Bioinspired, Self-Powered, and Highly Sensitive Electronic Skin for Sensing Static and Dynamic Pressures.

Flexible piezoresistive pressure sensors obtain global research interest owing to their potential applications in healthcare, human-robot interaction, and artificial nerves. However, an additional power supply is usually required to drive the sensors, which results in increased complexity of the pressure sensing system. Despite the great efforts in pursuing self-powered pressure sensors, most of the self-powered devices can merely detect the dynamic pressure and the reliable static pressure detection is still challenging. With the help of redox-induced electricity, a bioinspired graphite/polydimethylsiloxane piezoresistive composite film acting both as the cathode and pressure sensing layer, a neoteric electronic skin sensor is presented here to detect not only the dynamic forces but also the static forces without an external power supply. Additionally, the sensor exhibits a fascinating pressure sensitivity of ∼103 kPa-1 over a broad sensing range from 0.02 to 30 kPa. Benefiting from the advanced performance of the device, various potential applications including arterial pulse monitoring, human motion detecting, and Morse code generation are successfully demonstrated. This new strategy could pave a way for the development of next-generation self-powered wearable devices.

Highly Sensitive and Ultrastable Skin Sensors for Biopressure and Bioforce Measurements Based on Hierarchical Microstructures.

Piezoresistive microsensors are considered to be essential components of the future wearable electronic devices. However, the expensive cost, complex fabrication technology, poor stability, and low yield have limited their developments for practical applications. Here, we present a cost-effective, relatively simple, and high-yield fabrication approach to construct highly sensitive and ultrastable piezoresistive sensors using a bioinspired hierarchically structured graphite/polydimethylsiloxane composite as the active layer. In this fabrication, a commercially available sandpaper is employed as the mold to develop the hierarchical structure. Our devices exhibit fascinating performance including an ultrahigh sensitivity (64.3 kPa-1), fast response time (<8 ms), low limit of detection of 0.9 Pa, long-term durability (>100 000 cycles), and high ambient stability (>1 year). The applications of these devices in sensing radial artery pulses, acoustic vibrations, and human body motion are demonstrated, exhibiting their enormous potential use in real-time healthcare monitoring and robotic tactile sensing.

Atomization of High-Viscosity Fluids for Aromatherapy Using Micro-heaters for Heterogeneous Bubble Nucleation.

The development of a novel lead-free microelectromechanical-system (MEMS)-based atomizer using the principle of thermal bubble actuation is presented. It is a low-cost, lead-free design that is environmentally friendly and harmless to humans. It has been tested to be applicable over a wide range of fluid viscosities, ranging from 1 cP (e.g., water) to 200 cP (e.g., oil-like fluid) at room temperature, a range that is difficult to achieve using ordinary atomizers. The results demonstrate that the average power consumption of the atomizer is approximately 1 W with an atomization rate of 0.1 to 0.3 mg of deionized (DI) water per cycle. The relationships between the micro-heater track width and the track gap, the size of the micro-cavities and the nucleation energy were studied to obtain an optimal atomizer design. The particle image velocimetry (PIV) results indicate that the diameter of the ejected droplets ranges from 30 to 90 µm with a speed of 20 to 340 mm/s. In addition, different modes of spraying are reported for the first time. It is envisioned that the successful development of this MEMS-based atomizing technology will revolutionize the existing market for atomizers and could also benefit different industries, particularly in applications involving viscous fluids.