Reactive Sputtered Silicon Nitride as an Alternative Passivation Layer for Microelectrode Arrays in Sensitive...

Area of Science:

• Biomedical Engineering
• Materials Science
• Cell Biology

Background:

• Microelectrode arrays (MEAs) are crucial for real-time, noninvasive cell behavior studies.
• The passivation layer in MEAs, often SU-8, has limitations in optical transmission, cell support, and microfluidic integration.
• SU-8's limitations hinder advanced applications in polymer-based lab-on-chip systems.

Purpose of the Study:

• To establish and evaluate silicon nitride (SiN) as an alternative passivation layer for MEAs.
• To compare the surface characteristics, biocompatibility, and electrical insulation of SiN with SU-8.
• To assess the impact of SiN passivation on impedance spectroscopy-based cell monitoring.

Main Methods:

• Silicon nitride (SiN) passivation was developed using physical vapor deposition (PVD).
• Surface properties, biocompatibility, and electrical insulation were characterized and compared to SU-8.
• Adherent cell models (HEK-293 A and MCF-7) were cultured and measured on MEAs with SiN passivation using impedance spectroscopy.
• Microfluidic structures made of PEGDA and PDMS were bonded to the SiN layer.

Main Results:

• SiN demonstrated overall suitability as a passivation layer for MEAs.
• Cell signal detection was comparable or slightly decreased on smaller electrodes (<50 μm) compared to SU-8, depending on the cell line.
• A significantly higher cell signal was observed on microelectrodes larger than 50 μm with SiN passivation.
• SiN exhibited excellent compatibility for bonding with PEGDA and PDMS microfluidic components without leakage.

Conclusions:

• Silicon nitride (SiN) is a viable alternative to SU-8 for MEA passivation.
• SiN enhances cell signal detection on larger microelectrodes, improving impedimetric analysis.
• The material's compatibility with microfluidic systems makes it suitable for advanced lab-on-chip applications.