Polycaprolactone-Based High-k Dielectrics: A Platform for Flexible and Biodegradable Transient Electronics

Transient electronics, designed to degrade after a defined period, are ideal for biomedical implants that eliminate the need for secondary removal surgeries and contribute to sustainable electronics by leaving no electronic waste. While significant progress has been made in developing semiconductors, electrodes, and substrates, dielectric layers for bioapplicable transient electronics that combine flexibility, self-healing capabilities, and high dielectric constants (high-k) remain underexplored. This study introduces urea-linked polycaprolactone (PCL-IU)/ionic liquid (IL) hybrids as dielectric materials. PCL-IU integrates the self-healing ability of urea bonds with the biodegradability and flexibility of polycaprolactone, ensuring biocompatibility. Incorporating 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) significantly enhanced dielectric performance, achieving a high capacitance of ∼10^-6 F/cm² at low frequencies. ZnO field-effect transistors (FETs) using PCL-IU/IL as the gate dielectric layer demonstrated stable electrical characteristics under ambient conditions and exhibited excellent performance, including a mobility of ∼60 cm²/(V s) and an on/off current ratio of ∼10⁵. Devices fabricated on flexible polyimide (PI) and degradable poly(vinyl alcohol) (PVA) substrates demonstrated stable and reliable operation, confirming the potential of PCL-IU/IL for bioapplicable transient electronics. These results position PCL-IU/IL as a versatile platform for flexible, low-power, and biodegradable devices.