Transparent stretchable compliant electrodes for hydrophobic substrates using PEDOT:PSS/PDMS composite ink

Abstract

Recently, dielectric elastomers like polydimethylsiloxane (PDMS) and acrylic elastomers have become prevalent as foundational materials for wearable sensors and electroactive polymers. Nevertheless, a significant challenge in using these elastomers lies in their notably low surface energy, presenting issues for electrode deposition and adhesion. In applications like sensors and electroactive polymers (EAPs), it is essential to cover dielectric elastomer substrates with thin, stretchable electrodes. However, the low surface energy of these substrates complicates the production of a thin, uniform film using ink materials. Materials based on nanowires or metal vapor deposition exhibit poor adhesion to PDMS, easily peeling off and resulting in unreliability. Surface treatments, such as exposure to plasma and UV light, can temporarily elevate the surface energy of PDMS. However, this treated surface reverts to its original state within a few hours, forming a brittle surface layer prone to cracking when stretched. Notably, such treatments are ineffective for acrylic elastomers. To overcome these challenges, we have developed a viscous liquid composite ink consisting of PEDOT:PSS and PDMS (A/B). This ink can be easily applied to pristine PDMS substrates through methods like blade casting and screen printing. The coatings form a highly transparent and stretchable surface layer, acting as a compliant electrode. These coatings created using PEDOT:PSS/PDMS composite ink with Elastosil (PDMS) and 3M VHB 4910 as dielectric elastomers, result in transparent dielectric elastomer actuators. The actuation strain and breakdown fields are slightly lower than those in dielectric elastomer actuators (DEAs) with conventional graphite electrodes. However, the self-cleaning capability of these PEDOT:PSS/PDMS composite electrodes provides an advantage over conventional electrodes, particularly in terms of resistance to localized dielectric breakdown of DEAs.