Multimaterial 3D Printing of Poly(ionic liquid) Diodes for Soft Ionotronic Robots

Overcoming long-standing challenges in soft robotic control requires new strategies for coupling perception and computation in soft, multifunctional materials. Ionotronic approaches have largely remained unexplored despite recent progress in soft ionotronic actuation and power methods. Poly(ionic liquids) are a promising class of materials that can combine elastomeric behavior with high ionic conductivity. However, current methods of patterning soft poly(ionic liquid) elastomers are limited, requiring low-throughput procedures to produce even simple forms and devices. To address this challenge, we present an integrated, multimaterial 3D printing and material design framework for fabricating poly(ionic liquid) composites as stable, ionotronic sensing and control elements for soft robots. We harness the chemical modularity of poly(ionic liquids) to formulate four inks that enable ionotronic devices to be printed in one complete process. In addition to printing and characterizing ionic diodes fabricated with our technique, we demonstrate other architectures and devices enabled by our method. We anticipate that our work can be adapted to equip next-generation soft robots with soft controllers, on-board power generators, and distributed sensing mechanisms.