Development of low cost screen-printed piezoresistive strain sensor for facial expressions recognition systems

The ability to automatically detect human facial expressions using sensor technology can potentially improve the quality of human life. The facial expressions can indicate the intentions and physiological conditions of a person which is valuable to healthcare sector. This paper presents the development of a low-cost stretchable strain sensor for human facial expression detection by utilizing stretchable silver ink. Screen printing technique was used to fabricate the sensor on commercially available medical dressing tape, Tegaderm. Mechanical characterization was carried out for the medical tape to evaluate its ultimate tensile strength and Young’s modulus. Moreover, a new theoretical model for the hyper elastic Tegaderm film was developed based on Rivlin-Mooney two parameter model. The strain sensor exhibits several benefits such as high sensitivity, easy fabrication and conformable to human skin deformation. The sensor has the maximum gauge factor (GF) of around 84 with the highest stretchability of up to 20% strain. Experiments were conducted to evaluate the feasibility of applying the strain sensors for facial expressions detection system. Three facial expressions which are happy, sad and disgust were successfully distinguished. Due to the distinctive features of the sensor, it has wide potential applications in the field of facial expression detection, human body monitoring and robotics