Articles by Erika J. Fong in JoVE
A Microfluidic Platform for Precision Small-volume Sample Processing and Its Use to Size Separate Biological Particles with an Acoustic Microdevice Erika J. Fong1,2, Chao Huang1, Julie Hamilton1, William J. Benett1, Mihail Bora1, Alison Burklund1, Thomas R. Metz1, Maxim Shusteff1 1Materials Engineering Division, Lawrence Livermore National Laboratory, 2Department of Biomedical Engineering, Boston University This protocol describes a system architecture for performing automated small volume (0.15–1.5 ml) particle separations using a microfluidic device, and discusses methods to optimize acoustofluidic device performance and operation.
Other articles by Erika J. Fong on PubMed
Decoupling Directed and Passive Motion in Dynamic Systems: Particle Tracking Microrheology of Sputum Annals of Biomedical Engineering. Apr, 2013 | Pubmed ID: 23271563 Probing the physical properties of heterogeneous materials is essential to understand the structure, function and dynamics of complex fluids including cells, mucus, and polymer solutions. Particle tracking microrheology is a useful method to passively probe viscoelastic properties on micron length scales by tracking the thermal motion of beads embedded in the sample. However, errors associated with active motion have limited the implementation to dynamic systems. We present a simple method to decouple active and Brownian motion, enabling particle tracking to be applied to fluctuating heterogeneous systems. We use the movement perpendicular to the major axis of motion in time to calculate rheological properties. Through simulated data we demonstrate that this method removes directed motion and performs equally well when there is no directed motion, with an average percent error of
Acoustic Focusing with Engineered Node Locations for High-performance Microfluidic Particle Separation The Analyst. Mar, 2014 | Pubmed ID: 24448925 Acoustofluidic devices for manipulating microparticles in fluids are appealing for biological sample processing due to their gentle and high-speed capability of sorting cell-scale objects. Such devices are generally limited to moving particles toward locations at integer fractions of the fluid channel width (1/2, 1/4, 1/6, etc.). In this work, we introduce a unique approach to acoustophoretic device design that overcomes this constraint, allowing us to design the particle focusing location anywhere within the microchannel. This is achieved by fabricating a second fluid channel in parallel with the sample channel, separated from it by a thin silicon wall. The fluids in both channels participate to create the ultrasound resonance, while only one channel processes the sample, thus de-coupling the fluidic and acoustic boundaries. The wall placement and the relative widths of the adjacent channels define the particle focusing location. We investigate the operating characteristics of a range of these devices to determine the configurations that enable effective particle focusing and separation. The results show that a sufficiently thin wall negligibly affects focusing efficiency and location compared to a single channel without a wall, validating the success of this design approach without compromising separation performance. Using these principles to design and fabricate an optimized device configuration, we demonstrate high-efficiency focusing of microspheres, as well as separation of cell-free viruses from mammalian cells. These "transparent wall" acoustic devices are capable of over 90% extraction efficiency with 10 μm microspheres at 450 μL min(-1), and of separating cells (98% purity), from viral particles (70% purity) at 100 μL min(-1).