Stretchable Organic Electrochemical Transistors Based on Non-destructive Microlithography

Stretchable organic electrochemical transistors (OECTs) have emerged as promising platform for skin-like electronics due to ion-to-electron signal transduction and in situ amplification with deformability. To realize highly integrated stretchable OECT systems, key elements in device circuitry must provide efficient ion-electron coupling, high stretchability, and scalable microfabrication simultaneously. Ionic elastomers are particularly attractive as electrolytes because they enable efficient electrochemical gating while retaining mechanical compliance. In addition, direct photo-patterning of ionic elastomers offers a promising route toward high-density device integration. However, conventional photo-patternable ionic elastomers often suffer from reduced ionic conductivity and mechanical deformability owing to restricted segmental motion of polymer after crosslinking. Also, stretchable polymer semiconductors typically exhibit limited ion transport behaviors or poor compatibility with lithographic fabrication.
Here, we present stretchable OECT based on ionic elastomer network (IEN) and polymer semiconductor network (PSN), in which a thermoplastic polyurethane matrix containing ionic liquid and a polymer semiconductor matrix are photo-crosslinked using ethylene oxide (EO)-integrated crosslinker. The EO moieties serve two major capabilities: i) ion compatibility, and ii) inherent stretchability. As a result, the IEN and PSN enable reduced ionic resistance, fast ion diffusion, and high channel capacitance while maintaining mechanical deformability. Also, they can attain high resolutions down to 5 um and 2 um for IEN and PSN, respectively. Leveraging this materials platform, we demonstrate high-density stretchable OECT arrays that simultaneously achieve intrinsic stretchability, high device performance, and scalable integration. Consequently, we believe that our approach can offer new insights into highly integrated stretchable iontronics.