Eutectic Gallium–Indium Liquid Metal Hydrogel Enables Interfacial Photogating Modulation in Organic Photoelectrochemical Transistor Biosensing

Abstract The integration of eutectic gallium–indium liquid metal (EGaIn‐LM) into photon‐regulated bioelectronics through interfacial control strategies poses challenges, such as the internal cohesion of EGaIn‐LM at room temperature, and effective interaction between targets and EGaIn‐LM. Herein, an EGaIn‐LM‐mediated multifunctional liquid metal‐hydrogel system is demonstrated for interfacial photogating modulation at zero gate bias in an organic photoelectrochemical transistor (OPECT). A manganese dioxide‐encapsulated liquid metal (EGaIn‐MnO ₂ ) template is fabricated to overcome inherent cohesion through controlled dispersion and encapsulation of microdroplets. Hybridization chain reaction (HCR)‐amplified catalytic process couples with ascorbic acid‐induced selective degradation of MnO ₂ shells, and exposed EGaIn‐LM microdroplets enable rapid formation of stimuli‐responsive hydrogel gates on a tin oxide substrate modified with high‐current‐gain 2D Bi ₂ O ₃ /CaIn ₂ S ₄ nanoarray. This critical mechanical barrier between the gate and electrolyte effectively redistributes internal electric fields and provides exceptional channel‐current regulation capabilities. This work establishes a pioneering framework for EGaIn‐LM hydrogel interface in OPECT devices, successfully converting molecular recognition events into interface reconfiguration signals. The OPECT achieves remarkable photocurrent modulation spanning three orders of magnitude and ultrasensitive detection of mycotoxin zearalenone with a detection limit of 2.6 fg mL ⁻¹ .