Fig. 6 (a) The insulating electrode sheet. (b) The electric field applied partial device. (c) High frequency electric field generator experimental setup.

Cell Viability

The high frequency AC field with 200 kHz was applied to U251 cells for 24 h, and 48 h respectively. An oscilloscope (Teledyne Lecroy, WS3034), a Teledyne LeCroy PP020 passive probe and a Pearson Current probe (Model 6600, Pearson Electronics, Inc., Palo Alto, CA, USA) were used to measure the voltage and current during the experiments. After the stimulation, 1 mL of 1640 medium was added to inactivate trypsin-EDTA and centrifuged at 800 rpm for 5 minutes. Then the supernatant was discarded, and 1mL new 1640 medium was added in the cell suspension. Subsequently, the cell suspension was transferred into 96-well plates (100 μL/well). 20 μL of CCK-8 (Dojindo, Japan) was added to each well of the 96-well plate, and the incubation was continued for 1 hour at 37 ℃. Finally, the absorbance of cells was analyzed by a microplate reader (H1-Synergy, USA). Cell viability was calculated from the absorbance of cells both in the treated and control groups. The experiments were performed three times at least.

Establishment and Feasibility Analysis of Finite Element Simulation

Before the cell experiment, a proportional simulation model was built using COMSOL Multiphysics to verify the feasibility of the experimental scheme. The relative dielectric constants and conductivity parameters used in the simulation model are shown in Table 3.
Table 3 Simulation Parameters of the Devices in the Cell Plate