Integrated GWF/PDMS composite sensors with Bluetooth wireless communication and smartphone function as a wireless wearable musical instrument.

Advanced wearable strain sensors with high sensitivity and stretchability are an essential component of flexible and soft electronic devices. Conventional metal-and semiconductor-based strain sensors are rigid, fragile, and opaque, restricting their applications in wearable electronics. Graphene-based percolative structures possess high flexibility and transparency but lack high sensitivity and stretchability. Inspired by the highly flexible spider web architecture, we propose semitransparent, ultrasensitive, and wearable strain sensors made from an elastomer-filled graphene woven fabric (E-GWF) for monitoring human physiological signals. The highly flexible elastomer microskeleton and the hierarchical structure of a graphene tube offer the strain sensor with both excellent sensing and switching capabilities. Two different types of E-GWF sensors, including freestanding E-GWF and E-GWF/polydimethylsiloxane (PDMS) composites, are developed. When their structure is controlled and optimized, the E-GWF strain sensors simultaneously exhibit extraordinary characteristics, such as a high gauge factor (70 at 10% strain, which ascends to 282 at 20%) in respect to other semitransparent or transparent strain sensors, a broad sensing range up to 30%, and excellent linearity. The E-GWF/PDMS composite sensor shows a unique reversible switching behavior at a high strain level of 30−50%, making it a suitable material for fast and reversible strain switching required in many early warning systems. With a view to real-world applications of these sensors and switches, we demonstrate human motion detection and switch controls of light-emitting-diode lamps and liquid-crystal-display circuits. Their unique structure and capabilities can find a wide range of practical applications, such as health monitoring, medical diagnosis, early warning systems for structural failure, and wearable displays.

The aim of this study is to evaluate the effects of different particle sizes colloidal nanosilica (30, 60, and 140 nm) on the early performance of Portland cement. Flowability, mechanical property, and microstructural characterization tests were conducted to investigate the macroscopic and microscopic properties. The results revealed that the flowability of the paste decreased with the reduction of the particle size of colloidal nanosilica. The main reason was that the sol may form flocculation restricting a part of free water under ion environment, and this phenomenon became more serious as the particle size decreased. The compressive strength with 60-nm sol was higher than that of the other two, and hydration activities under different situations were further proved by hydration heat analysis. The reasons causing this result were mainly because flocculation limited the original chemical activity like pozzolanic and seeding effects of nanomaterials. Through thermogravimetric analysis and X-ray diffraction, it can be concluded that the seeding and pozzolanic effects of nanomaterials dominated the hydration process at different periods. Comparing images from scanning electron microscopy, the microstructure was most compact when incorporated into 60-nm sol, and filling effects also contributed to the performance during hardening.

The [Formula: see text] ([Formula: see text] = 0, 0.025, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, 0.4 and 0.5) nanopowders were synthesized by the hydrothermal method and then were hot-pressed into bulk alloys. The effects of [Formula: see text] secondary phase on the thermoelectric (TE) properties of [Formula: see text] were investigated. For [Formula: see text] and [Formula: see text], both their electrical resistivity and Seebeck coefficients increase. While for [Formula: see text], they decrease instead. The samples for [Formula: see text] have lower thermal conductivity. However, for [Formula: see text], the thermal conductivity rises remarkably. As an overall result, the maximum value of dimensionless TE figure of merit (ZT) reaches 1.52 at 873 K for the sample of [Formula: see text], 36.5% higher than for the sample without [Formula: see text].

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Facing the increasing demand for various renewable energy storage devices and wearable and portable energy storage systems, the research on electrode materials with low costs and high energy densities has attracted great attention. Herein, free-standing rGO-CNT nanocomposites have been successfully synthesized by a facile hydrothermal method, in which the hierarchical porous network nanostructure is synergistically assembled by rGO nanosheets and CNT with interlaced network distribution. The rGO-CNT composite electrodes with synergistic enhancement of rGO and CNT exhibit high specific capacitance, excellent rate capability, exceptional conductivity and outstanding long-term cycling stability, especially for the optimal rGO-CNT30 electrode. Applied to a symmetric supercapacitor systems (SSS) assembled with an rGO-CNT30 electrode and with 1 M Na2SO4 aqueous solution as the electrolyte, the SSS possesses a high energy density of 12.29 W h kg−1 and an outstanding cycling stability, with 91.42% of initial specific capacitance after 18,000 cycles. Results from these electrochemical properties suggest that the rGO-CNT30 nanocomposite electrode is a promising candidate for the development of flexible and lightweight high-performance supercapacitors.

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