Strain-rate independent small-strain-sensor: Enhanced responsiveness of carbon black filled conductive rubber composites at slow deformation by using an ionic liquid

Small-strain-sensors, based on conductive carbon black (CB) filled conductive rubber composites (CRCs), have been developed. An ionic liquid (IL) was used to improve the way that the piezoresistive response is independent of strain rate at small strains. Cyclic sensing behaviour at small strains was investigated under a sequential alteration of strain rates. At small strains, the CRCs without IL respond inefficiently to slow deformation cycles, giving a strain-rate dependent sensitivity. On the contrary, the presence of IL enhances the response to slow deformations. At elongations up to 3%, the loosely packed conducting parts and the sufficient rubber-filler interaction achieved with the use of an IL/CB ratio of 1.0 make the piezoresistive responses efficiently independent of the strain rates. Also, the sensitivity is at least threefold higher, compared with CRCs without IL. So, the IL enables the construction of strain-rate independent small-strain-sensor.