Inkjet-Printed Rough Gold Microelectrode Arrays on Flexible Substrates for Neural Recording and Electrical Stimulation.

Microelectrode arrays (MEAs) are essential tools for recording and stimulating electrogenic tissues, but their fabrication typically depends on complex, costly, and mask-based cleanroom processes. While inkjet-printed MEAs have increasingly been explored as low-cost alternatives, most demonstrations have focused on cardiac cell recordings, with only a limited number of studies showing neuronal recordings. Furthermore, no work to date has demonstrated neuronal interfacing, combining single-unit recording with electrical stimulation, using inkjet-printed MEAs. Here, we investigate whether inkjet-printed MEAs enable both extracellular single-unit neuronal recording and reliable electrical stimulation. We fabricated gold microelectrodes on flexible foils via maskless inkjet-printing, insulated them with printed SU-8 (an epoxy-based dielectric), and characterized their morphology using scanning electron microscopy, atomic force microscopy, and profilometry, and their electrochemical behavior using impedance spectroscopy and cyclic voltammetry. The printed gold formed a rough nanoparticle-based morphology, resulting in an increased effective electrochemical surface area. This morphology enabled low electrode impedances and high charge injection during voltage-controlled stimulation. We assessed functional performance in ex vivo retinal tissue. The inkjet-printed MEAs enabled reliable single-unit recordings with signal-to-noise ratios comparable to cleanroom-fabricated commercial devices and cell activation upon electrical stimulation with biphasic pulses. The electrodes were reusable and noncytotoxic, verified via a standard cell viability assay. These results establish the first inkjet-printed microelectrodes capable of neuronal interfacing, demonstrating that printed MEAs can match the functional performance of conventional microfabricated devices. This work positions inkjet-printing as a scalable, easily adaptable, low-cost manufacturing technique for flexible MEAs with rough gold electrodes suitable for neurotechnology applications.