A Highly Sensitive Flexible Capacitive Pressure Sensor With Wide Detection Range Based on Bionic Gradient Microstructures

Introducing microstructures into a flexible pressure sensor is an effective way to improve performance of the sensor. However, existing methods for preparing microstructures in sensors, such as the artificial template method, not only are time consuming and costly but also have restrictions on the diversity and complexity of the achieved microstructures. Therefore, leaves of plants that possess abundant microstructures on surfaces can be used as templates to prepare microstructures in pressure sensors. For this reason, we have developed a flexible capacitive pressure sensor with microstructured dielectric layer and electrodes by a simple and convenient way. Specifically, the polydimethylsiloxane (PDMS) electrode was obtained by transforming the microstructures and a nonflaking multi-walled carbon nanotubes (MWCNTs) conductive layer simultaneously from an indocalamus leaf template. The dielectric layer with double-sided microstructures was formed by molding two indocalamus leaves on both sides. All the microstructures of electrodes and dielectric layer are beneficial to increase the degree of deformation thus improves the sensitivity and detection range efficiently. As a result, the obtained flexible pressure sensor exhibits a high sensitivity of 2.012 kPa
$^{-1}$
, a fast response time less than 20 ms, good durability of 1000 cycles, and a wide detection range up to 100 kPa. In addition, we demonstrated the availability of the designed sensor in the monitoring the tactile pressure signals and human movements. The experimental results confirm that the proposed capacitive pressure sensor has a great potential in applications, such as electronic skin, wearable devices, and intelligent robots.