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Sriphutkiat Y, et al

Figure 2. Numerical simulation of (A) 10 μm-cell trajectory excited by low- (10.4 MHz) and (B) high- (23.8 MHz) frequency
standing surface acoustic wave across the cavity at the power of 0.5 W from different initial positions to the pressure nodes, and (C)
the effect of thediameter of cell (8 μm, 10 μm, and 15 μm) at the excitation power of 1.0 W and (D) the effect of excitation power
(0.1 W, 0.5 W, and 1.0 W) on motion of 10-μm diameter cellat thelow and high frequency with the same initial distance to the
corresponding pressure node of 42 μm.

Table 2. Correlation between acoustic parameters and cell motion of microparticles have already been found to enhance the
by SSAW motion velocity of microparticles [42,48] . In comparison to
Distance Cell motion Time to reach Size of cell the solid microparticles in the similar size, cells usually
Parameters between velocity pressure node spheroid
pressure nodes have lower compressibility and density so that their motion
[49,50]
Excitation Decrease Increase Decrease Decrease speed is slower . In order to reduce the time of reaching
frequency the pressure node higher output power is required, which
Power output Constant Increase Decrease Constant leads to high temperature elevation of the substrate during
Cell diameter Constant Increase Decrease Increase the IDTs excitation. Another potential side effect of acoustic
manipulation of cells is due to the mechanical impact.
At the high frequency, cells in the diameter of 10 m reach However, previous studies show that acoustic excitation at
the pressure node at 37.79 s, 8.00 s, and 4.01 s at the output the power of about 0.87 W does not decrease the cell viability
power of 0.1W, 0.5W, and 1.0W, respectively. In comparison, significantly, but occasionally could even enhance the cell
the corresponding values at the low-frequency excitation activities [38,51] . Moreover, the initial location is one of the
are 89.27s, 17.37s, and 8.70s, respectively. The enhancement important factors for the cell accumulation time. The
of high-frequency excitation for cells in different sizes at distribution of an acoustic radiation force from the standing
varied output power is similar, ~2.2 fold, which is slightly waves is not uniform across the microchannel width [52] ,
lower than the ratio of excitation frequency (2.4 fold). pointing from the anti-pressure node toward the pressure
The trajectory motion of microparticles, either solid node. Both pressure nodes and anti-pressure node locations
microspheres or cells, by the SSAW is able to be calculated have the lowest magnitude of acoustic radiation force in
and validated [46,47] . The high output power and large size the standing wave field. Thus, cells located nearby the anti-

International Journal of Bioprinting (2018)–Volume 4, Issue 1 5