Date of Award


Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy


Electronic Engineering

First Advisor

Dr John Barrett


Steam sterilisation is a process of removing or killing living organisms from medical equipment using saturated steam in a steriliser at 134°C and 3 bar pressure. Monitoring of the steriliser is very important to verify whether the sterilisation cycle is adequate or not. In current practice, hospitals widely use chemical or biological indicators for monitoring the performance of the sterilisation cycle but these are simple pass/fail monitors and do not allow continuous monitoring. This thesis presents design and development of a real time wireless sensing module (WSM) for monitoring the sterilisation cycle which can be used to replace existing chemical and biological indicators. A plastic-encapsulated WSM which can survive in a steam steriliser has not been previously reported in the literature. The research therefore proceeded in two strands: the first was to characterise the circuit board and packaging materials in a supersaturated steam environment (SSE). Saturated moisture concentration, moisture diffusion coefficient and hygroscopic expansion of the materials were extracted from data collected in a series of designed experiments using a range of circuit board and plastic packaging materials. The second involved practical reliability evaluation of batteries, sensors and electronic components during steam sterilisation cycles and other reliability test conditions. Test vehicles (TVs) were then designed and used to evaluate the reliability of WSM components in SSE. The results of these evaluations allowed sensors and other components to be selected for the fabrication of the WSM. The reliability of sensor module was then investigated on 12 packaged samples in order to obtain its performance. The WSM demonstrated the ability to survive 180 sterilisation cycles and to continuously report on the steriliser internal conditions. This is believed to be the first plastic-packaged electronic module to survive multiple cycles in a medical steam steriliser.

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