Development of flexible capacitive sensor for three-dimensional force measurement

Abstract

This paper presents the development of flexible capacitive sensor for measuring three dimensional forces to monitor and early detection of pressure ulcers. The wide range of capacitive sensors can be used for many industrial applications which include the measurement of applied pressure and force. The accurate measurement of pressure becomes essential key parameters to analyses the behavior of sensor based biomedical measurement system for different applications. In most situations, people with severe motor impairments have very low sensitivity in parts of the body that come into contact with supporting surfaces such as beds and wheel chairs. As a result of the pressure surpassing the tissue for an extended period of time, tissues are deprived of oxygen and necessary nutrient which leads to the development of pressure ulcers. Monitoring three-axis force that people with severe motor impairments exert on supporting surfaces is one technique to reduce the risk of pressure ulcer formation. This paper proposed the novel design of capacitive sensor to monitor three axis forces in all dimensions. Here, a custom developed sensor with capacitance to digital converter is used to convert the sensor's capacitance to a digital value. The proposed converter can be used to measure the capacitance in the range of 0 to 260pF and stored in device memory for easy access and processing. The low power ARM Cortex M3 processor with serial communication protocol is configured in embedded programming environment to acquire the signal from the proposed sensor and the capacitance variation is displayed on the OLED.