A High-Performance Flexible Capacitive Pressure Sensor With 3-D Printed Hemispherical Graded Microstructures

In recent years, flexible pressure sensors have been deployed in various fields due to their advantages of high sensitivity, low detection limits, wide operating range, and fast dynamic response. Introducing microstructures into the sensitive layer of a sensor is an effective method to improve its performance. However, most currently adopted microstructures are often obtained through photolithography, etching, or replication from naturally existing templates, which results in the poor designability of the proposed sensor. To address this issue, a rational design method for microstructures based on numerical simulation analysis has been reported in this article. At first, a series of numerical simulations was conducted to study the influence of microstructure shapes and size parameters on sensor performances. The results indicate that hemisphere structures with a radius of $500 ~\mu \text{m}$ exhibit the largest capacitance variation under the same pressure conditions. Then, a capacitive flexible pressure sensor with a 3-D-printed hemispherical graded microstructure (polydimethylsiloxane) PDMS dielectric layer has been presented. The fabricated sensor exhibits a high sensitivity of 1.357 kPa−1 within the range of 0–5 kPa and a broad detection range of 0–500 kPa. Simultaneously, the sensor also demonstrates a fast dynamic response (< 60 ms), a low detection limit (approximately 100 Pa), and remarkable stability (over 3000 cycles). All these exceptional performances confirm the designed sensor with significant potential for in the field of physiological signal monitoring.