Photopatternable and electrically conductive exfoliated graphite nanoplatelet-reinforced SU-8 nanocomposites for electrical lead micropatterning

Abstract

Abstract There is an ever-increasing demand for polymer-based electrical leads patterned on polymer substrates of any shape to connect two electrical components. Much, however, still remains challenging about electrical leads made of polymer nanocomposites that have high affinity to polymer substrates and outstanding applicability to curved surfaces, unlike metals. This leads to the need for development of photopatternable and electrically conductive polymer nanocomposites and, by extension, comprehensive understanding of the constituent and processes involved in their development. Here, a set of polymer nanocomposites incorporating exfoliated graphite nanoplatelet (xGnP) into SU-8, xGnP/SU-8 nanocomposites, are developed as photopatternable and electrically conductive nanocomposites for electrical lead micropatterning. The inclusion of xGnP, carbon-based conductive nanofiller, is intended to provide electrical conductivity and the use of SU-8, photocurable host polymer, is designed to achieve both patternability and strong adhesion to polymer surfaces. First, the patterning characteristics of xGnP/SU-8 nanocomposites are explored with regard to patterning thickness and patterning error; The dependence of patterning characteristics on xGnP content and UV exposure dose are extensively investigated. Next, we explore an evolution in the electrical conductivity of xGnP/SU-8 nanocomposites with variation of xGnP content to understand their electrical behavior. Finally yet importantly, the applicability of xGnP/SU-8 nanocomposites to electrical lead micropatterning is demonstrated by photopatterning an electrical circuit for light emitting diode (LED) chips using the xGnP/SU-8 nanocomposites on polydimethylsiloxane (PDMS) substrate. The findings of this study will contribute to a significant growth of polymer-based electrical leads and better understanding of photopatternable and electrically conductive nanocomposites.