User interface to input in proportion to fingertip pressure

This paper proposes a new user interface that supplies a linear multi-value output in proportion to fingertip pressure. The principle of our proposal is to use a strain sensor to detect the strain of a chassis of a portable information terminal caused by fingertip pressure. An experimental model consisting of a detection circuit using a strain sensor and an embedded MPU was built to verify the operation. The experimental results indicate that the device supplies an extremely linear and highly accurate output that is proportional to the force of the fingertip pressure. This proposed device doesnpsilat need a specific area and thickness for input buttons in the chassis. Additionally, all components including the sensor and detection circuit are available as standard market items. Therefore manufacturing the device is inexpensive, and the circuit consumes little electric power.