The effect of phase modulation in dual-frequency excited standing surface acoustic wave (SSAW) on microparticle manipulation

Standing surface acoustic wave (SSAW) in a microfluidic channel generated from a pair of interdigital transducers (IDTs) has already shown its capability of particle accumulation at the pressure node and its potential in biomedical research. Manipulation of cells or microparticles to the desired position precisely is an important issue of this technology. Using the phase modulation in the dual-frequency excitation, the fundamental and third harmonic of the same IDTs simultaneously with the initial phase difference between them and the power ratio of the fundamental wave to the third harmonic of 85%, the positions of three pressure nodes of the SSAW in the microchannel moves at different rates because of changes to the syn-thesized waveform and resultant acoustic radiation force. Meanwhile, percentages of microparticles at each pressure node also vary with the initial phase. Experimental measurement of green fluorescent microspheres in a diameter of 4 mu m in a 300 mu m-microchannel driven by SSAW at 6.2 and 17.7 MHz simultaneously has a good correlation with the numerical prediction (R-2 = 0.967 and 0.89 for the position of each pressure node and the percentage of microspheres accumulated at each pressure node in the range of initial phase from 0 degrees to 360 degrees, respectively, where R is the correlation coefficient). This proposed method could provide more tunability for SSAW-based microparticle manipulation with few changes to the setup of labon-a-chip system. (C) 2021 Elsevier B.V. All rights reserved.