Conductive silicone elastomers electrodes processable by screen printing

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.

Stretchable Carbon and Silver Inks for Wearable Applications

“…To replace conventional inks for use in wearable electronics new stretchable inks must first develop competitive electrical properties relative to conventional inks. The GNP/CB/TPU ink showed improved electrical performance when compared with similar inks in the literature [13,22,29] with a bulk resistivity of 0.196 ± 0.013 Ω•cm, which is close to the performance of conventional conductive inks [18,20]. A novel GNP/CB/TPU ink has been developed that could maintain electrical conductivity up to 300% nominal strain, cyclic straining to 100% and showed good resistance to compression.…”

“…Coating textiles with conductive materials has been identified as a way to add functionality, with recent applications including ultra-thin rechargeable batteries [ 10 ], healthcare monitoring and the measurement of health parameters [ 5 , 6 , 7 ], electronic entertainment devices [ 5 ], electroluminescent displays [ 11 ], and electrothermal heating [ 12 ]. Previously developed stretchable inks have been printed using techniques such as hand casting [ 13 ], mask printed [ 2 ], inkjet [ 6 ], stencil printing [ 14 , 15 ], screen printing [ 1 , 6 , 11 ], and flexography [ 6 ]. Inkjet printing requires inks that have well defined and narrow rheological parameters.…”

Characterization of home-made graphite/PDMS microband electrodes for amperometric detection in an original reusable glass-NOA®-PDMS electrophoretic microdevice

“…The paste was made in a plastic flask by properly mixing both components by hand with a spatula until complete integration of graphite powder and homogeneous paste, as already mentioned in the literature [20]. Other technics can be employed to mix both components, such as the use of a miller [18] or dispersion of components in toluene for easier mixing [16]. Then, the C/PDMS paste was spread with a spatula on the surface of the PDMS mold in order to fill the molded microchannel.…”

“…Carbon/PDMS (C/PDMS) was mainly used for the conception of sensors for mechanical application [12] and phosphate monitoring [13], obtained by casting appropriate C/PDMS composite in 3D-printed molds, or used as material for strain and temperature sensing [14]. Actually, the resistivity of the material changes with the temperature, allowing for good heat sensing in robotics [15] and possible piezosensor [16] since the resistivity is also affected by the composite strain. Indeed, introduced for the first time in microsystems for valves and pumps fabrication [17], C/PDMS composite conductivity and mechanical properties have been characterized [18], showing the effect of mechanical stress on the electrical capacity.…”

Rapid and Low Cost Manufacturing of Cuff Electrodes

“…We selected our electrode material, a CB composite ( Reyes et al, 2014 ; Eklund and Kjäll, 2019 ), so that it would integrate seamlessly with the silicone body of the cuff. Graphitized carbon has similar characteristics to CB, but CB was chosen since its composite with silicone has more favorable bulk conductivity ( Quinsaat et al, 2019 ). Several other silicone composites, such as those of platinum powder ( Minev et al, 2015 ; Schiavone et al, 2018 ) and carbon nanotubes (CNTs) ( Behrens et al, 2018 ; Kim et al, 2018 ), demonstrate better charge transfer impedances.…”