Published: August 21st, 2018
A protocol for manipulating the microparticles in a microfluidic channel with a dual-frequency excitation is presented.
We demonstrate a method for increasing the tuning ability of a standing surface acoustic wave (SSAW) for microparticles manipulation in a lab-on-a-chip (LOC) system. The simultaneous excitation of the fundamental frequency and its third harmonic, which is termed as dual-frequency excitation, to a pair of interdigital transducers (IDTs) could generate a new type of standing acoustic waves in a microfluidic channel. Varying the power and the phase in the dual-frequency excitation signals results in a reconfigurable field of the acoustic radiation force applied to the microparticles across the microchannel (e.g., the number and location of the pressure nodes and the microparticle concentrations at the corresponding pressure nodes). This article demonstrates that the motion time of the microparticle to only one pressure node can be reduced ~2-fold at the power ratio of the fundamental frequency greater than ~90%. In contrast, there are three pressure nodes in the microchannel if less than this threshold. Furthermore, adjusting the initial phase between the fundamental frequency and the third harmonic results in different motion rates of the three SSAW pressure nodes, as well as in the percentage of microparticles at each pressure node in the microchannel. There is a good agreement between the experimental observation and the numerical predictions. This novel excitation method can easily and non-invasively integrate into the LOC system, with a wide tenability and only a few changes to the experimental set-up.
LOC technology integrates one or several functions on a microchip for biology, chemistry, biophysics, and biomedical processes. LOC allows a laboratory set-up on a scale smaller than sub-millimeters, fast reaction rates, a short response time, a high process control, a low volume consumption (less waste, lower reagents cost, and less required sample volume), a high throughput due to parallelization, a low cost in the future mass production and cost-effective disposables, a high safety for chemical, radioactive, or biological studies, and the advantages of a compact and portable device1,2. Precise cell manipula....
1. Preparation of the Microfluidic Channel
2. Fabrication of the Interdigital Transducers
The distributions of the acoustic pressure and the acoustic radiation force of an SSAW at the dual-frequency excitation (6.2 and 18.6 MHz) are shown in Figure 1. Here, the dual-frequency excitation occurs on polystyrene microparticles (4 µm in diameter) in a microchannel with a width of 300 µm at an acoustic power of 146 mW. The resultant acoustic pressure is always in phase when P1 > 90% so that only one pressure node is pre.......
The microparticle motion in the microchannel by an SSAW at the dual-frequency excitation was extensively investigated in this study, and an effectively tunable patterning technique by varying the dual-frequency excitation signals was developed and tested. The production of such a waveform is easily realized by most function generators, and the adjusting approach is very convenient. Both the S12- and S11-frequency responses of the fabricated IDTs illustrate several resonant modes34<.......
|poly-dimethylsiloxane elastomer base
|negative tone photoresist
|double-side polished LiNbO3 wafer
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