An iono-elastomer based wearable strain sensor with real-time thermo-mechano dual response.

An ultra-stretchable iono-elastomer with resistance sensitive to both elongation strain and temperature has been developed by hierarchical self-assembly of an end functionalized tri-block copolymer in a protic ionic liquid (ethylammonium nitrate) followed by cross-linking. Small angle X-ray scattering experiments in situ with uniaxial elongation reveal a nanoscale microstructural transition of the hierarchically self-assembled cross-linked micelles that is responsible for the material's remarkable mechanical and ionic conductivity responses. The results show that the inter-micelle distance extends along the deformation direction while the micelles organize into a long-range ordered face-center-cubic (FCC) structure during the uniaxial elongation. Besides good cyclability and resistance to selected physical damage, the iono-elastomer simultaneously achieves an unprecedented combination of high stretchability (340%), highly linear resistance vs. elongation strain (R2 = 0.998), and large temperature gauge factor (ΔR/R = 3.24 %/°C @ 30 ºC). Human subject testing demonstrates that the iono-elastomer based wearable thermo-mechano sensor is able to effectively and accurately register both body motion and skin temperature simultaneously.