A Feasibility Study of Customized and Fully Aerosol-Jet-Printed Micro-Electrode Arrays for In Vitro Application

The article proposes a fully printed microelectrode array (MEA) as a proof of concept for the feasibility of a customized and low-cost bioelectronic device. The target application is to promote the maturation of the cell culture by providing biophysical stimuli and evaluating the functionality of the bioengineered products, monitoring in real-time the electrogenic cell action potential. The MEA is entirely printed with aerosol jet printing (AJP) with a multilayer structure composed of an array of 16 electrodes. AJP fabrication was exploited as low-cost technique and easy and reliable possibility to print both insulated material and conductive polymer. Furthermore, the technique allows the realization of a customized electrode design according to specific neuronal network architecture. The chosen inks achieve the requirements for the intended use, in terms of high conductivity for electrodes, low conductivity for passivation layers, and biocompatibility for cell culture. Results from geometrical characterization showed an agreement with the design requirements. In particular, the first prototypes showed a thickness of the passivation layer of (33.4 ± 1.4) $\mu \text{m}$ and the silver conductive tracks with a thickness of (5.5 ± 0.6) $\mu \text{m}$ and a width of (68 ± 1.4) $\mu \text{m}$ . Electrochemical Impedance Spectroscopy established an impedance magnitude value significantly below compared with commercial MEA and inkjet printing MEA. The reusability and the stability of the sensor are demonstrated within two weeks. Overall, the results suggest the possibility to exploit the potential to print MEA onto platform, for in vitro cell culture and to integrate other types of biosensors.