Fabrication of Planar Microelectrode Array Using Laser-Patterned ITO and SU-8

Abstract

For several decades, microelectrode array (MEA) has been a powerful tool for in vitro neural electrophysiology because it provides a unique approach for monitoring the activity of a number of neurons over time. Due to the various applications of MEAs with different types of cells and tissues, there is an increasing need to customize the electrode designs. However, the fabrication of conventional MEAs requires several microfabrication procedures of deposition, etching, and photolithography. In this study, we proposed a simple fabrication method with a laser-patterned indium tin oxide (ITO) conductor and SU-8 photoresist insulation. Unlike in a conventional metal patterning process, only the outlines of ITO conductors are ablated by laser without removing background ITO. Insulation is achieved simply via SU-8 photolithography. The electrode sites are electroplated with iridium oxide (IrOX) to improve the electrochemical properties. The fabricated MEAs are electrochemically characterized and the stability of insulation is also confirmed by impedance monitoring for three weeks. Dissociated neurons of rat hippocampi are cultured on MEAs to verify the biocompatibility and the capacity for extracellular neural recording. The electrochemical and electrophysiological results with the fabricated MEAs are similar to those from conventional SiNX-insulated MEAs. Therefore, the proposed MEA with laser-patterned ITO and SU-8 is cost-effective and equivalently feasible compared with the conventional MEAs fabricated using thin-film microfabrication techniques.

Micro-Sized pH Sensors Based on Scanning Electrochemical Probe Microscopy

“…These properties, along with their fast response, extended lifetimes, and stability in a variety of atmospheres, make them suitable for a variety of applications [16]. They are usually easily deposited on different substrates, which makes them good candidates for applications in novel microelectrode arrays [17,18].…”

Silicon optrode array with monolithically integrated SU-8 waveguide and single LED light source

“…The silver/silver chloride (Ag/AgCl) (MF-2052, Bioanalytical Systems, Inc., West Lafayette, IN, USA) reference electrode and platinum counter electrode (CHI115, CH Instruments, Inc., Bee Cave, TX, USA) are used in the IrO x electroplating bath. During the electroplating process, the triangular pulses reduce the impedance and improve mechanical properties, and the rectangular pulses increase the charge storage capacitance [31,32]. Figure 4(e) shows the impedance drop after IrO x electroplating, and figure 4(f) shows IrO x electroplated on the Au electrodes.…”

Investigating electrochemical deposition of gold on commercial off-the-shelf 3-D printing materials towards developing sensing applications

“…6,7 To reduce fabrication costs, Jeong et al produced a lowcost microelectrode array (MEA) which used a laser-patterned indium tin oxide (ITO) substrate and SU-8 photoresist as insulation using photolithography. 8 However, this method required the ITO to be deposited via sputtering by UID KOREA, limiting accessibility. 8 Previously, our group fabricated an electrode chip using a combination of 3-dimensional (3-D) printing to create shadow masks with physical vapour deposition (PVD) to deposit gold onto glass slides.…”

“… 8 However, this method required the ITO to be deposited via sputtering by UID KOREA, limiting accessibility. 8 Previously, our group fabricated an electrode chip using a combination of 3-dimensional (3-D) printing to create shadow masks with physical vapour deposition (PVD) to deposit gold onto glass slides. 9 Even though 3-D printed shadow masks avoided photolithography, the PVD process still requires access to a clean room, and results in considerable gold waste.…”