Supplementary Materials

Turning a surface superrepellent even to completely wetting liquids

Tingyi “Leo” Liu, Chang-Jin “CJ” Kim

Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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  • Materials and Methods
  • Supplementary Text
  • Figs. S1 to S9
  • Tables S1 and S2
  • Captions for Movies S1 to S7
  • Full Reference List

Images, Video, and Other Other Media

Movie S1
Comparison of liquid repellency on a smooth Teflon® surface and a superomniphobic silica surface. Three liquids of water, methanol and FC-72, are used to illustrate the wetting properties of the structured silicon dioxide vs. smooth Teflon®. Teflon® repels water (i.e., hydrophobic) but is wetted moderately by methanol (i.e., oleophilic) and completely by FC-72. In contrast, our structured silicon dioxide surface super-repels all three liquids similarly. The video was replayed at 2x. (QuickTime, 1.6 MB)
Movie S2
Water, methanol, and FC-72 beading and rolling on a superomniphobic silica surface. All three liquids of water, methanol and FC-72 dispensed on our structured silicon dioxide surface (i.e., the central dull-grey square on the sample) bead and roll around, demonstrating superomniphobicity of the surface. However, the droplets spread spontaneously on smooth silicon dioxide (i.e., the outer frames of grey and blue/purple), as shown at the end of the video clip. Note all three liquids behave similarly despite their large differences in surface tension. (QuickTime, 2.3 MB)
Movie S3
Contact lines of FC-72 advancing and receding on a surface with doubly re-entrant silica posts. The droplet was expanded or contracted by pumping the liquid in and out of the syringe (with BD PrecisionGlide Needle, 22 G x 1 1/2 inch). Video was replayed at normal speed. (QuickTime, 573 KB)
Movie S4
A droplet of FC-72 evaporating on a surface with doubly re-entrant silica posts. The droplet collapsed while receding between resting on 5 posts and 4 posts, transitioning to complete wetting (i.e. Wenzel state) with ~0° advancing contact angle. The liquid continued to evaporate and eventually dried, also showing a ~0° receding contact angle. Video was replayed at normal speed. (QuickTime, 535 KB)
Movie S5
Water, methanol, and FC-72 droplets bouncing on surfaces with doubly re-entrant silica posts. Droplets of water, methanol and FC-72 were released from a syringe and collided on the surface with doubly re-entrant structured posts with Weber number We ~ 0.70, 0.55, 0.42, respectively. Each droplet deformed and bounced off the surface and underwent a vibration before settling down on the surface. For water and methanol, a surface with 100 μm spaced posts was used, while for FC-72 a surface with 50 μm spaced posts was needed to realize the bouncing. Videos were filmed at 6000 fps and replayed 20 times slower at 30 fps. (QuickTime, 740 KB)
Movie S6
Super-repellency of the surface with doubly re-entrant silica posts confirmed at high temperatures. Droplets of FC-70 and ionic liquid [EMIM][BF4] dispensed from a pipette on the heated surface stayed beaded and continued rolling around, demonstrating the reported surface stays super-repelling at high temperatures. At the end of each video clip, the droplet touches the smooth silicon dioxide (i.e., the outer areas of the sample surface appearing grey and green) and spreads spontaneously. The temperature of the hotplate is indicated by the surface thermometer placed alongside the test surface. (QuickTime, 6.4 MB)
Movie S7
Compatibility of the superomniphobic silica surface with biological fluids demonstrated using a droplet of sheep serum. The superomniphobic SiO2 surface stays super-repellent to the serum even after a prolonged contact (> 2 hours), while the Teflon®-coated superhydrophobic surface loses its repellency in ~0.5 hour. A serum droplet continues to slide back and forth on each surface during the test. The first 2 cycles of sliding are played at normal speed and show no pinning on both surfaces. The video is then played at 100x speed. On the superhydrophobic Teflon® surface, the droplet starts to show a sign of pinning at ~30 minutes, and its right edge is completely pinned at ~36 minutes. The video slows down to the normal speed for 2 cycles to clearly present the stretching of the droplet by the pinning before returning to the 100x speed till the end. As the droplet shrinks, the pinning makes it detached from the needle at ~1 hour. In contrast, there is no sign of pinning on the superomniphobic SiO2 surface until ~2.3 hours, when the droplet accidentally encounters a surface defect. (QuickTime, 6.3 MB)