A Fully Lithography‐Free Fabrication Strategy for Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) are promising bioelectronic devices that leverage volumetric amplification for highly sensitive biosensing, but their fabrication typically relies on complex and costly cleanroom‐based photolithography. Despite recent efforts toward printing‐based lithography‐free OECT fabrication, achieving high operational stability remains challenging. Here, we present a fully lithography‐free fabrication strategy that combines a laser‐cut polymer mask for electrode patterning with a sacrificial tape‐assisted process that enables patterning of spin‐coated channels and simultaneous passivation. Optimization of the coated channel area substantially improves channel resistance uniformity, reducing the coefficient of variation to as low as 12%. The fabricated devices retain 97% of their initial drain current ( I D ) after 50 consecutive transfer cycles and 98% after 900 cycles of pulsed‐gate operation, demonstrating high operational stability. Furthermore, we demonstrate the applicability of this fabrication strategy to OECT‐based biosensors through glucose and potassium ion sensing. This work provides a simple route to OECT fabrication, enabling rapid prototyping and broader adoption of OECT technologies beyond specialized cleanroom facilities.