Fabrication of microfluidic devices by excimer laser ablation under different atmospheres may provide variations in polymer microchannel surface characteristics. The surface chemistry and electroosmotic (EO) mobility of polymer microchannels laser ablated under different atmospheres were studied by X-ray photoelectron spectroscopy and current monitoring mobility measurements, respectively. The ablated surfaces of PMMA were very similar to the native material, regardless of ablation atmospheres due to the negligible absorption of 248 nm light by that polymer. The substrates studied that exhibit nonnegligible absorption at this energy, namely poly(ethylene terephthalate glycol) poly(vinyl chloride), and poly (carbonate), showed significant changes in surface chemistry and EO mobility when the ablation atmospheres were varied. Ablation of these three polymer substrates in nitrogen or argon resulted in low EO mobilities, with a loss of the well-defined chemical structures of the native surfaces, while ablation under oxygen yielded surfaces that retained native chemical structures and supported higher EO mobilities.
Citation: Analytical Chemistry
Issue: No. 4
Pub Type: Journals
electroosmotic flow, laser ablation, microfluidics, PC, PETG, PMMA, PVC, surface chemistry