Toward Novel Wearable Pyroelectric Temperature Sensor for Medical Applications

Knowledge of an amputees' residual limb skin temperature is considered to be of particular importance as an indicator of tissue health. Temperature within the prosthetic socket typically varies over the range 25 °C to 35 °C and this warm, confined environment causes sweating which creates favourable conditions for both the growth of bacteria and an increased risk of tissue breakdown. With this in mind a wearable sensor for the real-time measurement of temperature variations at the prosthetic socket/liner interface is under development and a proof of concept prototype is presented. The sensor exploits the large pyroelectric effect present in ferroelectric lead zirconate titanate PbZr
_x
(Ti
_(1-x)
)O
₃
(PZT) and has several inherent advantages over other methods of temperature sensing. The sensing element is a low cost commercially available thick-film PZT device. Mathematical models are developed to describe the sensor immitance and response to temperature change, and both the clamped and unclamped capacitances are investigated over the range 20 °C to 40 °C. Sensor characteristics were found to be dominated by the clamped dielectric constant and operation under short-circuit conditions is found to offer a constant sensor gain over the temperature range of interest.