Highly conductive, stretchable, durable, skin-conformal dry electrodes based on thermoplastic elastomer-embedded 3D porous graphene for multifunctional wearable bioelectronics

Long-term bioelectric potential recording requires highly reliable wearable dry electrodes. Laser-induced graphene (LIG) dry electrodes on polyimide (PI) films are difficult to conform to the skin due to the non-stretchability and low flexibility of PI films. As a result, high interface impedance and motion artifacts can occur during body movements. Transferring LIG to flexible substrates such as polydimethylsiloxane (PDMS) and Ecoflex allows for stretchability and flexibility. However, the transfer process produces a significant loss of conductivity destroying the structural function and electron conduction properties of the LIG. We found robust physical and chemical bonding effects between LIG and styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomer substrates and proposed a simple and robust low-conductivity loss transfer technique. Successfully embedded LIG onto SEBS to obtain high stretchability, high flexibility, and low conductivity losses. Electrophoretic deposition (EPD) of poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) on LIG forms an ultrathin polymer conductive coating. The deposition thickness of the conductive polymer is adjusted by controlling the EPD deposition time to achieve optimal conductivity and chemical stability. SEBS/LIG/PEDOT:PSS (SLPP) dry electrodes have high conductivity (114 Ω/Sq), stretchability (300%) and reliability (30% stretch, 15,000 cycles), and low electrode-skin impedance (14.39 kΩ, 10 Hz). The detected biopotential signal has a high signal-to-noise ratio (SNR) of 35.78 dB. Finally, the feasibility of SLPP dry electrodes for long-term biopotential monitoring and biopotential-based human-machine interface control of household appliances was verified.

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