Dual effect of temperature and strain on the electrical response of highly sensitive silicone elastomers doped with graphene nanoplatelets

The electrical response of graphene nanoplatelet (GNP) doped silicone elastomers (PDMS and Ecoflex) are studied under the influence of temperature, strain and both at the same time. First, temperature tests indicate a positive temperature coefficient behavior of nanocomposites over a range of −20 to 80 °C, due to higher phonon/charge scattering effects and the separation of GNP because of thermal expansion. Ecoflex sensors show higher temperature sensitivity due to their higher coefficient of thermal expansion. Second, strain tests at 20 °C reveal that nanocomposites based on PDMS promote a higher strain sensitivity due to better GNP distribution. Moreover, the optimized nanocomposites exhibit exceptional gauge factor at low strain levels (110 at 1 % and 20·104 at 7.5 %). Finally, the sensitivity of the nanocomposites to strain decreased with increasing temperature due to thermodynamic degradation of the interface between the GNP and the matrix. The prevalent contact mechanisms at higher GNP contents promote a lower reduction in temperature sensitivity when increasing the GNP content. The sensitivity of the nanocomposites to temperature and strain also decreased with the number of tensile cycling loads, particularly at higher temperatures. These findings are used to select the suitable nanocomposite for temperature, strain or dual temperature-strain sensor applications.