Evaluating the suitability of thick-film TiO2 capacitors for use in a wireless pressure measurement system

In this work, screen-printing onto glass and polymer substrates was used to form capacitors with an active area of 2 x 3 mm(2). The dielectric was formed using a polymer paste with TiO2 as the functional ingredient. Devices prepared on glass substrates were tested as strain gauges. Their GF was measured to be 30. This is higher than the standard values (3 - 15) recorded for gauges based on oxide materials. It is thought that the higher sensitivity is a result of the preparation method and small crystallite size of the TiO2 powder. After quantifying the materials sensitivity, the sensors on polymer substrates were attached to planar and cylindrical surfaces. They were then incorporated into a wireless pressure measurement system, consisting of a small size interface circuit and a transmitter. The receiver outputs a voltage reading Corresponding to the sensor capacitance. Each device was placed in a liquid environment so that it could be exposed to hydrostatic pressure. A high sensitivity to pressure changes with low hysteresis was observed. It is thought that this system could be used to wirelessly monitor pressure changes in a variety of difficult to reach environments. (c) 2005 Elsevier B.V. All rights reserved.