Microfabricated Organic Electrochemical Transistors Enabled by Printing and Laser Ablation

Abstract

Organic electrochemical transistors (OECTs) are key bioelectronic devices with applications in neuromorphics, sensing, and flexible electronics. OECTs made using biobased and biodegradable materials are emerging as a sustainable alternative to nondegradable plastic and metal-based electronics. Printing is the key technique used to fabricate these types of devices, enabling fabrication at room temperature and using benign solvents, such as water. However, printing techniques suffer from relatively low resolution (tens to hundreds of micrometers), far below the micrometer resolution achieved via conventional metal deposition and photolithography. Here, we present a high-throughput additive-subtractive microfabrication strategy for carbon-based flexible OECTs using biodegradable materials and room-temperature processing. Additive manufacturing of large features is achieved via extrusion printing of a graphene ink to fabricate electrode contacts on cellulose acetate (CA), which serves both as the substrate and as the insulation layer. Combined with femtosecond (fs) laser ablation, this approach enables micrometer-resolution patterning of freestanding OECTs with channel openings down to 1 μm and sheet resistance below 10 Ω/sq. By tuning laser parameters, we demonstrate both selective and simultaneous ablation strategies, enabling the fabrication of horizontal, vertical, and planar-gated OECTs, as well as complementary NOT gate inverters. Thermal degradation studies in air show that over 80% of the device mass decomposes below 360 °C, providing a low-energy route for device disposal and addressing the environmental impact of electronic waste. This approach offers a lithography-free pathway toward the rapid prototyping of high-resolution, sustainable organic electronics, combining circularity, process simplicity, and architectural versatility for next-generation bioelectronic applications.