Wearable electronics and sensors to be incorporated into clothing, uniforms, and sporting equipment require flexible, robust soft materials with high conductivity and high extensibility- so called “stretchable electronics”. Applications include stretchable batteries, wearable sensors and integrated circuits. Fabrication of such materials usually requires the use of hybrid technology that mixes metals, polymers and conductive materials, to tie the system together electronically.

Current strategies include composite materials with “wavy” or fractal designs, micro- or nano-structured metal embedded in elastomeric matrices, biphasic solid-liquid metal thin films embedded in elastomeric substrates, composite films of carbon nanotubes or graphene and metals and polymeric materials doped with dispersions of carbon nanotubes in ionic liquids (bucky gels) which are subsequently coated with elastomeric substrates. Manufacturing of these materials involve sophisticated and complex integration of elastomeric substrates with micro- or nano-structured organic or inorganic electronic materials via multi-step and often costly processes.

We have demonstrated a simplified manufacturing process to create stretchable conductor materials applicable for stretchable electronic technologies by self-assembly of concentrated solutions of end-functionalized commercially available, in-expensive triblock copolymer Pluronic F127 in a protic ionic liquid ethylammonium nitrate, followed by micelle corona crosslinking to generate elastomeric ion gels (iono-elastomers) under UV-curing initiator. We found that these morphologies remain unchanged upon crosslinking the solutions in presence of a UV-curing initiator. The resulted materials exhibit an unprecedented combination of high stretchability, high ionic conductivity and mechano-electrical response. Importantly, the materials conductivity increases with extension, a unique and non-trivial material response.

References:

1. Chen, R.; López-Barrón, C. R.; Wagner, N. J. Book chapter for ACS Symposium Series: “Ionic Liquids: Current State and Future Directions”. In press.
2. López-Barrón, C. R.; Chen, R.; Wagner, N. J.; Beltramo, P. J. Macromolecules. 2016, 49(14), 5179-5189.
3. López-Barrón, C. R.; Chen, R.; Wagner, N. J. ACS Macro Letter. 2016, 5, 1332-1338.
4. López-Barrón, C. R.; Chen, R.; Wagner, N. J. U.S. Patent Serial No. 62/393,133, September 12, 2016.
5. 2nd place winner at NSF I-Corps Site Program pitch competition. www.delawareonline.com