Electrically actuated, pressure-driven liquid chromatography separations in microfabricated devices

Abstract

Electrolysis-based micropumps integrated with microfluidic channels in micromachined glass substrates are presented. Photolithography combined with wet chemical etching and thermal bonding enabled the fabrication of multi-layer devices containing electrically actuated micropumps interfaced with sample and mobile phase reservoirs. A stationary phase was deposited on the microchannel walls by coating with 10% (w/w) chlorodimethyloctadecylsilane in toluene. Pressure-balanced injection was implemented by controlling the electrolysis time and voltage applied in the two independent micropumps. Current fluctuations in the micropumps due to the stochastic formation of bubbles on the electrode surfaces were determined to be the main cause of variation between separations. On-chip electrochemical pumping enabled the loading of pL samples with no dead volume between injection and separation. A mobile phase composed of 70% acetonitrile and 30% 50 mM acetate buffer (pH 5.45) was used for the chromatographic separation of three fluorescently labeled amino acids in <40 s with an efficiency of >3000 theoretical plates in a 2.5 cm-long channel. Our results demonstrate the potential of electrochemical micropumps integrated with microchannels to perform rapid chromatographic separations in a microfabricated platform. Importantly, these devices represent a significant step toward the development of miniaturized and fully integrated liquid chromatography systems.

Smartphone-interfaced lab-on-a-chip devices for field-deployable enzyme-linked immunosorbent assay

“…[26][27][28][29] The material of the electrodes is often platinum and the electrolyte is commonly water as its molecules break down to oxygen and hydrogen gases. 28,[30][31][32][33] The advantage of using water-based gas generating micropumps is biocompatibility, which allows its implementation in various biomedical applications including blood cell analysis, 29,34 glucose sensors, 35 and intraocular drug delivery. [36][37][38] Non-liquid phase bubble generation has been reported using manganese dioxide (MnO 2 ) powder to react with hydrogen peroxide [39][40][41] and sodium polyacrylate-based hydrogel containing 99 wt.…”

Liquid chromatography on chip

“…This mechanism requires low voltages, builds up pressures around 15-20 bar, and can induce hydrodynamic flow rates in the range of 80 nL/min through an open-tubular column [68] or a packed bed [69]. In the most accomplished reduction of dead volume and delay volume, Xie et al [69] presented an electrochemical pump with two 20 mL reservoirs linked to a 1.5 nL static mixer to perform a mobile phase gradient through a 1.2 cm-long packed bed.…”

Integrated Multiprocess Microfluidic Systems for Automating Analysis

“…For instance, microfluidic devices offer low sample and reagent consumption3 (which is critical for expensive pharmaceutical characterization or trace samples), small dead volume,4 fast mixing,5–7 rapid analysis speed,8 high throughput,9 and valveless flow control 10. Consequently, these advantages of microfabricated devices have been exploited widely in bioanalysis, and reviews cover areas such as protein separation,2, 11 cell analysis,12–14 genomics,15, 16 and biomarker assays 17, 18.…”