Multi‐material Electrohydrodynamic Printing of Bioelectronics with Sub‐Microscale 3D Gold Pillars for In Vitro Extra‐ and Intra‐Cellular Electrophysiological Recordings

Abstract Micro/nanoscale 3D bioelectrodes gain increasing interest for electrophysiological recording of electroactive cells. Although 3D printing has shown promise to flexibly fabricate 3D bioelectronics compared with conventional microfabrication, relatively‐low resolution limits the printed bioelectrode for high‐quality signal monitoring. Here, a novel multi‐material electrohydrodynamic printing (EHDP) strategy is proposed to fabricate bioelectronics with sub‐microscale 3D gold pillars for in vitro electrophysiological recordings. EHDP is employed to fabricate conductive circuits for signal transmission, which are passivated by polyimide via extrusion‐based printing. Laser‐assisted EHDP is developed to produce 3D gold pillars featuring a diameter of 0.64 ± 0.04 µm. The 3D gold pillars demonstrate stable conductivity under the cell‐culture environment. Living cells can conformally grow onto these sub‐microscale 3D pillars with a height below 5 µm, which facilitates the highly‐sensitive recording of extracellular signals with amplitudes <15 µV. The 3D pillars can apply electroporation currents to reversibly open the cellular membrane for intracellular recording, facilitating the measurement of subtle cellular electrophysiological activities. As a proof‐of‐concept demonstration, fully‐printed chips with multiple culturing chambers and sensing bioelectronics are fabricated for zone‐specific electrophysiological recording in drug testing. The proposed multi‐material EHDP strategy enables rapid prototyping of organ‐on‐a‐chip systems with 3D bioelectronics for high‐quality electrophysiological recordings.