Fabrication of conductive dry adhesives based on hybrid carbon nanocomposites and its applications

Abstract

We first propose a conductive dry adhesives (CDA) combining gecko-inspired structures and carbon nanocomposites. Mushroom-shaped high-aspect-ratio (HAR) microstructures are replicated from Si mas-ters by using elastomeric composites made of carbon nanofillers and poly(dimethylsiloxane) (PDMS). The optimization of viscosity of prepolymer and curing conditions guarantee the defect-free replication over large-areas ($~2 in^{2}$). To enhance the electrical percolation of 1D carbon nanotubes (CNTs) in an elastomer-ic matrix at low loading of fillers (~1 wt%), a small content of higher dimensional carbon fillers (i.e., car-bon black, nano graphite, and graphene nanopowder) are added into the mixture. The co-doping of gra-phene nanopowders and CNTs into the elastomeric matrix show the lowest volume resistance (~100 Ohm-cm) based on a synergetic effect in percolation at optimized mixing ratio (1:9). The measured normal adhesion force of the CDA on replicated skin surfaces ranges from 0.7 to $1.3 N/cm^{2}$, which is comparable to that of commercial 3M tape. The CDA maintains its adhesion force without severe degradation even after cyclic test up to 30 times. The newly developed dry adhesive can be used as an all-in-one type electrode system for obtaining electrocardiogram (ECG) signals from body and as an universal conductive adhesive on various substrates for operating LEDs.