Flexible Silk-Based Graphene Bioelectronics for Wearable Multimodal Physiological Monitoring

We introduce a skin-inspired epidermal bioelectronic patch (EBP) with unprecedented integration of graphene on silk with a facile and cost-effective fabrication process, excluding complex ink formulation. We advance the state-of-the-art by directly screen-printing pristine graphene ink on "donor" substrates like polyethylene terephthalate (PET) and successfully receiving the printed graphene traces onto silk protein-based "carrier" substrates by a controlled drop-casting, curing, and transfer printing process. The presented approach retains the conductivity of the pristine graphene ink prepared by reducing graphene oxide suspension through "green" chemistry based on a water-soluble vitamin C reagent. We demonstrate that silk/graphene epidermal patches (SGEP) can conformally attach to human skin without additional adhesives or gel materials. Our study reveals a superior response of the SGEP by successfully acquiring multimodal physiological signals such as cardiac-ECG, macular-EMG, and ocular-EOG with almost perfect correlation reaching a record high of 98.48% to those recorded simultaneously with medical-grade, pre-gelled with adhesive backings, wet Ag/AgCl electrodes.