A layered sensor for simultaneous, spatially coincident softness and moisture measurements

This paper proposes a layered sensor for the simultaneous measurement of the softness and surface moisture of an object, at the same position. In the proposed sensor, a thin stainless steel film is pasted on a polyvinylidene difluoride (PVDF) film. The voltages in the stainless steel and PVDF films are generated because of electrostatic and piezoelectric effects, and the resulting waveforms can be measured while the proposed sensor repeatedly contacts and releases the object. The voltages in the films depend on the softness and surface moisture conditions of the object. The proposed sensor therefore makes it possible to measure the softness and surface moisture of the object using the voltage waveforms. Here, we present the relationship between the measured voltages obtained using the proposed sensor and the volume of distilled water infiltrated into the filter paper on the surface of the object, and the relationship between the voltages and the softness of the object. In addition, the potential of the proposed sensor for applications is discussed.