Fig. 4.

Effects of ultrasound parameters on the MBs trapping efficiency. (A) The effect of duty cycle. Bright-field microscopy images (Upper) and corresponding sizes of trapped MBs (Lower) under different duty cycles (3–30%). The cluster size was not affected by increasing the duty cycle. The MBs concentration was 10.0 × 10⁸ MBs per milliliter and the acoustic pressure was 800 kPa. (B) The effect of acoustic pressure. Bright-field microscopy images (Upper) and corresponding sizes of trapped MB cluster (Lower) under different acoustic pressures (80–800 kPa). The cluster size decreased as the acoustic pressure increased. The MBs concentration and the duty cycle were 10.0 × 10⁸ MBs per milliliter and 30% m, respectively. (C) The effect of MB concentration. Bright-field microscopy images (Upper) and the sizes of corresponding trapped MBs (Lower) under different MBs concentrations (1.25–40.0 × 10⁸ MBs per milliliter). The cluster size increased with the MBs concentration. (D) The size distribution of MBs before and after AVT trapping. The acoustic pressure was 800 kPa, the duty cycle was 30%, and the MBs concentration was 10.0 × 10⁸ MBs per milliliter. (E) Stacked images showing dynamic control of trapped MBs to write “NTHU” (National Tsing Hua University) in the static condition. *P < 0.05.