Flexible Fe3 +-doped gelatin/poly(acrylate-co-acrylamide) conductive hydrogels for biopotential acquisition, salt recognition, and supercapacitors
Herein, a novel Fe 3+ -doped gelatin/poly(acrylate-co-acrylamide)(GPFe) ionically conductive hydrogels were fabricated using a simple and mild route. The GPFe hydrogel exhibited satisfactory mechanical strength, antifatigue, self-recovery, moisture-retention, anti-swelling, and electronic properties. As a result, the GPFe hydrogels were used as saline-permeable materials to fabricate semi-dry electrodes for detecting subtle electrophysiological signals such as electroencephalogram, electrocardiogram, and electromyogram. The proposed hydrogel semi-dry electrode demonstrated a relatively low and stable electrode-scalp impedance (17.8 ± 3.69 kΩ at 10 Hz) and could capture expected neuroelectrophysiological responses with similar signal patterns and amplitudes to the golden standard wet electrodes. The grand average temporal correlation coefficients between semi-dry/wet electrodes for eyes closed/open and steady-state visual evoked potential paradigms were 0.92 ± 0.36 and 0.93 ± 0.24, respectively, confirming the feasibility on real-life brain-computer interfaces. More importantly, the hydrogel semi-dry electrode overcame the dilemma that existing wet and dry electrodes cannot balance signal quality and user friendliness. In addition, the GPFe hydrogel-based detector could distinguish between different types and concentrations of salt solutions and used as efficient electrolyte to construct flexible supercapacitors. The hydrogel-based supercapacitors showed high surface capacitance (6.25 mF cm 2 ) and maintained a good capacitance retention percentage (92.5 %) after 2000 charge-discharge cycles. Overall, the GPFe hydrogel system integrate multi-functional sensing and flexible power source, which provides valuable technical support for self-powered multi-functional wearable sensor system.
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