Conductive silicone elastomers electrodes processable by screen printing

Jose Enrico Q Quinsaat,Frank A Nüesch,Dorina M Opris,Ronny Krämer,Mihaela Dascalu,Daniel Häfliger,Iurii Burda

doi:10.1038/s41598-019-49939-8

Abstract

Conductive inks consisting of graphene and carbon black conductive fillers into a polydimethylsiloxane (PDMS) matrix, which can be processed into thin films by screen printing are developed. The influence of filler composition and content on mechanical and electrical properties of the conductive composites is investigated. The best composites were evaluated as electrode material for dielectric elastomer actuators and for piezoelectric sensors. With increasing filler content, the electrical properties of the resulting composites of graphite nanoplates (GNPs) or a binary mixture of GNPs and carbon black (CB) with PDMS (Mw = 139 kg/mol) are enhanced. Hence, PDMS composites filled with GNPs (42 wt.%) or a binary mixture of GNPs/CB (300/150 ratio, 30 wt.% of total filler loading) exhibited constant contact resistance values of 0.5 and 5 Ω determined in life-cycle test, respectively, thus rendering them suitable as electrode materials for piezosensors. On the other hand, dielectric elastomer actuators require more flexible electrode materials, which could be tuned by varying the polymer molecular weight and by reducing the filler content. Therefore, a composite consisting of PDMS (Mw = 692 kg/mol) and a binary filler mixture of GNPs/CB (150/75 ratio, 18 wt.% of total filler loading) was used for producing the electrodes of dielectric elastomer transducers (DETs). The produced DETs with different electrode thicknesses were characterized in terms of their performance. The negligible hysteresis of the electrode materials is favorable for sensor and actuator applications.

Highlights

The tremendous development of elastic piezoelectric sensors and dielectric elastomer transducers (DET) in the last decade stimulated the search for conductive stretchable electrode materials by the research community worldwide
Previous reports show that the mixture of silver nanoparticles/graphene[15], silver nanoparticles/ CNTs28, graphite/CB29, graphite/MWCNTs30, or carbon black (CB)/CNTs31–33 led to composites with high conductivities which is attributed to the combination of large and small structures beneficial for creating a large conductive network within the composite
After finding the optimum conditions for the formation of homogenous composites and for the cross-linking in thin films, the step was to optimize their electrical conductivity. To achieve this we investigated the conductivity of composites with different content of graphene nanoplates (GNPs), CB, and a mixture of the two

Summary

Introduction

The tremendous development of elastic piezoelectric sensors and dielectric elastomer transducers (DET) in the last decade stimulated the search for conductive stretchable electrode materials by the research community worldwide. To further enhance the electrical conductivity of the PDMS matrix, the composites with both fillers, i.e. binary mixtures of CB and GNPs, were prepared.

Results

Conclusion