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Description
EEG, ECG and EMG are a few of the most widely used diagnostic tools in the medical industry. Sensors and conductive electrolyte gels are used to transmit brain waves and cardiac signals through the skin with the requirement of preparing the skin by abrasion and hair removal. Different types of sensors are available such as dry, semi-wet and wet. Each of the three categories in theses sensors possess their pros and cons. Semi-wet sensors fall in the type of category which combine the advantages of the dry and wet types and provide better results. The first aim in our study was the manufacturing and design, testing, development and analysis of porous semi-wet sensors with varying levels of porosity. Spark Plasma Sintering was the manufacturing method chosen because of its ability to vary porosity during the densification process. Porosity was controlled by varying the temperature, current and time duration of the experiments. Porosity was an important factor for this study as it determines the amount of conductive gel the sensors can absorb into their internal porous structure. Using a porous sensor with a conductive gel embedded into it improved the impedance analysis results of the sensors. Impedance analysis was performed by using an Agilent 4294a Impedance Analyzer. Impedance analysis is an important measure of performance in terms of behaving as a part of a circuit. Due to the electrode-electrolyte-skin interface (EESI), there is a presence of an impedance at this interface and typically, for best results the interface should have an impedance as low as possible across a wide frequency spectrum. The lowest impedance possible ensures the lowest possible noise and hence, a better transmission for the signals across the EESI. This provides accurate and precise readings in the measurement of EEG, ECG and EMG signals. The second aim in our thesis is to create a mathematical equation and a model capable of predicting the impedance properties of a bio-potential sensor. The promising results of this study has shown a potential for a new direction in the overall design and manufacturing of bio-potential sensors and room for research and development.
