Soft compressive sensor design and analysis

In this paper, a methodology of designing an absolutely soft sensor based on Eco-Flex to detect compression stimuli is proposed. The fundamental structure of this soft sensor is a soft membrane sandwiched by two stretchable carbon grease electrodes, therefore the sensor as a capacitor can convert mechanical deformation to electrical signal. When the soft sensor is subject to compression stimuli, by detecting the capacitance change resulting from geometry deformation of sensor, the applied load can be inferred. To obtain a soft sensor with high sensitivity, two structures are proposed: sensor body with and without embedded chamber. By theoretically comparing the load-capacitance curve of them, it proves that the embedded chamber can improve the sensitivity of the compressive sensor. Besides, the dimension of the chamber has a great impact on the detection range and resolution. In this paper, 4 types of dimensions were investigated, and the mechanical - electrical curves show that, a relatively thicker chamber leads to a larger detection range but smaller resolution. Experimentally, we fabricate the two structures - with and without embedded chamber, and the response agrees well with the theoretical prediction. When come to the fabrication of the sensor, because rigid electrodes constrain deformation of the sensor, an approach of fabricating a solid soft electrode based on carbon grease was proposed in this paper.