Photocured, highly flexible, and stretchable 3D-printed graphene/polymer nanocomposites for electrocardiography and electromyography smart clothing

Abstract

This work focuses on the development of photocured, highly flexible and stretchable 3D-printed graphene/polymer nanocomposites for electrocardiography and electromyography smart clothing. We combined acrylate monomers and oligomers in different proportions to prepare photocurable resins with good stretchability and resilience. Graphene was then added to introduce conductivity to the photocured resin and to enhance its flexibility. This resin was used to 3D print sample patterns with microneedle surface structures. The sample patterns were successfully used as sensing components for the detection of human body signals. Two methods were compared to avoid graphene aggregation: (1) the addition of styrene maleic anhydride (SMA) to enable physical adsorption via π–π interactions between the aromatic rings and graphene; and (2) the addition of polyetheramine (PEA), which creates steric effects with graphene. An amphiphilic dispersant was prepared by grafting SMA onto PEA, and the ideal dispersion ratio was determined. The dispersant was mixed with photocured resin to form a graphene/photocured resin nanocomposite material. By varying the graphene content, a nanocomposite material with the lowest resistance (approximately 3 × 103 Ω/sq) and mechanical strength (tensile strength: >4 MPa, elongation at break: 320 %) was obtained. The material also demonstrated good resilience under a 50 % cycle fatigue. Finally, flat base plates that differed from those produced by conventional screen printing were 3D-printed. Materials with surface microneedle structures with different length-to-diameter ratios and inter-needle spacings were prepared, and the differences in skin contact among these materials were experimentally investigated by measuring electrocardiography and electromyography signals in humans. Our results demonstrate that highly customized 3D-printed resins with diverse and complex structures can be successfully integrated into smart clothing to monitor the physiological status of humans.