Pressure Sensor Based on a Lumpily Pyramidal Vertical Graphene Film with a Broad Sensing Range and High Sensitivity

Highly sensitive, wide-pressure and low-frequency characterized pressure sensor based on piezoresistive-piezoelectric coupling effects in porous wood

Lightweight and highly compressible materials have received considerable attention in flexible pressure sensing devices. In this study, a series of porous woods (PWs) are produced by chemical removal of lignin and hemicellulose from natural wood by tuning treatment time from 0 to 15 h and extra oxidation through H₂O₂. The prepared PWs with apparent densities varying from 95.9 to 46.16 mg/cm³ tend to form a wave-shaped interwoven structure with improved compressibility (up to 91.89 % strain under 100 kPa). The sensor assembled from PW with treatment time of 12 h (PW-12) exhibits the optimal piezoresistive-piezoelectric coupling sensing properties. For the piezoresistive properties, it has high stress sensitivity of 15.14 kPa^-1, covering a wide linear working pressure range of 0.06-100 kPa. For its piezoelectric potential, PW-12 shows a sensitivity of 0.443 V·kPa^-1 with ultralow frequency detection as low as 0.0028 Hz, and good cyclability over 60,000 cycles under 0.41 Hz. The nature-derived all-wood pressure sensor shows obvious superiority in the flexibility for power supply requirement. More importantly, it presents fully decoupled signals without cross-talks in the dual-sensing functionality. Sensor like this is capable of monitoring various dynamic human motions, making it an extremely promising candidate for the next generation artificial intelligence products.

Wearable Pressure Sensor Using Porous Natural Polymer Hydrogel Elastomers with High Sensitivity over a Wide Sensing Range

Wearable pressure sensors capable of quantifying full-range human dynamic motionare are pivotal in wearable electronics and human activity monitoring. Since wearable pressure sensors directly or indirectly contact skin, selecting flexible soft and skin-friendly materials is important. Wearable pressure sensors with natural polymer-based hydrogels are extensively explored to enable safe contact with skin. Despite recent advances, most natural polymer-based hydrogel sensors suffer from low sensitivity at high-pressure ranges. Here, by using commercially available rosin particles as sacrificial templates, a cost-effective wide-range porous locust bean gum-based hydrogel pressure sensor is constructed. Due to the three-dimensional macroporous structure of the hydrogel, the constructed sensor exhibits high sensitivities (12.7, 5.0, and 3.2 kPa^-1 under 0.1-20, 20-50, and 50-100 kPa) under a wide range of pressure. The sensor also offers a fast response time (263 ms) and good durability over 500 loading/unloading cycles. In addition, the sensor is successfully applied for monitoring human dynamic motion. This work provides a low-cost and easy fabrication strategy for fabricating high-performance natural polymer-based hydrogel piezoresistive sensors with a wide response range and high sensitivity.