Highly sensitive pressure sensing coatings based on silicone/expandable microspheres composites

with the development of flexible electronic technology, sensors are widely applied in wearable and implanted electronic devices such as electronic skin. As a basic component, pressure sensors with high sensitivity and flexibility have received enormous attention. Capacitive pressure sensors are the most popular type of pressure sensors so far because of the easy construction method and low power requirement. And how to enhance the sensitivity and repeatability is key to the wide application of the capacitor- based pressure sensors. Here, we demonstrate an easy and low cost method to achieve a dielectric layer with sensitivity increased to nearly 20 times compared with pure elastomer- based dielectric layer. We combine a silicone elastomer with expandable microspheres, which will expand to nearly four times when heated. Therefore, the silicone/expandable microsphere composites have a large amount of ordered "air bubbles", similar to a foam structure. The generated dielectric layer we get after curing has lower modulus of elasticity and thus higher sensitivity after being compressed. Moreover, this composite can be used as pressure sensitive coatings. Compared to traditional pressure sensor based on thin films, the coating can be applied to large surface areas and surfaces with various geometries.