3D laser Nanoprinting of Ultra‐High Conductivity Organic Bioelectronics

ABSTRACT 3D printing of conducting polymers has garnered increasing interests owing to their emerging potentials in nanoelectronics, nanophotonics and bioelectronics. Even though direct laser printing techniques surpassing conventional inkjet printing offer nanoscale resolution and advanced 3D capability, disordered molecular main chain, insulating side chain and irregular phase separation impose additional energy barriers to charge transport kinetics in photocurable polymer framework, thereby compromising overall conductivity performance of as‐fabricated devices. Here, we develop a novel poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hydrogel photoresin for realizing highly conductive organic 3D nanostructures by using multiphoton direct laser printing technique. High pulse energy of the polarized femtosecond laser has been shown to induce the arrangement of the PEDOT:PSS nanofibrils and side chains of PSS detaching from PEDOT, which enables fabricated nanowires with a record‐high conductivity of approximately 1010 S/cm and a deep sub‐diffraction limit feature size of 78 nm. The facile printability allows sophisticated 3D bioelectronics to be in‐situ fabricated and integrated with microfluidic chips, enabling precise sensing water contents. Leveraging its biocompatibility, we further demonstrate 3D bioelectronic sensors for real‐time monitoring of ethanol yields throughout the yeast fermentation process.