Integrated microfluidics based on multi-layered SU-8 for mass spectrometry analysis

Abstract

We present a design for integrated lab-on-chip microsystems dedicated to mass spectrometry analysis based on the fabrication of watertight microchannels for the circulation of liquids. In this paper, we demonstrate how to fabricate complete polymer microchannels using the negative photoresist SU-8 which has the advantage of being compatible with protein analysis by mass spectrometry. Our method of fabrication requires novel technological steps involving SU-8 multi-layer processing, improved SU-8 adhesion and the use of SU-8 wafer bonding for the watertight closing of the microchannels with a Pyrex wafer. This technique also encompasses the design of various microfluidic elements such as tapered recesses for the housing of capillary tubes allowing the connection of the channels to external systems. Following this, the capillary tubes were used to test the hydrodynamic behaviour of the channels and consequently the efficiency of our technological process in achieving fully watertight structures within our flow rate and pressure specifications.

SU‐8 as a structural material for labs‐on‐chips and microelectromechanical systems

“…Typical processes involve bonding temperatures between 50 and 707C. Very thin layers of uncross-linked SU-8 were used as adhesive to avoid a filling of the gap [80][81][82]. A challenge in this technique is the patterning of the uncross-linked layer.…”

“…This is a critical point in microfluidics where chips with large surfaces are often required. A common trick is to design channels with thin walls on the order of few hundreds microns [80]. Pillars are then necessary to support the capping layer.…”

Multistep Synthesis on SU-8: Combining Microfabrication and Solid-Phase Chemistry on a Single Material

“…The selection of the sacrificial layer was based on good adhesion properties towards SU-8, ease of handling and simplicity of etching process. [17][18][19][20] The last variable is critical and requires that the sacrificial layer is efficiently and rapidly removed, releasing the SU-8 particles into suspension without compromising the presence of residual surface epoxy groups to be used for functionalization.…”

Recent developments in detection for microfluidic systems

“…Arscott and Le Gac's group used SU-8 as their production material, which is well compatible with the analysis of proteins. Based on their previous work, they were later able to build a multilayered microfluidic system [86].…”