We introduce a new method to construct microfluidic devices especially useful for bulk acoustic wave (BAW)-based manipulation of cells and microparticles. To obtain efficient acoustic focusing, BAW devices require materials that have high acoustic impedance mismatch relative to the medium in which the cells/microparticles are suspended and materials with a high-quality factor. To date, silicon and glass have been the materials of choice for BAW-based acoustofluidic channel fabrication. Silicon- and glass-based fabrication is typically performed in clean room facilities, generates hazardous waste, and can take several hours to complete the microfabrication. To address some of the drawbacks in fabricating conventional BAW devices, we explored a new approach by micromachining microfluidic channels in aluminum substrates. Additionally, we demonstrate plasma bonding of poly(dimethylsiloxane) (PDMS) onto micromachined aluminum substrates. Our goal was to achieve an approach that is both low cost and effective in BAW applications. To this end, we micromachined aluminum 6061 plates and enclosed the systems with a thin PDMS cover layer. These aluminum/PDMS hybrid microfluidic devices use inexpensive materials and are simply constructed outside a clean room environment. Moreover, these devices demonstrate effectiveness in BAW applications as demonstrated by efficient acoustic focusing of polystyrene microspheres, bovine red blood cells, and Jurkat cells and the generation of multiple focused streams in flow-through systems.
This is a preview of subscription content, log in to check access
MEP acknowledges funding for an Institutional Development Award from the National Institute of General Medical Sciences of the National Institutes of Health (NIH) under grant number P20GM103451, and SWG acknowledges funding from NIH (R21GM107805) and the National Science Foundation (1130140). SWG and MJC acknowledge funding from NIH (R44GM117649). The authors thank Snezna Rogelj and Danielle Turner in the Department of Biology at New Mexico Institute of Mining and Technology for providing Jurkat cell samples. The authors also thank Esequiel Lopez of Sandia Electro-Optics Corporation for his work and assistance with the machining of the devices and Paul Fuierer and Robert Calvo in the Materials Engineering Department at New Mexico Institute of Mining and Technology for their help with profilometer measurements. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy Office of Science by Los Alamos National Laboratory (contract DE-AC52-06NA25396) and Sandia National Laboratories (contract DE-NA-0003525). The authors thank Douglas V. Pete at the Center for Integrated Nanotechnologies, Albuquerque, for assistance in obtaining scanning electron microscopy images.
Compliance with ethical standards
Conflict of interest
GPG, TB, AW, and MEP declare that they have no competing interests. SWG and MJC declare a commercial interest in this technology as it is relevant to their commercial company, Eta Diagnostics, which is commercializing parallel acoustic flow cytometers.
Shi J, Huang H, Stratton Z, Huang Y, Huang TJ. Continuous particle separation in a microfluidic channel via standing surface acoustic waves (SSAW). Lab Chip. 2009;9(23):3354–9.CrossRefGoogle Scholar
Petersson F, Nilsson A, Holm C, Jonsson H, Laurell T. Continuous separation of lipid particles from erythrocytes by means of laminar flow and acoustic standing wave forces. Lab Chip. 2005;5(1):20–2.CrossRefGoogle Scholar
Hawkes JJ, Barber RW, Emerson DR, Coakley WT. Continuous cell washing and mixing driven by an ultrasound standing wave within a microfluidic channel. Lab Chip. 2004;4(5):446–52.CrossRefGoogle Scholar
Johansson L, Nikolajeff F, Johansson S, Thorslund S. On-chip fluorescence-activated cell sorting by an integrated miniaturized ultrasonic transducer. Anal Chem. 2009;81(13):5188–96.CrossRefGoogle Scholar
Yasuda K, Haupt SS, Umemura S, Yagi T, Nishida M, Shibata Y. Using acoustic radiation force as a concentration method for erythrocytes. J Acoust Soc Am. 1997;102(1):642–5.CrossRefGoogle Scholar
Haake A, Neild A, Kim DH, Ihm JE, Sun Y, Dual J, et al. Manipulation of cells using an ultrasonic pressure field. Ultrasound Med Biol. 2005;31(6):857–64.CrossRefGoogle Scholar
Petersson F, Nilsson A, Holm C, Jonsson H, Laurell T. Separation of lipids from blood utilizing ultrasonic standing waves in microfluidic channels. Analyst. 2004;129(10):938–43.CrossRefGoogle Scholar
Goddard G, Martin JC, Graves SW, Kaduchak G. Ultrasonic particle-concentration for sheathless focusing of particles for analysis in a flow cytometer. Cytometry A. 2006;69(2):66–74.CrossRefGoogle Scholar
Ai Y, Sanders CK, Marrone BL. Separation of Escherichia coli bacteria from peripheral blood mononuclear cells using standing surface acoustic waves. Anal Chem. 2013;85(19):9126–34.CrossRefGoogle Scholar
Lenshof A, Jamal A, Dykes J, Urbansky A, Åstrand-Grundström I, Laurell T, et al. Efficient purification of CD4+ lymphocytes from peripheral blood progenitor cell products using affinity bead acoustophoresis. Cytometry A. 2014;85(11):933–41.CrossRefGoogle Scholar
Evander M, Lenshof A, Laurell T, Nilsson J. Acoustophoresis in wet-etched glass chips. Anal Chem. 2008;80(13):5178–85.CrossRefGoogle Scholar
Austin Suthanthiraraj PP, Piyasena ME, Woods TA, Naivar MA, Lopez GP, Graves SW. One-dimensional acoustic standing waves in rectangular channels for flow cytometry. Methods. 2012;57(3):259–71.CrossRefGoogle Scholar
Shi J, Mao X, Ahmed D, Colletti A, Huang TJ. Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW). Lab Chip. 2008;8(2):221–3.CrossRefGoogle Scholar
Laurell T, Petersson F, Nilsson A. Chip integrated strategies for acoustic separation and manipulation of cells and particles. Chem Soc Rev. 2007;36(3):492–506.CrossRefGoogle Scholar
Yeo LY, Friend JR. Ultrafast microfluidics using surface acoustic waves. Biomicrofluidics. 2009;3(1):012002–23.CrossRefGoogle Scholar
Friend J, Yeo LY. Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics. Rev Mod Phys. 2011;83(2):647–704.CrossRefGoogle Scholar
Gedge M, Hill M. Acoustofluidics 17: theory and applications of surface acoustic wave devices for particle manipulation. Lab Chip. 2012;12(17):2998–3007.CrossRefGoogle Scholar
Lenshof A, Evander M, Laurell T, Nilsson J. Acoustofluidics 5: building microfluidic acoustic resonators. Lab Chip. 2012;12(4):684–95.CrossRefGoogle Scholar
Bora M, Shusteff M. Efficient coupling of acoustic modes in microfluidic channel devices. Lab Chip. 2015;15(15):3192–202.CrossRefGoogle Scholar
Piyasena ME, Austin Suthanthiraraj PP, Applegate RW, Goumas AM, Woods TA, Lopez GP, et al. Multinode acoustic focusing for parallel flow cytometry. Anal Chem. 2012;84(4):1831–9.CrossRefGoogle Scholar
Mueller A, Lever A, Nguyen T, Comolli J, Fiering J. Continuous acoustic separation in a thermoplastic microchannel. J Micromech Microeng. 2013;23(12):125006.CrossRefGoogle Scholar
Dow P, Kotz K, Gruszka S, Holder J, Fiering J. Acoustic separation in plastic microfluidics for rapid detection of bacteria in blood using engineered bacteriophage. Lab Chip. 2018; https://doi.org/10.1039/C7LC01180F.
Lin Y-S, Huang K-S, Hsieh W-C. An aluminum microfluidic chip fabrication using a convenient micromilling process for fluorescent poly(DL-lactide-co-glycolide) microparticle generation. Sensors. 2012;12:1455–67.CrossRefGoogle Scholar
Eghtesad A, Knezevic M. A new approach to fluid–structure interaction within graphics hardware accelerated smooth particle hydrodynamics considering heterogeneous particle size distribution. Comput Part Mech. 2017; https://doi.org/10.1007/s40571-017-0176-1.
Jahanmir S. Surface integrity in ultrahigh speed micromachining. Procedia Eng. 2011;19:156–61.CrossRefGoogle Scholar
Wiklund M, Gunther C, Lemor R, Jager M, Fuhr G, Hertz HM. Ultrasonic standing wave manipulation technology integrated into a dielectrophoretic chip. Lab Chip. 2006;6(12):1537–44.CrossRefGoogle Scholar
Nilsson A, Petersson F, Jonsson H, Laurell T. Acoustic control of suspended particles in micro fluidic chips. Lab Chip. 2004;4(2):131–5.CrossRefGoogle Scholar
Manneberg O, Melker Hagsäter S, Svennebring J, Hertz HM, Kutter JP, Bruus H, et al. Spatial confinement of ultrasonic force fields in microfluidic channels. Ultrasonics. 2009;49(1):112–9.CrossRefGoogle Scholar