A novel system for displacement sensing, integrated on a plastic substrate

A micro system utilizing a novel sensing principle is presented in this paper. The determination of position is performed by exploiting the heat transfer between a heating source and a sensing device. The device itself consists of an array of temperature sensing elements, fabricated entirely on a plastic substrate. A specific fabrication technology was implemented which allows direct integration with read-out electronics and communication to the macro-world without the use of wire bonding. The fabricated sensing elements are temperature sensitive Pt thermistors. The device is able to detect both the position and the motion of a heating source by monitoring the induced resistance variation on the thermistor array. The heating source which performs a one-dimensional motion in a parallel plane to the temperature sensing array can be any element that can provide a highly localized temperature field. The system operation was characterized under both steady-state and dynamic conditions. In steady state mode the sensor exhibits a resolution of ±50 μm, while in dynamic conditions the device can detect signal frequencies up to 10 Hz.