Fig. 4: Long-range wireless DEP trapping experiment.
a The optimal trapping distance, x, for resonant wireless power transfer (WPT)—using the coplanar DEP electrodes in solution, was measured at 3 cm. For non-resonant WPT, the voltage is maximized at x = 0 cm. Using a nonlinear least squares fit of the coupling coefficient, the resonant and non-resonant wireless voltage gain across the coplanar electrodes could simultaneously be fit, see Supplementary Materials. b A simulation comparing the trapping radius for 200 nm PS particles using non-resonant and resonant WPT at a distance of x = 3 cm (3.5 VRMS, 1 MHz input signal). The resonant trapping radius (solid pink, 9.9 µm) is 7.6× longer than the non-resonant (black, 1.3 µm) trapping radius equating to a trapping volume that will be 58× bigger. Likewise, the trapping radius in which DEP can collect 200 nm PS particles 5× faster than diffusion at resonance (pink dashed line, 22.7 µm) is 17.5× longer than the non-resonant radius which equates to a trapping volume that is 305× larger. The radial distribution of the gradient of the E-field squared is plotted for reference. c Microscope images of the coplanar DEP device during wireless trapping of 1 µm, 200 nm, and 40 nm PS particles. The top left image is a bright-field image of the DEP coplanar device. The other top images depict wireless trapping and releasing of a 1 µm particle as the coil separation is increased beyond sufficient power coupling for trapping. The bottom three fluorescent images show the trap site loaded with their indicated particle size. See Supplementary Materials and Figure S4 for trap and release data of the 200 nm and 40 nm PS beads. d Experimental results comparing the maximal coil separation, x, in which trapping of 1 µm, 200 nm, and 40 nm PS particles could be maintained for non-resonant and resonant operation. The distance between the coils is nearly 3× farther when using resonant operation. Error bars indicate ±one standard deviation.
