtue of their flexibility, high production, and low cost. The fabricated strain sensor exhibits a high sensitivity with a gauge factor of 14.5 within wide workable strain range up to 15%, and outstanding stability (up to 3000 cycles). The single-fiber-based strain sensors could be attached to a human body to detect joint motions or easily integrated into the multidirectional strain sensor for monitoring multiaxial strain, showing great potential applications as wearable strain sensors.

Silk nanofibers as high efficient and lightweight air filter

Silk is a widely available, edible, biocompatible, and environmentally sustainable natural material. Particulate matter (PM) pollution has drawn considerable attention because it is a serious threat to public health. Herein, we report a human-friendly silk nanofiber air filter, which exhibits superior filtration efficiency for both PM2.5 and submicron particles with obviously low pressure drop and low basis weight compared to typical commercial microfiber air filters. Additionally, other functions such as antibacterial activity could be easily integrated into the silk nanofiber air filters, enabling the fabrication of multifunctional air filters. All the above characteristics, combined with the natural abundance and biocompatibility of silk, suggest a great potential for the use of silk nanofibers as air filters, especially as comfortable and personal air purifiers.

Carbonized silk georgette as an ultrasensitive wearable strain sensor for full-range human activity monitoring

The increasing demand of wearable electronic devices has promoted the development of high-performance flexible strain sensors which could monitor various physiological parameters. In this work, using silk georgette, which is a commercially available gauzy and lightweight fabric composed of highly twisted yarns in both warp and weft directions as the raw material, an ultrasensitive strain sensor with a wide workable strain range is fabricated through a facile and large-scale process. The obtained strain sensors exhibit remarkable combined features of ultrahigh sensitivity in a wide sensing range (average gauge factor of 29.7 within 40% strain and of 173.0 for a strain of 60–100%), ultralow detection limit (0.01% strain), high durability and stability (10 000 stretching cycles at 100% strain), fast response (<70 ms) and translucence, which could be ascribed to the unique woven structure of silk georgette. Furthermore, the dependence of the performance of the strain sensors on the woven structures has been demonstrated. Finally, the strain sensors based on silk georgette are demonstrated to show potential for applications in monitoring full-range human activities including both vigorous motions and subtle motions.

Extremely Black Vertically Aligned Carbon Nanotube Arrays for Solar Steam Generation

The unique structure of a vertically aligned carbon nanotube (VACNT) array makes it behave most similarly to a blackbody. It is reported that the optical absorptivity of an extremely black VACNT array is about 0.98-0.99 over a large spectral range of 200 nm-200 μm, inspiring us to explore the performance of VACNT arrays in solar energy harvesting. In this work, we report the highly efficient steam generation simply by laminating a layer of VACNT array on the surface of water to harvest solar energy. It is found that under solar illumination the temperature of upper water can significantly increase with obvious water steam generated, indicating the efficient solar energy harvesting and local temperature rise by the thin layer of VACNTs. We found that the evaporation rate of water assisted by VACNT arrays is 10 times that of bare water, which is the highest ratio for solar-thermal-steam generation ever reported. Remarkably, the solar thermal conversion efficiency reached 90%. The excellent performance could be ascribed to the strong optical absorption and local temperature rise induced by the VACNT layer, as well as the ultrafast water transport through the VACNT layer due to the frictionless wall of CNTs. Based on the above, we further demonstrated the application of VACNT arrays in solar-driven desalination.

Epidermis Microstructure Inspired Graphene Pressure Sensor with Random Distributed Spinosum for High Sensitivity and Large Linearity

Recently, wearable pressure sensors have attracted tremendous attention because of their potential applications in monitoring physiological signals for human healthcare. Sensitivity and linearity are the two most essential parameters for pressure sensors. Although various designed micro/nanostructure morphologies have been introduced, the trade-off between sensitivity and linearity has not been well balanced. Human skin, which contains force receptors in a reticular layer, has a high sensitivity even for large external stimuli. Herein, inspired by the skin epidermis with high-performance force sensing, we have proposed a special surface morphology with spinosum microstructure of random distribution via the combination of an abrasive paper template and reduced graphene oxide. The sensitivity of the graphene pressure sensor with random distribution spinosum (RDS) microstructure is as high as 25.1 kPa-1 in a wide linearity range of 0-2.6 kPa. Our pressure sensor exhibits superior comprehensive properties compared with previous surface-modified pressure sensors. According to simulation and mechanism analyses, the spinosum microstructure and random distribution contribute to the high sensitivity and large linearity range, respectively. In addition, the pressure sensor shows promising potential in detecting human physiological signals, such as heartbeat, respiration, phonation, and human motions of a pushup, arm bending, and walking. The wearable pressure sensor array was further used to detect gait states of supination, neutral, and pronation. The RDS microstructure provides an alternative strategy to improve the performance of pressure sensors and extend their potential applications in monitoring human activities.

An All-Silk-Derived Dual-Mode E-skin for Simultaneous Temperature–Pressure Detection

Flexible skin-mimicking electronics are highly desired for development of smart human-machine interfaces and wearable human-health monitors. Human skins are able to simultaneously detect different information, such as touch, friction, temperature, and humidity. However, due to the mutual interferences of sensors with different functions, it is still a big challenge to fabricate multifunctional electronic skins (E-skins). Herein, a combo temperature-pressure E-skin is reported through assembling a temperature sensor and a strain sensor in both of which flexible and transparent silk-nanofiber-derived carbon fiber membranes (SilkCFM) are used as the active material. The temperature sensor presents high temperature sensitivity of 0.81% per centigrade. The strain sensor shows an extremely high sensitivity with a gauge factor of ∼8350 at 50% strain, enabling the detection of subtle pressure stimuli that induce local strain. Importantly, the structure of the SilkCFM in each sensor is designed to be passive to other stimuli, enabling the integrated E-skin to precisely detect temperature and pressure at the same time. It is demonstrated that the E-skin can detect and distinguish exhaling, finger pressing, and spatial distribution of temperature and pressure, which cannot be realized using single mode sensors. The remarkable performance of the silk-based combo temperature-pressure sensor, together with its green and large-scalable fabrication process, promising its applications in human-machine interfaces and soft electronics.

CVD growth of fingerprint-like patterned 3D graphene film for an ultrasensitive pressure sensor

With the rapid development of wearable devices, flexible pressure sensors with high sensitivity and wide workable range are highly desired. In nature, there are many well-adapted structures developed through natural selection, which inspired us for the design of biomimetic materials or devices. Particularly, human fingertip skin, where many epidermal ridges amplify external stimulations, might be a good example to imitate for highly sensitive sensors. In this work, based on unique chemical vapor depositions (CVD)-grown 3D graphene films that mimic the morphology of fingertip skin, we fabricated flexible pressure sensing membranes, which simultaneously showed a high sensitivity of 110 (kPa)−1 for 0–0.2 kPa and wide workable pressure range (up to 75 kPa). Hierarchical structured PDMS films molded from natural leaves were used as the supporting elastic films for the graphene films, which also contribute to the superior performance of the pressure sensors. The pressure sensor showed a low detection limit (0.2 Pa), fast response (< 30 ms), and excellent stability for more than 10,000 loading/unloading cycles. Based on these features, we demonstrated its applications in detecting tiny objects, sound, and human physiological signals, showing its potential in wearable electronics for health monitoring and human/machine interfaces.

Mineral-Templated 3D Graphene Architectures for Energy-Efficient Electrodes

3D graphene networks have shown extraordinary promise for high-performance electrochemical devices. Herein, the chemical vapor deposition synthesis of a highly porous 3D graphene foam (3D-GF) using naturally abundant calcined Iceland crystal as the template is reported. Intriguingly, the Iceland crystal transforms to CaO monolith with evenly distributed micro/meso/macropores through the releasing of CO2 at high temperature. Meanwhile, the hierarchical structure of the calcined template could be easily tuned under different calcination conditions. By precisely inheriting fine structure from the templates, the as-prepared 3D-GF possesses a tunable hierarchical porosity and low density. Thus, the hierarchical pores offer space for guest hybridization and provide an efficient pathway for ion/charge transport in typical energy conversion/storage systems. The 3D-GF skeleton electrode hybridized with Ni(OH)2 /Co(OH)2 through an optimal electrodeposition condition exhibits a high specific capacitance of 2922.2 F g-1 at a scan rate of 10 mV s-1 , and 2138.4 F g-1 at a discharge current density of 3.1 A g-1 . The hybrid 3D-GF symmetry supercapacitor shows a high energy density of 83.0 Wh kg-1 at a power density of 1011.3 W kg-1 and 31.4 Wh kg-1 at a high power density of 18 845.2 W kg-1 . The facile fabrication process enables the mass production of hierarchical porous 3D-GF for high-performance supercapacitors.

Superelastic wire-shaped supercapacitor sustaining 850% tensile strain based on carbon nanotube@graphene fiber

Stretchable and flexible supercapacitors are highly desired due to their many potential applications in wearable devices. However, it is challenging to fabricate supercapacitors that can withstand large tensile strain while maintaining high performance. Herein, we report an ultra-stretchable wire-shaped supercapacitor based on carbon nanotube@graphene@MnO2 fibers wound around a superelastic core fiber. The supercapacitor can sustain tensile strain up to 850%, which is the highest value reported for this type of device to date, while maintaining stable electrochemical performance. The energy density of the supercapacitor is 3.37 mWh·cm–3 at a power density of 54.0 mW·cm–3. The results show that 82% of the specific capacitance is retained after 1,000 stretch–release cycles with strains of 700%, demonstrating the superior durability of the elastic supercapacitor and showcasing its potential application in ultra-stretchable flexible electronics.