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Vivian Feig1 Helen Tran1 Zhenan Bao1

1, Stanford University, Stanford, California, United States

Mechanically compliant conductive materials for neural interfaces are desired both for recording and stimulation applications, including electroencephalography (EEG) measurements and deep brain stimulation treatments. However, whereas brain tissue is extremely soft (elastic modulus < 1 kPa) and dynamic, most inorganic conductors and dry conducting polymers are stiff (elastic modulus > 1 GPa) and inflexible. By contrast, hydrogels made with conducting polymers are promising soft electrode materials due to their high water content. We have developed a novel method for fabricating highly conductive hydrogels comprising two interpenetrating networks: one is a connected network of the conducting polymer PEDOT:PSS, while the second affords orthogonal control over the gel’s mechanical properties. With this method, ultra-low elastic moduli down to 8 kPa can be achieved without compromising stretchability (>100%) or conductivity (>10 S/m). We investigate the feasibility of these materials as electrodes for mechanically compliant neural interfaces.

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