A Universal Biocompatible and Multifunctional Solid Electrolyte in p‐Type and n‐Type Organic Electrochemical Transistors for Complementary Circuits and Bioelectronic Interfaces

Abstract The development of soft and flexible devices for collection of bioelectrical signals is gaining momentum for wearable and implantable applications. Among these devices, organic electrochemical transistors (OECTs) stand out due to their low operating voltage and large signal amplification capable of transducing weak biological signals. While liquid electrolytes have demonstrated efficacy in OECTs, they limit its operating temperature and pose challenges for electronic packaging due to potential leakage. Conversely, solid electrolytes offer advantages such as mechanical flexibility, robustness against environmental factors, and ability to bridge the interface between rigid dry electronics systems and soft wet biological tissues. However, few systems have demonstrated generality and compatibility with a wide range of state‐of‐the‐art organic mixed ionic‐electronic conductors (OMIECs). This paper introduces a highly stretchable, flexible, biocompatible, self‐healable gelatin‐based solid‐state electrolyte, compatible with both p‐ and n‐type OMIEC channels while maintaining high performance and excellent stability. Furthermore, this nonvolatile electrolyte is stable up to 120 °C and exhibits high ionic conductivity even in dry environment. Additionally, an OECT‐based complementary inverter with a record‐high normalized‐gain of 228 V⁻¹ and a corresponding ultralow static power consumption of 1 nW is demonstrated. These advancements pave the way for versatile applications ranging from bioelectronics to power‐efficient implants.