Fig. 4: Demonstration for EPD’s compatibility with bio-samples and substrates.

A Schematic diagram of EPD’s compatibility with bio-samples, including body fluids, protein, and living cells. B Optical images showing the EPD-based actuation of body fluids, including human serum, saliva, and urine. Scale bars: 3 mm. C Series of fluorescence microscope images showing the EPD-based actuation of fluorescent protein solution. The fluorescence intensity (in arbitrary units, arb. units) on the trajectory of the droplet or inside the droplet before and after droplet movement shows no significant difference (paired t-test, P > 0.05), demonstrating that no protein residue can be observed in the EPD-based droplet actuation. Error bars, SD (n = 4). D EPD-based actuation of living A549 cells within culture medium, where the percentage of living cells is analyzed and compared with the control group in air. Error bars, SD (n = 3). E Variation of viable and nonviable cell concentrations after being treated by EPD/EWOD for 30 min and then incubated for another 12 h, demonstrating the effect on cell proliferation capacity by EPD and EWOD. Error bars, SD (n = 3). F Schematic diagram of EPD’s compatibility with various surroundings and substrates. G Optical images showing the EPD-based droplet actuation in air, on the hydrophobic surface. Scale bars: 3 mm. H Optical images showing the EPD-based actuation of droplet floating at oil-air interface, with an oil substrate which has a higher density \(\rho\) than water. Scale bars: 3 mm. I Optical images showing the EPD-based actuation of droplet merged in oil surrounding which has a lower density \(\rho\) than water, with a hydrophobic substrate. Scale bars: 3 mm. Source data are provided as a Source Data file.