Abstract

Digital Microfluidic Sample Processing for Separations and Mass Spectrometry

Chang Liu, Fellow Researcher , The University of Toronto

Digital microfluidics (DMF) is an emerging liquid-handling technology that manipulates droplets independently on an open array of electrodes. Through the application of a series of potentials to these electrodes, picoliter-to-microliter-sized droplets, each serving as an isolated vessel for chemical processes, can be made to move, merge, split, and disperse from reservoirs with automated fashion. The absolute control over samples and reagents, and the convenient solvent exchange and product collection make DMF an attractive technique for sample processing. 

We used testosterone analysis from dried urine spots as an example to demonstrate the fast sample processing on digital microfluidic platforms. On a DMF device, the sample preparation was carried out in microliter-sized droplets. The small sample volume and the unique shape of the droplet allow the fast reaction kinetics due to the enhanced reagent mixing. 

 In another study, we developed a novel approach for the direct in-line interfacing of DMF with LC-MS. By prefilling a water droplet in the access hole drilled through the top DMF plate, the sample droplet can be successfully withdrawn from the DMF device. The needle of the autosampler could then be moved to this access hole to load the sample solution into the LC/MS system directly.