Acoustic focusing with engineered node locations for high-performance microfluidic particle separation.
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).
Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA, 94550 USA. shusteff1@llnl.gov.
Erika J
EJ
Fong
Amanda C
AC
Johnston
Timothy
T
Notton
Seung-Yong
SY
Jung
Klint A
KA
Rose
Leor S
LS
Weinberger
Maxim
M
Shusteff
D000162:Acoustics; D000818:Animals; D057005:Bioengineering / Q000379:methods; D002522:Chlorocebus aethiops; D003716:Dengue Virus / Q000302:isolation & purification*; D046210:Microfluidic Analytical Techniques / Q000379:methods* / Q000592:standards; D008863:Microspheres; D010316:Particle Size; D014709:Vero Cells