INTEGRATING ORGANIC ELECTROCHEMICAL TRANSISTORS WITH 3D-PRINTED OBJECTS

Abstract

Printed electronics provide an additive manufacturing approach for fabricating electronic devices by depositing functional materials such as conductive, semiconductive, and dielectric inks onto various substrates. Unlike traditional subtractive methods, printing techniques reduce material waste and simplify the fabrication process. However, achieving high-performance printed devices remains challenging, particularly in terms of conductivity and resolution. This challenge is amplified when integrating printed electronics with three-dimensional (3D) printed objects, where surface roughness and material compatibility affect device functionality. This dissertation studies the integration of organic electrochemical transistors (OECTs) with 3D-printed objects, focusing on three key aspects: improving the surface quality of fused deposition modeling (FDM) substrates, dispense printing of silver electrodes on both hydrophilic and hydrophobic substrates, and the fabrication and characterization of fully printed high-performance OECTs. Surface ironing is studied as a method to reduce the roughness of FDM-printed substrates, demonstrating a reduction of more than 90% in absolute surface roughness. The study of dispense-printed silver electrodes on hydrophobic and hydrophilic surfaces highlights the impact of substrate properties on printing consistency and electrode formation. Fully printed OECTs are fabricated using dispense-printed silver electrodes and inkjet-printed PEDOT:PSS semiconducting layers. Electrical characterization shows that these transistors achieve a peak transconductance (gm) of 98.2 mS, the highest reported for a fully printed OECT. This high gm is attributed to the low-resistance, thick electrodes enabled by dispense printing, ensuring enhanced charge injection and reduced contact resistance. The devices also exhibit stable operation over multiple measurement cycles, demonstrating repeatability and robustness. The primary goal of this work is the embedding of high-performance OECTs within 3D-printed objects, enabling the direct integration of electronics into complex geometries. By demonstrating the feasibility of fully printed OECTs on smoothed 3D-printed surfaces, this research establishes a foundation for advancing printed electronic systems. The findings open possibilities for bioelectronics, wearable sensors, flexible circuits, and integrated functional devices, where seamless integration of electronics with non-planar structures is critical for next-generation applications.