Advanced Flexible Bioelectrodes for Next-Generation Implantable Triboelectric Nanogenerators

The fabrication of novel bioelectrodes using electrospun nanofibers and a prototype for a sustainable triboelectric nanogenerator (TENG) is explored in this study. Poly(lactic acid-caprolactone) (PLCL) was electrospun as the matrix of the bioelectrode and functionalized with a commercial graphene XT3. Afterward, the fibers were coated with graphene ink (Gr.ink) or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The average diameter of nanofibers increased multifold after coating. PEDOT:PSS-coated fibers showed the highest Young's modulus at 98 MPa. The nanofiber mats did not show decreased metabolic activity below the cytotoxic threshold. Graphene-functionalized PLCL fiber coated with Gr.ink showed a significant decrease in proliferation compared to untreated cells. The tested mats did not support human dermal cells' adhesion. The nanofibers blended with graphene and coated with PEDOT:PSS showed the highest conductivity, sufficient for use in TENG devices. A TENG device was assembled using PEDOT:PSS-covered PLCL/graphene fiber mats as electrodes and poly(lactic acid) with poly(glycerol sebacate) as active contact layers. The TENG device achieved a power density of 1.9 mW m^-2 and, during 1 min of operation, charged the capacitor to a voltage corresponding to 71 nJ of stored energy. The TENG module proposed could address the energy demands of healthcare monitoring and wearable electronics, sustainably.