Carbon Nanotube Polymer Composite Based Electrodes with Ability to Adhere to Hairy Skin for Application in Electrophysiological Sensing
Shyam, Abhijith Balamuraleekrishna
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Biopotential recordings such as electroencephalogram (EEG) and electrocardiogram (ECG) measurements have applications in medical diagnosis, health care, human-machine interface, entertainment, etc. Electrodes are an important part of biopotential acquisition systems affecting the quality of recorded signals, comfort to the user, and the cost. Many conventional electrodes are either expensive or disposable, many are rigid and non-conformal to the skin, and some cause irritation and allergic reaction due to the use of aggressive chemical adhesives. Further, Silver/Silver Chloride (Ag/AgCl) electrodes are the only medical grade electrodes available for EEG measurements from the scalp. They are placed using EEG hats and a conductive gel is filled between the electrode and the scalp. Sometimes this gel leaks out causing shorting between consecutive electrodes. Such systems consume time to place on the head, requires assistance from experts, and restricts the user movements. Non-medical grade dry electrodes are used as an alternative to Ag/AgCl electrode setups for EEG measurements, but they require mechanical support to attach, and therefore, they are susceptible to motion artifacts. Hence, there is a need for a soft wearable electrode that is cost-effective, reusable, and can adhere to the skin regardless of the level of hair coverage and topology of the skin. This thesis presents a novel soft reusable carbon-nanotube-polymer composite based electrode capable of biopotential recording from a high dense hairy area such as the scalp. The electrode consists of an array of tulip-like microstructures that utilizes suction force in combination with the use of trace amount of medical-grade conductive gel to achieve sufficient adhesion force and conformability to hairy skin for biopotential recording. A novel low-cost scalable fabrication process was developed, and mathematical and experimental analysis of capillary rise that plays a key role in the optimization of the fabrication process was carried out. The proposed electrode was fabricated and electrophysiological signal measurements were performed. The electrode can adhere to the skin conformably resulting in low electrode-skin interface impedance and good signal to noise ratio. The electrode is found to be very comfortable to the users and capable of recording ECG and EEG for an extended amount of time.
URI for this recordhttp://hdl.handle.net/1974/28074
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