Development of wearable flexible strain sensor using light transmittance change of nano-filler embedded elastomer with micro crack

Abstract

Recently, research on flexible strain0 sensor that can be used as wearable sensor has attracted much attention. In particular, many nanomaterials-based sensors have been developed to be used as a strain sensor that can be attached to a human body. The principle of conventional flexible strain sensors is either a resistance method or a capacitance method. Conventional strain sensors have limitations in that the stability of the sensor signal is limited when the sensor is used for a long time in the resistance method, and the low sensitivity and effect from the environmental conductive material in the capacitance method. In order to solve these problems, we proposed a flexible strain sensor using a new method in which the light transmittance of the flexible material changes according to the strain. This sensor uses the principle that the light transmittance changes as cracks are formed and propagated in the carbon nanotube film embedded Ecoflex as the external tensile is applied. The sensor has a high sensitivity (~ 31.66) in the strain range 0~100% and stable response against repeated loading over a long period of time(13,000cyclic loading), and it can measure tensile strain over a wide measuring range (~ 400%). In order to utilize the sensor as wearable device, a soft package with LED and photodetector was fabricated, and using the package, it is possible to measure the bending degree of the finger and transfer to the robot arm control. It is also shown that the sensor can be used as a posture sensor using 3-axis soft packaged strain sensor.