Novel Hydrogel and Conducting Polymer-based Skin Surface Electrode Design
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1065-QQ03-14
Novel Hydrogel and Conducting Polymer-based Skin Surface Electrode Design Nicolas Alexander Alba1, Gusphyl Justin1, Reecha Wadhwa1, Mingui Sun1,2, Robert J Sclabassi1,2, and Xinyan Tracy Cui1 1 Bioengineering, University of Pittsburgh, Pittsburgh, PA, 15260 2 Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, 15260
ABSTRACT Various formulations of polymeric hydrogels were synthesized and evaluated with the goal of developing a novel skin-surface biopotential electrode. Materials explored within the study included poly(2-hydroxyethyl methacrylate) (polyHEMA) in pure form or impregnated with the conducting polymers polypyrrole or poly(3,4-ethylenedioxythiophene) (PEDOT), as well as polyacrylate. The drying dynamics, ionic conductivity, and impedance of the prototype materials were characterized when applied to porcine and human skin, in order to determine their utility for a minimum preparation and low specific impedance surface electrode. The addition of a fraction of PEDOT or polypyrrole within a polyHEMA gel was found to decrease hydrogel impedance when tested within PBS, as well as on non-abraded porcine skin. A polyacrylate component added to polyHEMA had no significant effect on hydrogel impedance in PBS, but significantly reduced impedance on the porcine skin surface. Although having much lower specific impedance (impedance normalized by the contact area) than the commercial skin surface electrode (3M Red Dot), polyHEMA based electrodes require skin abrasion. Pure cross-linked polyacrylate gel was found to provide the most attractive option, and yielded competitive lowimpedance performance on non-abraded human skin. INTRODUCTION There exists in today's market a wide variety of skin-surface biopotential recording electrodes for a host of applications, such as ECG and EEG clinical procedures. ECG (electrocardiography) electrodes in particular exist in a range of embodiments, optimizing properties such as ease of placement, durability, comfort, and cost. EEG (electroencephalography) electrode development, however, has lagged behind, presumably due to the unique design requirements necessary for effective implementation. The functional requirements of EEG are demanding, including low impedance performance at low frequencies, small surface area to maximize resolution, ease of application, comfort, effective duration, safety, and cost-per-unit. Conventional EEG electrode models are only capable of meeting a portion of these requirements, and this fact has limited the scope of EEG implementation within the range of applications where it would be most useful [1]. It is known that by far the most significant obstacle to ideal electrical behavior of the electrode/skin interface is the stratum corneum of the epidermis, which acts as a barrier to ionic current and thus significantly increases the impedance of the interface. This impedance can vary significantly between individuals and testing conditions, such as variations in electrode placement, stratum corneum thickness, degree of hydration of
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