2.7 Image Acquisition and Analysis
We captured the images of the electrode array using the Nikon Eclipse upright optical microscope with 10X objective during the experiments, as illustrated in Figure 2 . The image acquisition rate was 5 frames/second. We used ImageJ software to convert the image sequences into the videos of the experiments, Supplementary Video 1 . We manually determined the positions of the cells in the electrode array for a given frequency using ImageJ. We determined the crossover frequency and pDEP behavior of the cells in the electrode array.
We categorized the DEP behavior of the cells according to positions of the cells in the electrode array when electric field was applied. We scored the strength of the DEP force “+3” when the cells were in contact with the edges of the electrodes (Figure 2 : Green triangle, 3). The DEP force was “0” when the cells were experiencing the lowest DEP force in the middle of the channel (SiO2/Si, Figure 2 : Cyan triangle, 0). Afterwards, the magnitude of the DEP forces was determined either “+2” (Figure 2 : White triangle, 2) or “+1” (Figure 2 : Pink triangle, 1) according to their location in between two electrodes.
Since we did not observe clear nDEP responses of U87 glioma cells under these DEP conditions. We measured the mean values of the positions of the cells relative to the edges of the electrodes using ImageJ. We plotted the mean positions of the cells with standard deviations as a function of frequency using Prism 9 software (GraphPad).