Sacrificial Layer Technique for Releasing Metallized Multilayer SU-8 Devices

Area of Science:

• Microfabrication
• Materials Science
• Nanotechnology

Background:

• SU-8 based devices are crucial for point-of-care (POC), micro total analysis systems (µTAS), and Lab-on-Chip (LOC) technologies due to low fabrication costs.
• Fabricating free-standing, suspended devices requires a sacrificial layer for release from carrier wafers.
• Existing inorganic and organic sacrificial materials are inadequate for multilayer SU-8 device fabrication and release.

Purpose of the Study:

• To introduce and validate photoresist AZ 15nXT as a novel sacrificial layer material for SU-8 based microdevices.
• To develop and demonstrate methods for cross-linking AZ 15nXT to create stable sacrificial layers.
• To establish effective sacrificial release routes for multilayer free-standing SU-8 devices.

Main Methods:

• Investigated two distinct cross-linking methods for AZ 15nXT to ensure stability during SU-8 processing.
• Developed and tested three different sacrificial release strategies for multilayer SU-8 devices.
• Fabricated a three-layer free-standing microfluidic electrospray ionization (ESI) chip as a proof-of-concept.

Main Results:

• AZ 15nXT demonstrated stability throughout the SU-8 processing steps, enabling multilayer device fabrication.
• Successful sacrificial release of multilayer SU-8 devices was achieved using the developed methods.
• Demonstrated the fabrication of a functional three-layer free-standing microfluidic ESI chip and a multilayer device with integrated electrodes.

Conclusions:

• Photoresist AZ 15nXT is a suitable and effective sacrificial material for fabricating complex, free-standing multilayer SU-8 devices.
• The developed cross-linking and release processes facilitate the production of cost-effective and disposable microdevices for POC and LOC applications.
• This advancement supports the broader adoption of SU-8 based microfluidic technologies by overcoming previous fabrication limitations.