Our research can be divided into the following topics. Click below to learn more.

DMF Theory & Improvements Optoelectronic Tweezers DMF for Cell Culture & Analysis DMF for Clinical Applications Digital Extraction Techniques Digital Chemical Reactors

Digital Microfluidic Theory and Improvements


"Digital microfluidics" is a term used to describe the fluid-handling technique in which discrete liquid droplets are manipulated electromechanically across an array of electrodes coated with a hydrophobic insulator. For new users, we recently developed an open-source digital microfluidic control system, called DropBot (see the DropBot archive for schematics, downloads, instructions, and more). Additionally, we have written several review articles describing digital microfluidics (see articles in Science, ABC, Adv. Mat., COCB, or ARAC), and have worked to develop a variety of method improvements, tackling issues including biofouling, device geometry limitations, electronic control systems, and reliable dispensing. Papers describing our efforts in these areas are listed below.


Optoelectronic Tweezers


"Optoelectronic Tweezers" (OET) is a manipulation tool that is related to digital microfluidics (DMF). In both techniques, electric potentials are applied to a series of electrodes to allow for the manipulation of fluids and particles. A key difference is – in conventional DMF, the electrodes are permanent, while in OET, the electrodes are ‘virtual’ – that is, ‘virtual electrodes’ are defined by the projection of light onto an unpatterned photoconductive material. In effect, this allows for the generation of electrodes with arbitrary size and position, that can be moved in time by projecting a series of moving light patterns onto the device. Papers describing our work with OET are listed below, and a short movie illustrating our OET-driven microrobot can be viewed here. For more on OET, see our recent review article in Chemical Society Reviews.


Digital Microfluidics for Cell Culture and Analysis


In vitro cell culture and analysis is omnipresent in modern biology labs, but this comes at a cost, with world-wide activities requiring an annual expenditure of billions of dollars and hundreds of thousands of laboratory hours. Our group was the first to explore the compatibility of digital microfluidics with mammalian cell culture to automate the process and reduce reagent consumption; papers in this area are listed below. For more, see our recent review paper describing the use of DMF for cell culture and analysis.


Digital Microfluidics for Clinical Applications


Many applications in the clinical laboratory require the use of complex, heterogeneous samples such as ~mm-sized tissue sections or dried blood spots (DBSs) on filter paper. Digital microfluidics confers unique advantages for such applications, such as the capacity to work with meso-scale reagent volumes (nL – µL), and compatibility with solid samples (i.e., no chance of clogging). We have recently begun to exploit these properties to develop integrated “sample-to-answer” systems for clinical analysis. Papers in this area are listed below.


Digital Extraction Techniques


Most real-world chemical analysis applications begin with a complex sample that contains a mixture of many constituents (e.g., serum, pond water, cell lysate, etc.). Complex samples are often impossible to analyze without extraction (or "cleanup") to simplify the sample. Digital microfluidics is proving to be a powerful technology for extraction, which can include non-specific methods (e.g., reversed-phase solid extraction or liquid-liquid extraction) and specific methods (e.g., using immunospecificity to isolate desirable analytes). Papers describing our efforts in this area are listed below.


Digital Chemical Reactors


Chemists have long been interested in miniaturizing chemical reactions to take advantage of favorable scaling of diffusion and heat exchange. Most efforts to miniaturize chemical reactions have relied on networks of enclosed microchannels. Such systems are not an ideal match for this application because of clogging of solid reagents and precipitates, complex plumbing issues, and material incompatibilities. Digital microfluidics represents a potential solution to these problems. We are working to develop digital liquid reactors for a variety of applications including multiplexed chemical synthesis and enzyme assays. Papers describing these efforts are listed below.