Elastomers filled with exfoliated graphite as compliant electrodes

A compliant electrode material has been realized by blending an insulating polydimethylsiloxane (PDMS) elastomer with a conductive exfoliated graphite filler, which was produced by microwave irradiation. The conductivity and stiffness of the electrodes were determined as a function of filler concentration. These materials exhibited a low percolation threshold: above 3 wt.% loading they became conductive, with conductivities reaching as high as 0.4 S/cm. They remained elastomeric upon loading up to 25 wt.%, having a Young’s modulus of only 1.4 MPa. This modulus (corresponding to a 220% increase compared to the unloaded PDMS) is the lowest reported for loaded elastomers above the percolation threshold. Scanning electron microscopy showed that the composites contained small voids, unlike unloaded PDMS, which might be responsible for the low modulus. The performance of these electrodes is comparable to that of PDMS loaded with carbon nanotubes, but the exfoliated graphite material can be produced at a fraction of the cost.