Makerspace microfabrication of a stainless steel 3D microneedle electrode array (3D MEA) on a glass substrate for simultaneous optical and electrical probing of electrogenic cells

Microfabrication and assembly of a Three-Dimensional Microneedle Electrode Array (3D MEA) based on a glass-stainless steel platform is demonstrated involving the utilization of non-traditional "Makerspace Microfabrication" techniques featuring cost-effective, rapid fabrication and an assorted biocompatible material palette. The stainless steel microneedle electrode array was realized by planar laser micromachining and out-of-plane transitioning to have a 3D configuration with perpendicular transition angles. The 3D MEA chip is bonded onto a glass die with metal traces routed to the periphery of the chip for electrical interfacing. Confined precision drop casting (CPDC) of PDMS is used to define an insulation layer and realize the 3D microelectrodes. The use of glass as a substrate offers optical clarity allowing for simultaneous optical and electrical probing of electrogenic cells. Additionally, an interconnect using 3D printing and conductive ink casting has been developed which allows metal traces on the glass chip to be transitioned to the bottomside of the device for interfacing with commercial data acquisition/analysis equipment. The 3D MEAs demonstrate an average impedance/phase of ∼13.3 kΩ/-12.1° at 1 kHz respectively, and an average 4.2 μV noise. Lastly, electrophysiological activity from an immortal cardiomyocyte cell line was recorded using the 3D MEA demonstrating end to end device development.