Force Sensor Using Ionic Liquid Capillary Bridge

We propose a force/pressure sensing method utilizing a stretched capillary bridge of ionic liquid (IL). In the proposed method, an ionic liquid droplet is stretched by two electrodes, one of which is deformable. The force or pressure applied to this electrode causes the capillary bridge to deform and change its impedance. Thus, the applied force/pressure can be measured by measuring the impedance of the capillary bridge. In comparison with the conventional method based on measurement of interfacial capacitance of the IL droplet, the proposed method offers several advantages such as high sample rate and the capability to miniaturizing the sensor without decreasing the sensitivity. To shed a light on the optimization of the sensor design, we investigated the dependence of the impedance of the capillary bridge on the stretched length and the dependence of the impedance change due to the stretching on the volume of the droplet. Finally, we demonstrated the applications of this method as a force sensing cantilever and a pressure sensor that can measure pulse wave.