Flexible Micropillar Array for Pressure Sensing in High Density Using Image Sensor

A stable flexible pressure array sensor is a key point for the development of smart robotics and prosthetic solutions. Traditional flexible pressure sensors are mainly based on piezoresistive, capacitive, and piezoelectric effect. However, pressure array sensors based on these principles need complicated wire links and complex fabrication processes. In addition, sensors based on capacitors are susceptible to interference, while piezoresistive sensors have drift problems. In this paper, a vision-based flexible device integrating a transparent substrate with a black micropillar array is proposed. An image sensor is introduced to measure pillar sectional-area variation caused by external pressure. Low-cost precision machining is used to make the mold which avoids complex fabrication process in terms of lithography process. Fabricating micropillars and substrate respectively with Ecoflex gel and polydimethylsiloxane (PDMS) implies adhesion of two polymer materials. The sensor demonstrates a considerable pressure sensitivity of 0.133 kPa⁻¹ in the pressure range 0–3 kPa owing to the softness of Ecoflex gel. Application in high-density pressure distribution measurement such as braille reading and shape recognition is presented. The device is also believed to have promising potential applications in wearable devices, for example, arterial pulse signal measurements.