Article pubs.acs.org/ac
Detachable Acoustofluidic System for Particle Separation via a Traveling Surface Acoustic Wave Zhichao Ma, David J. Collins, and Ye Ai* Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore 487372, Singapore S Supporting Information *
ABSTRACT: Components in biomedical analysis tools that have direct contact with biological samples, especially biohazardous materials, are ideally discarded after use to prevent cross-contamination. However, a conventional acoustofluidic device is typically a monolithic integration that permanently bonds acoustic transducers with microfluidic channels, increasing processing costs in single-use platforms. In this study, we demonstrate a detachable acoustofluidic system comprised of a disposable channel device and a reusable acoustic transducer for noncontact continuous particle separation via a traveling surface acoustic wave (TSAW). The channel device can be placed onto the SAW transducer with a high alignment tolerance to simplify operation, is made entirely of polydimethylsiloxane (PDMS), and does not require any additional coupling agent. A microstructured pillar is used to couple acoustic waves into the fluid channel for noncontact particle manipulation. We demonstrate the separation of 10 and 15 μm particles at high separation efficiency above 98% in a 49.5 MHz TSAW using the developed detachable acoustofluidic system. Its disposability and ease of assembly should enable broad use of noncontact, disposable particle manipulation techniques in practical biomedical applications related to sample preparation.
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biocompatible and label-free separation approach for various biomedical applications. Two types of acoustic wave, bulk acoustic wave (BAW) and surface acoustic wave (SAW), are typically used for particle manipulation in microfluidics. A BAW-based acoustofluidic device is fabricated by bonding a piezoelectric ceramic transducer (e.g., lead zirconate titanate) onto microfluidic channels made of high acoustic reflection materials such as silicon or glass, where an acoustic field develops in resonant channel structures.22−26 Conversely, a SAW is generated and propagates along the surface of a piezoelectric substrate and directly couples into a fluid or other materials only in the direct path of the acoustic beam.27,28 SAW transducers offer several advantages for microfluidic applications compared to BAW ones. SAW transducers are compatible with soft polymer materials that have been widely used to fabricate low cost microfluidic devices and are readily fabricated by depositing
eparation of microscopic particles, cells, and droplets is an essential technique for various biological research and medical applications. For example, separation and enrichment of low concentration microbes from complex biological samples is important for accurate and rapid medical diagnosis. The rapidly growing field of cell therapy also requires simple and efficient cell separation techniques that can speed up the collection of desired stem cells from complex samples.1 Microfluidics enables precise manipulation of biological cells, where manipulation methods include those based on dielectrophoresis,2,3 inertial focusing,4,5 magnetophoresis,6,7 optical tweezing,8,9 and acoustophoresis.10,11 Among these techniques, acoustophoresis has been successfully exploited to manipulate cells and particles thanks to its low power consumption and good biocompatibility.12−15 Though an oscillating sinusoidal field’s displacements time-average to zero, the difference in acoustic contrasts and energy densities between suspended particles and the fluid they are suspended in results in a time-averaged force.16,17 The correlation of the acoustic radiation force with size, density, and compressibility of the particles enables selective separation of particles according to their physical properties,18−21 which offers a © XXXX American Chemical Society
Received: February 14, 2016 Accepted: April 18, 2016
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DOI: 10.1021/acs.analchem.6b00605 Anal. Chem. XXXX, XXX, XXX−XXX
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Analytical Chemistry
PDMS is placed directly onto the SAW transducer with a high tolerance in alignment and orientation. This system can be assembled by hand and visually aligned without the aid of any special tools. After use, the PDMS channel device can be easily peeled off and discarded, while the SAW transducer can be recycled for future use. Using this system, we investigate the displacement of particles with varying sizes exposed to TSAWs at different frequencies. We also demonstrate the functionality of the developed detachable acoustofluidic system by separating differently sized polystyrene particles using TSAW, with a high separation efficiency of 98% in the case of 10 and 15 μm particles. This detachable acoustofluidic system provides a simple and cost-effective solution for particle and cell separation in practical biomedical applications.
interdigital transducers (IDTs) on a piezoelectric substrate. Their resonance frequency is determined by the dimensions of these electrodes, which can generate frequencies on the order of 10−1000 MHz,29 compared to the κc, we demonstrate the continuous separation of 10 and 15 μm particles in a 49.5 MHz TSAW, as shown in Figure 5a. The two types of particles were confined in the region near the channel wall closer to the TSAW source by a sheath flow, as shown in Figure 5b. The confined particles are then subject to a ∼ 6.3 mm wide TSAW field coupled into the fluid via the micropillar beneath the channel. As observed in Figure 3, the cutoff particle size in the 49.5 MHz TSAW is between 10 and 15 μm, such that 15 μm particles were effectively deflected to the opposite channel wall and flowed into outlet II, whereas the nondisplaced 10 μm particles followed the fluid streamlines and exited via outlet I, as shown in Figure 5c. The video of the particle separation process is available in Video S3 in the Supporting Information. Separation experiments with the same flow condition at varying input voltages were conducted to evaluate the effect of
Figure 6. Effect of input voltage on separation performance. This figure shows the percentage of 15 μm particles deflected to the outlet II (separation efficiency), the percentage of all particle exiting via outlet I that are 10 μm particles (purity I) and the percentage of all particle exiting via outlet II that are 15 μm particles (purity II). While increasing TSAW strength results in increased 15 μm particle deflection, no such relationship is observed for 10 μm particles at any input voltage.
outlet junction were tracked using a high-speed camera. Here, separation efficiency is defined as the percentage of all 15 μm particles deflected to the outlet II. When the input voltage was lower than 15.4 Vpp, no 15 μm particles could be effectively deflected into outlet II. Above this value, separation efficiency increases markedly for higher voltages, where a plateaued high efficiency above 98% is achieved for applied voltages greater than 22.0 Vpp. The purity I and II values in Figure 6 are defined as the percentage of 10 and 15 μm particles out of the F
DOI: 10.1021/acs.analchem.6b00605 Anal. Chem. XXXX, XXX, XXX−XXX
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Analytical Chemistry
(2) Song, Y.; Sonnenberg, A.; Heaney, Y.; Heller, M. J. Electrophoresis 2015, 36, 1107−1114. (3) Kang, Y.; Li, D.; Kalams, S. A.; Eid, J. E. Biomed. Microdevices 2008, 10, 243−249. (4) Hou, H. W.; Warkiani, M. E.; Khoo, B. L.; Li, Z. R.; Soo, R. A.; Tan, D. S.-W.; Lim, W.-T.; Han, J.; Bhagat, A. A. S.; Lim, C. T. Sci. Rep. 2013, 3, 1259. (5) Warkiani, M. E.; Guan, G.; Luan, K. B.; Lee, W. C.; Bhagat, A. A. S.; Chaudhuri, P. K.; Tan, D. S.-W.; Lim, W. T.; Lee, S. C.; Chen, P. C. Lab Chip 2014, 14, 128−137. (6) Han, K.-H.; Frazier, A. B. J. Appl. Phys. 2004, 96, 5797−5802. (7) Lim, J. K.; Chieh, D. C. J.; Jalak, S. A.; Toh, P. Y.; Yasin, N. H. M.; Ng, B. W.; Ahmad, A. L. Small 2012, 8, 1683−1692. (8) Jung, J. H.; Lee, K. H.; Lee, K. S.; Ha, B. H.; Oh, Y. S.; Sung, H. J. Microfluid. Nanofluid. 2014, 16, 635−644. (9) Li, Y.; Xin, H.; Cheng, C.; Zhang, Y.; Li, B. Nanophotonics 2015, 4, 353−360. (10) Li, P.; Mao, Z.; Peng, Z.; Zhou, L.; Chen, Y.; Huang, P.-H.; Truica, C. I.; Drabick, J. J.; El-Deiry, W. S.; Dao, M. Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 4970−4975. (11) Collins, D. J.; Neild, A.; deMello, A.; Liu, A.-Q.; Ai, Y. Lab Chip 2015, 15, 3439−3459. (12) Wiklund, M. Lab Chip 2012, 12, 2018−2028. (13) Collins, D. J.; Morahan, B.; Garcia-Bustos, J.; Doerig, C.; Plebanski, M.; Neild, A. Nat. Commun. 2015, 6, 8686. (14) Destgeer, G.; Ha, B. H.; Park, J.; Sung, H. J. Anal. Chem. 2016, 88, 3976. (15) Destgeer, G.; Cho, H.; Ha, B. H.; Jung, J. H.; Park, J.; Sung, H. J. Lab Chip 2016, 16, 660−667. (16) Yosioka, K.; Kawasima, Y. Acta Acustica united with Acustica 1955, 5, 167−173. (17) Chu, B. T.; Apfel, R. E. J. Acoust. Soc. Am. 1982, 72, 1673−1687. (18) Jo, M. C.; Guldiken, R. Sens. Actuators, A 2012, 187, 22−28. (19) Shi, J.; Huang, H.; Stratton, Z.; Huang, Y.; Huang, T. J. Lab Chip 2009, 9, 3354−3359. (20) Petersson, F.; Nilsson, A.; Holm, C.; Jönsson, H.; Laurell, T. Lab Chip 2005, 5, 20−22. (21) Nam, J.; Lim, H.; Kim, C.; Kang, J. Y.; Shin, S. Biomicrofluidics 2012, 6, 024120. (22) Petersson, F.; Åberg, L.; Swärd-Nilsson, A.-M.; Laurell, T. Anal. Chem. 2007, 79, 5117−5123. (23) Laurell, T.; Petersson, F.; Nilsson, A. Chem. Soc. Rev. 2007, 36, 492−506. (24) Hahn, P.; Leibacher, I.; Baasch, T.; Dual, J. Lab Chip 2015, 15, 4302−4313. (25) Leibacher, I.; Reichert, P.; Dual, J. Lab Chip 2015, 15, 2896− 2905. (26) Mishra, P.; Hill, M.; Glynne-Jones, P. Biomicrofluidics 2014, 8, 034109. (27) Rezk, A. R.; Manor, O.; Friend, J. R.; Yeo, L. Y. Nat. Commun. 2012, 3, 1167. (28) Sesen, M.; Alan, T.; Neild, A. Lab Chip 2014, 14, 3325. (29) Shilton, R. J.; Travagliati, M.; Beltram, F.; Cecchini, M. Adv. Mater. 2014, 26, 4941−4946. (30) Skowronek, V.; Rambach, R. W.; Franke, T. Microfluid. Nanofluid. 2015, 19, 335−341. (31) Skowronek, V.; Rambach, R. W.; Schmid, L.; Haase, K.; Franke, T. Anal. Chem. 2013, 85, 9955−9959. (32) Collins, D. J.; Neild, A.; Ai, Y. Lab Chip 2016, 16, 471−479. (33) Destgeer, G.; Lee, K. H.; Jung, J. H.; Alazzam, A.; Sung, H. J. Lab Chip 2013, 13, 4210−4216. (34) Destgeer, G.; Ha, B. H.; Jung, J. H.; Sung, H. J. Lab Chip 2014, 14, 4665−4672. (35) Ma, Z.; Guo, J.; Liu, Y. J.; Ai, Y. Nanoscale 2015, 7, 14047− 14054. (36) Collins, D. J.; Morahan, B.; Garcia-Bustos, J.; Doerig, C.; Plebanski, M.; Neild, A. Nat. Commun. 2015, 6, 8686. (37) Shi, J.; Ahmed, D.; Mao, X.; Lin, S.-C. S.; Lawit, A.; Huang, T. J. Lab Chip 2009, 9, 2890−2895.
total number of particles collected in outlets I and II, respectively. Once the input voltage was above 15.4 Vpp, 15 μm particles were deflected from a trajectory that would result in their exiting via outlet I. Thus, Purity I also increases with the input voltage and reaches 99% above 22.0 Vpp. Purity II remains above 99% once the input voltage was above 15.4 Vpp, owing to the minimal response of 10 μm particles in a κ < κc condition.
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CONCLUSION We demonstrated for the first time a detachable acoustofluidic system consisting of a disposable channel device and a reusable SAW transducer for continuous size-based particle separation. This channel is entirely composed of PDMS, and can efficiently couple substrate displacements into the fluid channel without the need for a separate step to bond the channel to the substrate. This permits the reversible attachment and postuse disposal of the contaminated channel while retaining the SAW actuator for reuse. Important for clinical use, the placement of the channel device on the SAW transducer can be implemented by hand, without the aid of any special alignment tools. The high tolerance in alignment is demonstrated by equivalent particle deflections with up to a 25° angle between the channel and the SAW transducer. This work has further demonstrated that effective particle manipulation only occurs for particles above a cutoff size, where acoustic forces are only sufficient for rapid particle translation as the particle diameter approaches the fluid wavelength. Utilizing this effect, we have demonstrated the separation of 10 and 15 μm particles in a 49.5 MHz TSAW at 98% efficiency. Because the inexpensive channel component can be discarded after use while the microfabricated SAW device can be reused, the presented acoustofluidic system is an important development for practical, cost-effective biomedical applications.
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ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.analchem.6b00605. Deflection of 5, 7, 10, and 15 μm particles in 24.7/49.5/ 99.0 MHz TSAW field (AVI) Deflection of 10 and 15 μm particles in the parallel positioned and rotated microchannels (AVI) Separation of 10 and 15 μm particles in the detachable acoustofluidic system (AVI)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Phone: (+65) 6499 4553. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We gratefully acknowledge the support received from SUTDMIT International Design Center (Grant IDG11300101) awarded to Y.A.
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REFERENCES
(1) Schriebl, K.; Lim, S.; Choo, A.; Tscheliessnig, A.; Jungbauer, A. Biotechnol. J. 2010, 5, 50−61. G
DOI: 10.1021/acs.analchem.6b00605 Anal. Chem. XXXX, XXX, XXX−XXX
Article
Analytical Chemistry (38) Chen, Y.; Li, S.; Gu, Y.; Li, P.; Ding, X.; Wang, L.; McCoy, J. P.; Levine, S. J.; Huang, T. J. Lab Chip 2014, 14, 924−930. (39) Skotis, G.; Cumming, D.; Roberts, J.; Riehle, M.; Bernassau, A. Lab Chip 2015, 15, 802−810. (40) Ding, X.; Peng, Z.; Lin, S.-C. S.; Geri, M.; Li, S.; Li, P.; Chen, Y.; Dao, M.; Suresh, S.; Huang, T. J. Proc. Natl. Acad. Sci. U. S. A. 2014, 111, 12992−12997. (41) Destgeer, G.; Sung, H. J. Lab Chip 2015, 15, 2722−2738. (42) Ai, Y.; Sanders, C. K.; Marrone, B. L. Anal. Chem. 2013, 85, 9126−9134. (43) Collins, D. J.; Alan, T.; Neild, A. Lab Chip 2014, 14, 1595− 1603. (44) Collins, D. J.; Alan, T.; Helmerson, K.; Neild, A. Lab Chip 2013, 13, 3225−3231. (45) Travagliati, M.; Shilton, R. J.; Pagliazzi, M.; Tonazzini, I.; Beltram, F.; Cecchini, M. Anal. Chem. 2014, 86, 10633−10638. (46) Hodgson, R. P.; Tan, M.; Yeo, L.; Friend, J. Appl. Phys. Lett. 2009, 94, 024102. (47) Cooper, J. J. Acoust. Soc. Am. 2012, 131, 3303−3303. (48) Reboud, J.; Wilson, R.; Zhang, Y.; Ismail, M. H.; Bourquin, Y.; Cooper, J. M. Lab Chip 2012, 12, 1268−1273. (49) Kishor, R.; Seah, Y.; Zheng, Y.; Xia, H.; Wang, Z.; Lu, H.; Lim, T. Sens. Actuators, A 2015, 233, 360−367. (50) O’Rorke, R.; Wood, C.; Wälti, C.; Evans, S.; Davies, A.; Cunningham, J. J. Appl. Phys. 2012, 111, 094911. (51) Witte, C.; Reboud, J.; Wilson, R.; Cooper, J.; Neale, S. Lab Chip 2014, 14, 4277−4283. (52) Guo, F.; Xie, Y.; Li, S.; Lata, J.; Ren, L.; Mao, Z.; Ren, B.; Wu, M.; Ozcelik, A.; Huang, T. J. Lab Chip 2015, 15, 4517−4523. (53) Rambach, R. W.; Skowronek, V.; Franke, T. RSC Adv. 2014, 4, 60534−60542. (54) Collins, D. J.; Alan, T.; Neild, A. Appl. Phys. Lett. 2014, 105, 033509. (55) Tan, M. K.; Friend, J. R.; Matar, O. K.; Yeo, L. Y. Phys. Fluids 2010, 22, 112112. (56) Ai, Y.; Marrone, B. L. Microfluid. Nanofluid. 2012, 13, 715−722. (57) Guo, J.; Kang, Y.; Ai, Y. J. Colloid Interface Sci. 2015, 455, 203− 211. (58) Destgeer, G.; Ha, B. H.; Park, J.; Jung, J. H.; Alazzam, A.; Sung, H. J. Anal. Chem. 2015, 87, 4627−4632. (59) Dentry, M. B.; Yeo, L. Y.; Friend, J. R. Phys. Rev. E 2014, 89, 013203. (60) Destgeer, G.; Im, S.; Ha, B. H.; Jung, J. H.; Ansari, M. A.; Sung, H. J. Appl. Phys. Lett. 2014, 104, 023506.
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DOI: 10.1021/acs.analchem.6b00605 Anal. Chem. XXXX, XXX, XXX−XXX
