Fig. 3: Theoretical analysis, experimental and simulation results of ion-beam-induced-film-wetting mechanism.

a Experimental helium focused ion beam dosage density to induce ionic liquid flow (ions/nm²) and calculated results of critical dose density to induce significant ion emission. The inset shows when the scan position is separated too far from the contact line, the consecutive liquid film degenerates to the local protrusion flow as shown in Fig. 1b. The scale bar is 5 μm. b IBFW induced liquid film lengths (μm) on substrates with different conductivities. Experimental film length data of distinct samples are presented as mean ± s.d. n = 5. The right ordinate represents the overall ion emission number calculated by the beam parameters and sample characters. In the horizontal axis, TOX stands for thermal oxidized, and CVD stands for chemical vapor deposited. c Molecular dynamics simulation of [EMIM][DCA] droplet (640 ion pairs) deposited on fused silica substrate going through surface charges injection and removal. The arrows indicate the most directed movements of ions: the pale blue arrows at the beginning stage represent the surface charge induced primary anion emission; the purple arrows of cations represent the emitted anions induced secondary cation emission. d IBFW film flow speed as a function of liquid film length. The single spot experiments are conducted with a line pattern of scan spots, at constant beam current 1 pA, dwell time 10 μs, spacing 1 nm. The change width experiments are conducted with rectangular pattern with constant length 20 μm and different widths, while keeping the beam current 1 pA, dwell time 2 μs, spacing 1 nm. Data of change width method are presented as mean ± s.d. n = 12. The blue shaded region is the calculated velocity range due to the range of slip lengths^58,59, the deep blue line is the calculated result employing the average slip length⁵⁸.