Michael G. Pollack

Bio: Michael G. Pollack is an academic researcher from Research Triangle Park. The author has contributed to research in topics: Digital microfluidics & Electrowetting. The author has an hindex of 52, co-authored 73 publications receiving 8885 citations. Previous affiliations of Michael G. Pollack include Duke University & United States Department of Energy Office of Science.

Droplet actuator for electroporation and transforming cells

Abstract: The invention provides a droplet actuator designed for performing electroporation on cells in droplets. The invention also provides method and systems for performing electroporation on cells in droplets on a droplet actuator.

Software automated genomic engineering (sage) enabled by electrowetting-on-dielectric digital microfluidics

Abstract: ABSTRA CT Software automated genomic engineering (SAGE) enables arbitrary genetic modification of bacteria on a fluidic platform that implements the multiplex automated genomic engineering (MAGE) process [1]. Electrowetting-ondielectric (EWD) digital microfluidics is well suited for SAGE because of its inherent reconfigurability, small reagent volumes, and parallel processing capability [2]. We report on the first demonstration of bulk cell transformation of E. coli by an electroporation device integrated with an EWD microfluidics system, which achieved up to 9.8% transformation efficiency (evaluated as the ratio of transformed cells to survived cells) while maintaining fluid transport capability. Toward the goal of enabling efficient MAGE cycling with real time feedback control, monitoring of cell recovery and growth was implemented via reflectance spectroscopy with a limit of detection of about 10 cells/ml. Furthermore, simulated MAGE cycles showed that bacteria remained viable for at least 90 cycles (27 days) on-chip.

Bubble formation techniques using physical or chemical features to retain a gas bubble within a droplet actuator

Abstract: The present invention is directed to a droplet actuator and methods of making and using the droplet actuator including one or more substrates configured to form a droplet operations gap and including a physical or chemical feature that may be provided at a predetermined locus within or exposed to the droplet operations gap and configured to retain a bubble in position within the droplet operations gap.

Automated electrowetting based droplet dispensing with good rei'roducibility

Abstract: Electrowetting based droplet on-chip dispensing is presented. On-chip reservoir and droplet formation channel are designed to facilitate droplet creation. The mechanism and conditions in which droplet can be formed are analyzed. The droplet volume variations are tested over a range of interfacial tension and number of pinch off electrode. The results show that droplet volume reproducibility is degraded significantly when liquid-oil interfacial tension is reduced. And droplet volume is a fimction of number of pinch off electrode and the timing of control sequence. Keyword: droplet dispensing, electrowetting, volume reproducibility

MEMS devices for detecting the presence of explosive material residues in mine fields

Abstract: We report on the development of MEMS devices for detecting explosive particles associated with anti-personnel mines Because of the affinity of explosive substances for surfaces and owing to the high partition coefficients of explosives in soils relative to water and air, we employ remote stimulation of the soil's surface with a high intensity, focused air ultrasonic beam whose energy can megasonically clean the target area of particles above a designed-for size We have fabricated a MEMS electrostatic transducer to test the concept Nanogram particle detection will occur by collecting particles on an array of temperature sensitive MEMS sensors and irradiating the particles with 3 - 5 micrometer wavelength infrared light Explosive particles will selectively absorb the infrared energy at approximately 1600 cm-1, decompose, and give off heat which can be detected Prototype explosive detectors have been fabricated which do not absorb energy in the peak absorption bands of the explosives, thus allowing for selective particle heating without heating the sensor device itself

Microfluidics: Fluid physics at the nanoliter scale

Abstract: Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

Engineering flows in small devices

Abstract: Microfluidic devices for manipulating fluids are widespread and finding uses in many scientific and industrial contexts. Their design often requires unusual geometries and the interplay of multiple physical effects such as pressure gradients, electrokinetics, and capillarity. These circumstances lead to interesting variants of well-studied fluid dynamical problems and some new fluid responses. We provide an overview of flows in microdevices with focus on electrokinetics, mixing and dispersion, and multiphase flows. We highlight topics important for the description of the fluid dynamics: driving forces, geometry, and the chemical characteristics of surfaces.

Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America

Abstract: It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

Electrowetting: from basics to applications

Abstract: Electrowetting has become one of the most widely used tools for manipulating tiny amounts of liquids on surfaces. Applications range from 'lab-on-a-chip' devices to adjustable lenses and new kinds of electronic displays. In the present article, we review the recent progress in this rapidly growing field including both fundamental and applied aspects. We compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high. We discuss in detail the origin of the electrostatic forces that induce both contact angle reduction and the motion of entire droplets. We examine the limitations of the electrowetting equation and present a variety of recent extensions to the theory that account for distortions of the liquid surface due to local electric fields, for the finite penetration depth of electric fields into the liquid, as well as for finite conductivity effects in the presence of AC voltage. The most prominent failure of the electrowetting equation, namely the saturation of the contact angle at high voltage, is discussed in a separate section. Recent work in this direction indicates that a variety of distinct physical effects?rather than a unique one?are responsible for the saturation phenomenon, depending on experimental details. In the presence of suitable electrode patterns or topographic structures on the substrate surface, variations of the contact angle can give rise not only to continuous changes of the droplet shape, but also to discontinuous morphological transitions between distinct liquid morphologies. The dynamics of electrowetting are discussed briefly. Finally, we give an overview of recent work aimed at commercial applications, in particular in the fields of adjustable lenses, display technology, fibre optics, and biotechnology-related microfluidic devices.