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.
Keywords: graphene woven fabric; spider web; strain sensor; stretchable; transparent.