Flexible Dry Electrodes for Acquiring Electroencephalogram Signals

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Due to drawbacks of wet electrodes such as the need for conductive gel and scalp preparation, Avertus Inc.uses two different kinds of dry electrodes in the current electroencephalogram (EEG) recording headsets.Electrodes for hairy locations are equipped with straight macroscale gold plated retractable pins, whereaselectrodes for non-hairy locations are a conductive textile over conductive foam. Pin electrode becomeuncomfortable with time for people with thin hair because the springs in the pin electrodes create pressure.They are an injury hazard under impact condition and the retractable nature of the pin electrodes makes thedevice bulky. Moreover, using two different kinds of electrodes causes the impedance mismatch issue. In thisproject, we will develop a low cost flexible conductive material and fabricate electrodes from it. A conductivepolymer composite (CPC) consisting of polydimethylsiloxane (PDMS) and metal nanoparticles (Nps) withconductivity >1000 S/m will be prepared as electrode material. Electrodes for hairy and non-hairy locationswill be produced from the CPC in different shapes for scalps with different contours. To characterize theperformance for each electrode structure the contact impedance between the dry skin and electrode will bemeasured. The fabricated electrodes will be integrated with the Avertus's prototype headset and EEG signalswill be recorded. Effect of long-term usage, sanitization and multiple usage on the electrode performance willbe evaluated. The proposed flexible conductive dry electrodes will miniaturize the headset and allow it to beworn comfortably and safely for long time. The use of same material for hairy and non-hairy locationelectrodes will remove the impedance mismatch issue in the current headset.