Glass/SU‐8 microchip for electrokinetic applications

Abstract

Glass/SU-8 microchip for electrokinetic applicationsIn this communication, we describe the fabrication and electric characterization of a hybrid glass/SU-8 microchannels for high-performance electrokinetic applications. The bonding process employed SU-8 film as intermediate layer with reduced baking times; all the procedure took less than 50 min (only about 10 min disregarding the cleaning and dehydration steps). Additionally, further steps to improve the adhesion of the substrate to the SU-8 were not needed. The developed configuration aggregates the advantages of both substrates, including (i) simple fabrication techniques; (ii) high compatibility for integration of microelectromechanical, optical, and electrochemical components (SU-8); (iii) high and stable electroosmotic mobility ( EO ); and (iv) satisfactory heat dissipation capacity (glass). Electroosmotic mobilities were measured as a function of the pH using the current monitoring method, whereas the heat dissipation capacity was investigated through Ohm's law plots for both glass and glass/SU-8 microchips. The measured EO values were similar for both microdevices, with mobilities of the order of 4.0-4.5 × 10 −4 cm 2 V −1 cm −1 at 4-12 pH range using phosphate buffer (10 and 20 mmol/L). The heat dissipation assays were carried out in microchannels filled with 20 mmol/L phosphate buffer. A considerable Joule heating was observed only at electric field strengths greater than 580 V cm −1 in hybrid glass/SU-8 microdevices, representing a substantial increase of 48% when compared to all SU-8 microdevices. Keywords:Bonding / Microfabrication / Photoresist DOI 10.1002/elps.201300167Additional supporting information may be found in the online version of this article at the publisher's web-siteMicrodevices integrating CE are a potential platform for microfluidics applications, especially for biomolecular assays in proteomics and metabolomics research. This platform provides simple, effective, small-in-volume, and high-resolution separations. Glass is the most used material in the fabrication of CE chips [1]. Vitreous substrates carry important advantages, including (i) optical transparency, (ii) chemical inertia, (iii) high and stable electroosmotic mobility ( EO ), and (iv) good thermal conductivity ( = 1.5 W mK −1 ) [2]. The latter allows the application of high electric field strengths (>600 V cm −1 ) without formation of temperature gradienta negligible Joule heating, contributing for fast separations.

Sacrificial adhesive bonding: a powerful method for fabrication of glass microchips

“…In general, adhesive bonding is attained only after curing (polymerization) of the adhesive intermediate 26 . In this case, highly aggressive solvents would be required for the development step in SAB, damaging the bonding itself and any functional components integrated in the microfluidic device.…”

“…Cure of the SU-8 requires two sequential steps: (1) UV exposure at 365 nm for formation of the photoactivator and (2) post-exposure bake (PEB) to allow the polymerization of SU-8 monomers 26 27 . The chemical structures and reactions involved in this process are depicted in Fig.…”

Mass transfer of a neutral solute in porous microchannel under streaming potential

“…The analysis of transport phenomena in microfluidic systems has gained considerable interest in the past couple of years . Development of microfluidic devices has found intensive applications in the field of bioanalysis , bioseparation , microchips , sensors , controlled drug delivery and drug discovery , microseparation systems separating biomolecules , ions , neutral solutes , etc., owing to their high surface‐to‐volume ratio and complex fluid flow associated with electrokinetic effects.…”

Enhancement of Electrical and Mechanical Properties of SU-8 Photocrosslinked Coatings Containing Polypyrrole-graphene Oxide Nanoparticles

“…UV-curing process SU-8 photoresist is a mixture of epoxy novolac resin, a solvent (either γ-butyrolactone or cyclopentane) and a photoacid generator (a triarylsulfonium hexafluroantimonate salt). Photo curing of the SU-8 photoresist occurred in two sequential steps: (1) UV exposure for formation of the photoactivator and (2) post-exposure bake (PEB) to allow the polymerization of SU-8 monomers [19,20]. The chemical structures and reactions involved in this process are presented in Fig.…”