Fig. 5: Application examples of ion-beam-induced-film-wetting.

a, b Proof-of-concept gas sensing prototype. a Optical image of IBFW film that connects two droplets settled on Au electrodes. b Results of IBFW nano-circuit humidity sensor compared with a micrometer droplet circuit. The inset shows the schematic of the IBFW humidity sensor. The dash lines are the linear fitting results of drainage-source currents of microdroplet and nanofilm. The voltage exerted is 1 V. c In-situ chemical reaction chip. The left is the schematics, crosshair channels connect four droplets which are used to inject reagent water solutions. 0.1 μL of 0.1 M NaSCN, 0.1 mM Co²⁺, 0.1 mM Fe³⁺ and 0.1 mM Cu²⁺ are injected clockwise into four droplets. The inset on the bottom-left shows the microchip on fingertip, with red circle shows the four droplets, the edge of the SiO₂ substrate is 10 mm. The right part is the optical image of the reaction chip that has been stored in vacuum chamber for 48 h after the injection, the purple boxes are 80 μm × 80 μm. d Schematics of a three-electrode electrochemistry experiment. Analytes are dissolved in the droplet with IBFW film pattern printed onto the working electrode. 10 nm Au and 5 nm Ti serve as the working electrode, Pt probe and silver-plated probe stuck into the droplet are the counter and pseudo-reference electrodes respectively. e Optical images of the patterned solid particles deposited on Au electrode surface. The upper part shows Ag particles (20 μm × 3 μm rectangle with PKU letters) deposited at −0.2 V. The lower part shows blue AgTCNQ particles (50 μm × 10 μm) deposited at −0.1 V. Both are potentiostatically deposited for 180 s. Cyclic-voltammograms of (f) 10 mM Ag⁺([EMIM][NTf₂]) and (g) 6 mM Ag⁺ and 5 mM TCNQ ([EMIM][NTf₂]) solution. f The reduction peak appears at −0.295 V, with peak current decreases with cycles. g The first reduction peak (Ag⁺ to Ag) appears at 0.095 V. The +300 mV shift at present of TCNQ is consistent with literature⁴⁴. All optical images are acquired by Leica DM4B microscope.