Femtosecond laser direct writing of graphene oxide film on polydimethylsiloxane (PDMS) for flexible and stretchable electronics

Graphene, an allotrope with a two-dimensional arrangement of carbon atoms, has attracted great interest owing to its exceptional properties. Currently, graphene can be synthesized by using several methods, wherein, the photoreduction of graphene oxide (GO) by femtosecond laser direct writing (FsLDW) has gained much attention because its mask-free process enables high-resolution patterning in an arbitrary fashion. Furthermore, FsLDW allows for a tunable degree of reduction by simply adjusting the laser processing parameters, resulting in designable patterns with tunable electrical conductivity. In this paper, we used FsLDW to precisely fabricate arbitrarily-designable reduced graphene oxide (rGO) patterns on polydimethylsiloxane (PDMS), a flexible and stretchable substrate. Furthermore, the experimental characterizations of GO and rGO were conducted to confirm and characterize the reduction of GO. As a typical example, a flexible and stretchable graphene-based strain sensor was fabricated using FsLDW of GO on PDMS. By attaching directly to the skin or even embedding into clothes, these strain sensors can be applied to the development of various applications such as detection of human motion or monitoring of personal healthcare and therapeutics.