Novel coplanar capacitive force sensor for biomedical applications: A preliminary study

Nowadays the world of sensors is gaining a primary importance in the electronics field, thanks to the boom of the smartphones and IoT market. Capacitive sensors are widely involved in the most of applications, from the biomedical to the gaming industry, and they can sense a wide variety of physical quantities. In this work we focused on force sensing capacitive sensors, trying to mix two of the most in-fashion markets, sensors and polymers. Polymers industry is constantly growing and, by the constant synthesis of new bio-based molecules, it will quickly enter the most of the technology markets. We made a soft capacitive force sensor, by inserting a coplanar capacitor in a polymeric wafer structure. The involved technology is derived from the touch-sensing technique, usually involved in appliances’ user interfaces. This sensor is easy to make and cheap, and it was tested with a force of 1 N. It is waterproof and non-sensitive to moisture variation in the outer environment. It shown a sensitivity of 172 fF/N, with a resolution of 80 mN. As it is only a preliminary study, more investigations are needed in order to obtain a deeper characterization versus different environment conditions and with higher force stimuli. It will be also relevant to evaluate the behavior of the sensor by using different polymers.