A Piezoresistive Tactile Sensor Array for Touchscreen Panels

Touchscreen panels (TSPs), as human-machine interfaces, have been ubiquitously adopted in our daily life, especially in consumer electronics and numerous industrial applications. However, the lack of sensing the force information in conventional TSPs draws compromises in gesture strategies and user experiences, leading to complex gestures, multi-level menus, waiting and so on. This paper investigated a piezoresistive tactile sensor array, which sensed the force amplitude of a touch event with the location information using four tactile cells. The development of the sensor array prototype has been discussed, including the design, fabrication, packaging, and tests. Each sensor in the array was tested, demonstrating the sensitivity of 0.31 mV/mN.V in the normal direction. The responses of the sensor array to a 30-mN normal force at various locations along two diagonal lines have been tested, gathering high agreements with numerical solutions. The approach for quantifying the force and location information using a lookup table based on the least square method has been discussed by the probe tests with a 50-mN force in the normal direction on the sensor array. The sensor array showed the capability to achieve the location resolution of 2 mm with tested forces ranging from 0.01 to 0.25 N. The prototype of concept shed light on reducing the number of tactile cells for touchscreen applications. Further numerical analysis indicates the sensor array has the scalability for potential applications, in which a larger area of detection is needed without increasing the number of tactile cells.