In Situ Measurement of Percolation Threshold of Conductive Fillers and Integration into a Self-Healing Elastomer

Abstract

One of many research topics at IMO-IMOMEC (Diepenbeek, BE) is the optimization of the design of printed structures and read-out electronics for the construction of flexible tactile sensors. This research focusses principally on the development of stretchable conductors by blending conductive fillers with an elastomeric matrix and the determination of the percolation threshold. Unfortunately, cracks can arise in the conductor while stretching which results in a loss of conductivity. Due to this crack formation, it is necessary to synthesize a conductive matrix with good blending characteristics, a low electrical resistivity and reliable elastic properties.

In this research project, the percolation threshold of 6 different conductive fillers was determined by gradually increasing the volume percentage in a PDMS-matrix. During this experiment, an in situ measuring tool quantified the blend resistivity to find out the percolation threshold. In the second stage of the investigation, the formation of cracks was prevented by using a self-healing elastomeric matrix instead of a traditional elastomer.

The percolation experiments show that cylindrical particles have a lower percolation threshold than spherical particles. Moreover, the blend resistance of metal fillers is smaller than carbon-based particles. Finally, the integration of conductive fillers in the self-healing elastomeric matrix results in a printable ink by the addition of chloroform.