The researchers found that micro-patterning can result in a highly transparent ultra-oil coating

Keywords: Ultra-hydrophobic Ultra-sparse Oil Wear-resistant Transparent PDMS
Background:
Based on ultra-cleaned oil high-transparency coatings with self-cleaning, anti-fouling, low resistance and anti-fouling properties, it has received widespread attention in industrial applications such as optical devices, solar panels and self-cleaning windows, but the lack of mechanical durability has been unresolved in many ultra-oil coatings produced to date.
polymethylsilioxane (PDMS) is a general-purpose material with good biosycontability, chemical stability, transparency and mechanical elasticity. It is widely used in biomedical equipment, including microflower and nanoflower equipment

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Bionamics and Bionic Nano Probe Laboratory (NLBB) and Samuel Martin of The Ohio State University, between micromodulated and hydrophobic SiO2 nanoparticles and methyl benzene resin adhesive coatingS super-hydrophobic, followed by gas-phase deposition of fluosilane on the coating to make it ultra-oily (Figure 1). The findings were published last year in Journal of Colloid and Interface Science.
Figure 1 Fluorinated Nanoparticles/Adhesive Coatings
Research:
1, PDMS substrate and coating treatment
cleans the PDMS substrate with an ultrasonic bath (45kHz frequency) in isopropyl alcohol for 15min. Then, rinse the substrate with deionized water and dry it.
600mg hydrophobic silica nanoparticles (10nm diameter) were dispersed over a 30mL volume ratio of 40% tyfuran and 60% IPA. The mixture was ultrasonicly treated with an ultrasonic ionizer (20kHz frequency, 35% amplitude). Then, add 150 mg of methyl benzene silicone resin, and finally ultrasound the mixture 15min to form the final mixture.
2, coating process
first, the use of flat or micro-patterned PDMS as a substrate, and the use of UFO chemical bio-active treatment 90min. After resuscing, the 1mL coating mixture is deposited from a distance of 10cm with 210kPa compressed air by a spray gun and placed in a pre-baked 5min at 70C. The sample is then irradiated with UFO at 1h. Finally, triclosan (1H, 1H, 2H, 2H-perfluoroxyl) silane gas phase was deposited on the sample in an airtight container (Figure 2).
of fluorinated nanoparticles/adhesive coatings on 2 PDMS
structural symptomation and performance testing: the
authors conducted a series of symptomation and performance tests of sample performance.
1, SEM analysis
3 SEM image
SEM image coated with PDMS sample (Figure 3). The authors found that the coating has a layered structure of recessed geometry that helps support oil droplets for ultra-oiling. As can be seen from the micron-scale aggregates of nanoparticles and adhesives (Figure 3a), the first-level hierarchy has different sizes and shapes. In order to observe the concave geometry of the structure, an SEM image (Figure 3b) with a normal tilt angle of 70 degrees is used, which shows that nanoparticles and adhesives are usually combined into quasi-spherical shapes. In the second layer, nanoparticles and adhesives form micron-scale appendages that gather on the rough outer surface. Rough surfaces increase the number of cavitations, thus increasing the area of gas-liquid contact, thus increasing liquid repulsion.
2, surface wetting
various coatings measure the CA and TA values of water and cetane on flat and micro patterned PDMS (see Table 1). Untreated flat PDMS is slightly hydrophobic, with water CA at 113 degrees ±2 degrees and oil-averse xenane CA at 52 degrees ±2 degrees. By micro-patterned PDMS, roughness is introduced and its hydrophobic and oil-affinity is enhanced, resulting in water CA of 151 degrees ±3 degrees with ultra-hydrophobic and ultra-oil-affinity. Fluorosilane fluorinated by vapor deposition is added to the sample to reduce surface energy and improve oil resistance. On flat PDMS fluorine, the water CA is increased to 119 degrees ±2 degrees, which is almost the maximum CA that can be achieved on a flat surface, and xyneCA is increased to 69 degrees ±2 degrees. On fluorinated micro-patterned PDMS, water CA remains about the same as micro-patterned PDMS, much higher than the CA value on flat PDMS, and xenane CA is increased to 68 degrees ±2 degrees, with a simple micro-patterning, with nanoparticles/adhesive coating to obtain ultra-hydrophobic.
Table 1 A comparison of static contact and tilt angles of water and hexane droplets deposited on various coating planes and micro patterned PDMS
3, surface wear resistance
plane was studied by using friction wear tests Mechanical durability of fluorinated nanoparticles/adhesive coatings on PDMS, some of the optical images obtained from wear marks are shown in Figure 4, where the wear test produces observable abrasive marks after 100 cycles at 10mN.
Figure 4 Before and after the flat friction wear test
Figure 5 droplets at tilt angles before and after friction wear and vandalism
recorded hexane TA before and after the wear test, and TA on coating marks caused by scratching vandalism (Figure 5). Prior to the wear test, the hexane droplets that dragged over the surface of the substrate were completely unobstructed and slipped off the surface with a TA of 2 degrees ±1 degrees, and after the wear test, ta increased when dragged across the surface, and the hexane droplets were fixed at the defect, where the droplets slipped at the defect at TA of 5 degrees ±1 degrees. Droplets placed on defects ± slide at a time of 17 degrees TA. On a deliberately damaged coating, the hexane droplet becomes highly fixed, and regardless of the starting position of the droplet, the droplet requires a TA of 53 degrees ±4 degrees to slide down, and the coating is still able to reject the defect after a wear test, indicating that the coating has not been completely destroyed and that the coating is still wear-resistant.
4, surface transparency of the coating
Figure 6 Transparency contrast
the text is still readable when placed behind the coating on the flat and micro patterned PDMS (Figure 6).
conclusion:
Samuel Martin et al. coated PDMS with micro-patterned and hydrophobic SiO2 nanoparticles with adhesives of methyl-silica resins, and then deposited fluosilane on the coating phase, making the coating wear-resistant, ultra-hydrophobic, ultra-hydrophobic and transparent.
:
Martin, Samuel, and Bharat Bhushan. "Transparent, wear-resistant, superhydrophobic and superoleophobic poly (dimethylsiloxane) (PDMS) surfaces." Journal of colloid and interface science 488 (2017): 118-126.
Author: He Yi
Source: National Research Center for Coating Engineering and Technology