# Versatile High-Throughput Platform for Focused Ultrasound In Vitro Application
## 3 Results
### Influence of Filling Volume
#### 3.3.2 HIFU Platform  
The same measurements were conducted to examine the influence of the filling volumes on the sound pressure in the individual wells, this time for the HIFU platform (1 MHz). The scan settings were identical to the LIFU case (Filling 200-350 \(\mu\)L, z-scan from 1 mm to 10 mm in 0.1 mm steps). Figure 14 illustrates the results of these measurements.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & **200 \(\mu\)L** & **250 \(\mu\)L** & **300 \(\mu\)L** & **350 \(\mu\)L** \\ \hline mean p\({}_{\rm max}\) [kPa] & 244.78 & 286.35 & 286.65 & 294.20 \\ SD p\({}_{\rm max}\) [kPa] & 106.70 & 112.96 & 108.78 & 107.15 \\ mean z\({}_{\rm pos}\) [mm] & 6.05 & 7.38 & 8.59 & 9.04 \\ SD z\({}_{\rm pos}\) [mm] & 0.66 & 0.63 & 0.75 & 1.46 \\ \hline \end{tabular}  
\({}^{\rm p_{max}}\) = maximum pressure, z\({}_{\rm pos}\) = z-position of maximum pressure, SD = standard deviation.  
\end{table}
Table 2: Maximum sound pressure levels in the 48 wells at different filling volumes and positions within the wells.  
Figure 14: Results of hydrophone measurements with the 1 MHz HIFU platform along the z-axis in a representative well of a 96-well plate. Measurements were taken from the bottom of the well (z = 1 mm) to the maximum filling level for the different filling volumes (200 \(\mu\)L, 300 \(\mu\)L, 350 \(\mu\)L). Additional free-field measurements were performed at identical positions (no well). The step size along the z-axis was 0.1 mm.  
Figure 13: Results of hydrophone measurements with the 1.5 MHz LIFU platform. The ratio of filling volume and measuring position in the well along the z-axis in the 48 wells from the bottom of the well (z = 1 mm) to the maximum filling level at the different filling volumes (200 \(\mu\)L, 250 \(\mu\)L, 300 \(\mu\)L, 350 \(\mu\)L) was analyzed. The step size along the z-axis was 0.1 mm. The influence of the filling volume on the maximum pressure and position of maximum pressure from measurements was analysed in 48 single wells. (**a**) Data are presented as a scatter plot. (**b**) Data are presented as a bar diagram, including mean value and SD.  
The results of this investigation, as illustrated in Figure 15, demonstrated the impact of varying filling volumes on sound pressure levels across 32 distinct wells. The results of the maximum sound pressure (p\({}_{\text{max}}\)) when driven with a voltage of V\({}_{\text{peak}}\) 20 V for the individual filling volumes are presented in Table 3. The observed variation ranged from 197 kPa (SD 40 kPa) for 200 \(\mu\)L to 255 kPa (SD 47 kPa) for 350 \(\mu\)L filling. The results of the HIFU platform indicated that the influence of different filling volumes in the well was minimal. The axial positions at which the maximum sound pressures were measured were approximately the same for all filling volumes, varying only between 2.36 (200 \(\mu\)L) and 2.14 mm (350 \(\mu\)L). Furthermore, these values differed only marginally from the measurements taken without the well plate.  
The results of these investigations demonstrated that the sound pressure distribution within the well was almost independent of the water filling volume, in contrast to the LIFU platform, which was only capable of natural focusing.