Digital microfluidics has become a popular tool for biochemical and biomedical applications. However, its current format is restricted to actuation of droplets on a single plane. Here, we introduce a new method for fluid handling on flexible devices, which we have termed all-terrain droplet actuation (ATDA). We show that ATDA can be used to manipulate droplets across a wide range of geometries, including inclined, declined, vertical, twisted, and upside-down architectures. These new geometries enable flexible, straightforward integration of distinct physicochemical environments on monolithic devices. To illustrate this capacity, we developed temperature- and oxygen-sensitive colorimetric sensors, as well as an automated method for selective enrichment of DNA from a heterogeneous mixture. We anticipate that ATDA will be a useful new tool in the growing trend toward laboratory miniaturization.

Proteomics has emerged as the next great scientific challenge in the post-genome era. But even the most basic form of proteomics, proteome profiling, i.e., identifying all of the proteins expressed in a given sample, has proven to be a demanding task. The proteome presents unique analytical challenges, including significant molecular diversity, an extremely wide concentration range, and a tendency to adsorb to solid surfaces. Microfluidics has been touted as being a useful tool for developing new methods to solve complex analytical challenges, and, as such, seems a natural fit for application to proteome profiling. In this review, we summarize the recent progress in the field of microfluidics in four key areas related to this application: chemical processing, sample preconcentration and cleanup, chemical separations, and interfaces with mass spectrometry. We identify the bright spots and challenges for the marriage of microfluidics and proteomics, and speculate on the outlook for progress.

Clinical proteomics has emerged as an important new discipline, promising the discovery of biomarkers that will be useful for early diagnosis and prognosis of disease. While clinical proteomic methods vary widely, a common characteristic is the need for (i) extraction of proteins from extremely heterogeneous fluids (i.e. serum, whole blood, etc.) and (ii) extensive biochemical processing prior to analysis. Here, we report a new digital microfluidics (DMF) based method integrating several processing steps used in clinical proteomics. This includes protein extraction, resolubilization, reduction, alkylation and enzymatic digestion. Digital microfluidics is a microscale fluid-handling technique in which nanoliter-microliter sized droplets are manipulated on an open surface. Droplets are positioned on top of an array of electrodes that are coated by a dielectric layer -when an electrical potential is applied to the droplet, charges accumulate on either side of the dielectric. The charges serve as electrostatic handles that can be used to control droplet position, and by biasing a sequence of electrodes in series, droplets can be made to dispense, move, merge, mix, and split on the surface. Therefore, DMF is a natural fit for carrying rapid, sequential, multistep, miniaturized automated biochemical assays. This represents a significant advance over conventional methods (relying on manual pipetting or robots), and has the potential to be a useful new tool in clinical proteomics. . Leave the substrates in Piranha solution for 10 min with frequent agitation. 2. After rinsing in deionized (DI) water and drying the substrates with N2 gas, place the substrates inside the electron beam chamber for chromium deposition (thickness of 250 nm). 3. To dehydrate the chromium-coated substrate, rinse in isopropanol and then bake on a hot plate for 5 min at 115°C. 4. Dry the substrates and prime with hexamethyldisilazane (HMDS) by spin-coating (30 s, 3000 rpm). Spin-coat again (using identical parameters) with Shipley S1811 photoresist. 5. Pre-bake the substrate on a hot-plate (100°C, 2 min), then pattern the photoresist by exposure to ultraviolet (UV) irradiation for 5 s through a photomask. 6. Develop the UV-exposed substrates in Shipley MF 321 developer for 3 min and wash in DI water. Post-bake on a hot-plate at 100°C for 1 min. 7. Etch the exposed chromium by immersing in chromium etchant for 30 s. Rinse in DI water, then immerse in AZ300T stripper for 10 min to remove the remaining photoresist. Rinse in DI water and dry with N2 gas. 8. Deposit 2-5 μm Parylene-C (an insulating polymer) by chemical vapor deposition onto a substrate bearing patterned chromium. Deposit 50 nm of Teflon-AF (to make the surface hydrophobic) by spin-coating a solution (1% wt/wt in Fluorinert FC-40) at 2000 rpm for 60 s. Post-bake on a hot-plate (160°C, 10 min). 9. To form the top plate, coat an un-patterned indium tin oxide (ITO) glass substrates 50 nm Teflon-AF, as above. 10. Post-bake both substrates on a hot-plate (160°C, 10 min).1. In digita...

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We report a new method for fabricating nanospray ionization tips for MS, formed from glass substrates and the inert polymer, parylene-C. Using a single photolithography step, the emitters are formed contiguously with microchannels, such that no dead volumes are observed. In addition, because the devices are very thin (approximately 0.3 mm) and the tips are formed at rectangular corners, the Taylor cone volumes are small, which makes the method attractive for future integration with microfluidic separations. Device performance was demonstrated by evaluating diverse analytes, ranging from synthetic polymers, to peptides, to nucleic acids. For all analytes, performance was similar to that of conventional emitters (pulled-glass capillaries and the Agilent HPLC Chip) with the advantage of rapid, batch fabrication of identical devices.