Atmospheric Photopolymerization of Acrylamide Enabled by Aqueous Glycerol Mixtures: Characterization and Application for Surface‐Based Microfluidics

Abstract

Polyacrylamide usually is the material of choice for electrophoretic separation in slab gels, capillaries, and microfluidic devices. So far its polymerization requires anaerobic environments because oxygen impurities inhibit or even terminate the polymerization reaction of acrylamide. Here, it is demonstrated that gel precursor solutions with glycerol contents above 20 vol% enable direct atmospheric photopolymerization of acrylamide with no need for sealing or degassing the solution in advance. The positive effect of glycerol on the polymerization reaction is proven by simulation‐validated electron paramagnetic resonance measurements. Nuclear magnetic resonance reveals that glycerol does not interfere with the reaction indicating that the observed enhancement in polymerization is owed to the low oxygen solubility of aqueous glycerol mixtures. Glycerol concentrations of >60 vol% in the gel precursor solution enable complete polymerization of volumes down to 5 nL within less than 5 s. This enables using liquid handling robots to fabricate channel‐free open microfluidic structures of solid polyacrylamide hydrogel in a low‐cost automated manner in a standard lab environment.

3D Printing Tannic Acid‐Based Gels via Digital Light Processing

“…The DLP of acrylate‐based monomers is based on radical‐mediated chain‐growth photopolymerization. [ 19 ] During the 3D printing, the photoinitiator is excited to produce free radicals, which open the double carbon bonds of acrylate groups on both the acrylamide and MBA to form crosslinked networks, thereby resulting in the solidification of the pre‐hydrogel solution into the corresponding solid pattern. [ 5 ] An entire 3D object can be obtained by the layer‐by‐layer solidifying process.…”

Paper‐based open microfluidic platform for protein electrophoresis and immunoprobing

“…We speculate that this was caused by the detrimental effect of oxygen on the polymerization process and the effective compartmentalization of the precursor solution within the pores of the CA membrane. Including benzophenone or glycerol into the precursor solution, which were reported to act as oxygen scavengers during acrylamide polymerization [16,40], did not improve the reproducibility of the polymerization process (data not shown). Linear polyacrylamide derivatives were also tested, but protein migration was rather poor in these matrices, owing to severe evaporation effects during electrophoresis (including premature current breakdown) as a consequence of using linear polymers that do not form hydrogels.…”