Force sensing model of capacitive hybrid touch sensor using thin-film force sensor and its evaluation

This paper suggests the concept model of hybrid touch sensor that can detect touch locations and each force component in case of single or two-point touch event. The model is to calculate each force component using known touch locations obtained from commercial projective capacitive touch module. The suggested model consists of four thin-film force sensors and a tempered glass plate instead of commercial capacitive touch sensor. The force sensors are fabricated easily by simple screen printing technique and evaluated by calibration setup. Eleven single-touch events are performed to obtain the maximum deviation error of force responses with respect to touch locations. Additionally, we perform two-point touch events using a transitional load and a dead weight load (50 g or 100 g) to verify the proposed hybrid touch model. The obtained force components are compared with two input loads. It is confirmed that the hybrid touch sensor can provide satisfactorily the location of contact and the force response. Finally, we expect that the proposed touch model can detect the touch locations and force components simultaneously in case of single or two touch events.