Soft Photo-Ionotronics

The ability to control the movement of charged species in the circuitry of living beings and machines is essential for complex signal processing, computation, and, ultimately, higher functionality. We describe a class of photo-ion generators (PIGs) based on non-ionic photoacids that can create large (> 1000x) irreversible changes in ionic conductivity under illumination depending on the PIG species, concentration, and solvent. Incorporation of PIGs into polyurethane rubber by simple swelling methods yields soft (E > 2 MPa), stretchable, photo-ionic gels (PIGels). The resolution of photo-patterned conductivity in PIGels is less than 1 cm and demonstrates stability over several days, suggesting utility in engineered devices. Utilizing this novel class of material, we demonstrate high sensitivity mechanical sensors via conductance changes ([ΔG/G0]/σ = 20 MPa-1) and photo-writable, soft circuitry.