Digital microfluidics: an emerging sample preparation platform for mass spectrometry

Mass spectrometry (MS) has become an indispensable tool for laboratory science, but a drawback is the laborious sample processing required before MS analysis. Digital microfluidics (DMF), a microscale liquid handling technique characterized by the manipulation of fluid droplets on open electrode arrays, presents a potential solution to this problem. In DMF, discrete droplets can be made to merge, mix, split, and dispense from reservoirs. Since droplets are manipulated individually and act as discrete microreactors, DMF is well suited for microscale sample processing. Coupling the versatility of MS analysis with DMF sample handling has been beneficial for a number of DMF-based applications, including proteomics, chemical synthesis, and clinical diagnostics. In this review, we provide a summary of efforts to integrate these two technologies, focusing on examples of both off-line and in-line MS analysis for DMF sample processing.