Oil-Infused Superhydrophobic Silicone Material for Low Ice Adhesion

Subscriber access provided by BOSTON UNIV

Article

Oil-Infused Superhydrophobic Silicone Material for Low Ice Adhesion with Long Term Infusion Stability Yong Han Yeong, Chenyu Wang, Kenneth J. Wynne, and Mool C. Gupta ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b11184 • Publication Date (Web): 31 Oct 2016 Downloaded from http://pubs.acs.org on November 3, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Oil-Infused Superhydrophobic Silicone Material for Low Ice Adhesion with Long Term Infusion Stability Yong Han Yeong1ψ, Chenyu Wang2, Kenneth J. Wynne2 and Mool C. Gupta1* 1

Charles. L. Brown Department of Electrical and Computer Engineering, University of Virginia,

Charlottesville, Virginia 22904, USA 2

Department of Chemical and Life Science Engineering, Virginia Commonwealth University,

Richmond, Virginia 23284, USA Email: ψ[email protected], *[email protected]

Keywords: superhydrophobic, oil-infusion, ice adhesion, anti-icing, micro-texturing

Abstract

A new approach for anti-icing materials has been created to combat the effects of ice accretion and adhesion. The concept combines the strengths of individual characteristics for low ice adhesion based on elasticity, superhydrophobicity and Slippery Liquid Infused Porous Surfaces (SLIPS) for an optimal combination of high water repellency and ice-phobicity. This was achieved by replicating micro-textures from a laser-irradiated aluminum substrate to an oilinfused polydimethylsiloxane elastomer, the result of which is a flexible, superhydrophobic and lubricated material. This design provides multiple strategies of icing protection through high water repellency to retard ice accretion, and with elasticity and oil-infusion for low ice adhesion in a single material. Studies showed that an infusion of silicone oils with viscosity at 100 cSt and

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

at below 8 wt% in PDMS solution is sufficient to reduce the ice shear strength to an averaged of 38 kPa while maintaining contact angles and roll-off angles of above 150° and below 10°, respectively. This ice adhesion value is a ~95% reduction from a bare aluminum surface and ~30% reduction from a micro-textured, superhydrophobic PDMS material without oil-infusion. In addition, 3-month aging studies showed that the wetting and ice adhesion performance of this material did not significantly degrade.

2


Page 2 of 36

Page 3 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1) Introduction Ice accretion and adhesion can occur in a variety of applications such as on power lines, aircrafts, wind turbines, refrigeration systems etc., resulting in decreased operating efficiencies and in some severe cases, catastrophic events with fatalities.1 Current ice mitigation strategies involve employing active anti-icing/de-icing solutions such as electro-thermal devices to heat a surface, use of chemicals or other mechanisms to physically crack and release the ice. While these methods succeed in reducing the impact of ice on the application, they are often associated with increased cost due to the weight and operating complexity. As such, researchers have been focusing on passive anti-icing solutions. The goal is to engineer a surface with inherently low ice adhesion strength, for easy removal by natural forces, such as wind, vibration or centrifugal force. The quest for such a surface has spanned over 70 years starting from the 1940’s with work focusing on tuning the surface chemistry of rigid, smooth coatings to reduce its surface energy.2 With the advancement of nanotechnology in the mid 1990’s and inspired by the lotus leaf, synthetic superhydrophobic surfaces were created for extreme water-repellency characteristics. Superhydrophobic surfaces rely on micro/nano textures on a low surface energy material to maintain air gaps between surface features that minimize the water-surface contact area with the formation of a Cassie-Baxter wetting state.3 This is in contrast to the Wenzel wetting state whereby water infiltrates the spaces between surface features for a fully-wetted surface.4 The effectiveness of superhydrophobic surfaces in reducing ice accretion and adhesion has been extensively studied with mixed results.5-12 Recently, a new strategy for ice-phobic surfaces designated “Slippery Liquid Infused Porous Surfaces” (SLIPS) was developed.13,14 SLIPS surfaces utilize porosity to trap a layer of immiscible lubricant to creates a liquid layer. Due to the lack of pinning spots on the surface and the slippage introduced 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

by the lubricant outer-layer, a water drop can slide across a SLIPS surface at low roll-off angles (ROA) for low ice adhesion.15,16 A schematic showing the surface morphology differences between a superhydrophobic and SLIPS surface is shown in Figure 1a and 1b. Numerous studies have been performed to investigate the effect of this lubricant layer on ice formation and adhesion with encouraging results.17-19 This concept has been extended by infusing lubricants into smooth, elastomeric materials. A combination of elasticity and the presence of the lubricant outer-layer provided a noticeable reduction in ice adhesion forces.20-23 For example, in recent work, Golovin et al.23 reduced the stiffness of a polydimethysiloxane (PDMS) by infusing an oillubricant resulting in ice adhesion strength of less than 20 kPa. These anti-icing surfaces rely on a variety of different surface attributes for ice mitigation. Kreder et al.2 and Sojoudi et al.24 have reviewed progress of these surface and categorized the different approaches. The classifications include topography (rough vs. smooth), liquid or not (dry vs. wet) and elasticity (soft vs. hard). Limitations in minimizing ice adhesion arise due to the wide variety of icing conditions that occur in nature. For example, superhydrophobic surfaces reduce ice adhesion only under Cassie-Baxter state ice accretion conditions.25 Under frost conditions, penetration of ice within the spacing of the surface micro/nano-textures occurs. This effectively increases the ice adhesion strength due to the increased surface area for the ice to inter-lock with.6,7,9-11,25-28 In addition, durability studies have shown that the tips of the micro-features could break off under repeated cycles of ice accretion and detachment.26,29 There is also concern over the longevity of the lubricant outer-layer for SLIPS surfaces. Studies have shown that the lubricant outer-layer could be depleted under high water shear conditions, high temperature evaporation or even carried away by other liquids.2,30-33 Moreover, water drops tend to impact and stick to a SLIPS surface,34 as compared to a complete rebound typically exhibited by superhydrophobic surfaces. This could 4


Page 4 of 36

Page 5 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


lead to undesirable ice accretion implications, especially under super-cooled drop impact icing conditions. The goal of this work was to create a new type of anti-icing material by leveraging the strengths of previous strategies. We focus on adapting characteristics found to contribute low ice adhesion within each classification defined by Kreder et al.2 and Sojoudi et al.24, and combining them to create an effective anti-icing material. Specifically, we chose to employ the “soft” characteristic from the elasticity category, the “rough” characteristic for topography and “wet” characteristic for “liquid extent”. We aimed to merge all these characteristics by infusing silicone oil in a micro-textured silicone elastomer. The presence of micro-textures on the inherently hydrophobic nature of silicone promotes superhydrophobicity. Oil infusion levels were optimized to avoid flooding the micro-textures, but rather provided a very thin layer following micro-texture contours. A schematic showing this concept is shown in Figure 1c. The rationale of this design is to provide multiple levels of ice accretion and adhesion protection. First, the superhydrophobic nature of the coating can promote the repellency of super-cooled water drops from adherence and nucleation on the surface, as shown by Mishchenko et al.35. Ice accretion under Cassie-Baxter conditions assures minimal contact area between ice and surface features for low ice release. For ice accretion under Wenzel-state conditions where ice forms within asperities of the surface, the presence of silicone oil on the micro-texture coupled with the elastic nature of the coating increases interfacial slippage, thereby promoting an ice detachment force low enough for release by commonly occurring natural forces such as vibration or wind.20 The fabrication of this flexible oil-infused superhydrophobic elastomer consisted of three steps, i.e. laser irradiation of an aluminum master to create micro-textures followed by the replication of micro-textures from the aluminum master to a virgin polycarbonate sheet via heat 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

embossing, and finally the transfer of the micro-textures onto a silicone material. The effect of oil infusion on the surface morphology, ice adhesion strength and surface wettability of the elastomer was systematically studied. Silicone oils of various viscosities (100, 500, and 1000 cSt) were infused into the silicone elastomer solution (after mixture of the base resin and curing components) at different infusion levels (2, 8, and 15 wt%. of the silicone solution), microtextured by replication from a laser-textured aluminum master and finally cured. Characterization of the material (wetting and surface morphology) were carried out the day after fabrication followed by ice adhesion measurements. The ice adhesion measurements were completed five days after sample fabrication. The samples were then aged for 3 months at room temperature conditions before the ice adhesion measurements were repeated. The optimal oil infusion level and viscosity was then elucidated. 2) Experimental Section 2.1) Fabrication of the Oil-Infused Micro-Textured Silicone Material A schematic showing the three fabrication steps is shown in Figure 2. Laser irradiation on an aluminum substrate (2.54 cm by 2.54 cm) was conducted with a 10 W, 532 nm wavelength pulsed ytterbium fiber laser system (Model YLP-G-10, IPG Photonics) with a 1.3 ns laser pulse width and a spot size of 25 µm. A galvanometer scanner (SCANcube 14, Scanlab) was used to scan the laser beam and onto the aluminum substrate. The laser scanning process is as follows: the averaged laser power was set at 3.9 µJ/pulse and linearly scanned across the aluminum substrate at a pulse repetition rate of 400 kHz and scan speed of 6 cm/sec. Upon reaching the end of the prescribed scan length (2.54 cm), the laser beam was moved horizontally by 14 µm and scanned at the same length in the reverse direction. This process was repeated until the entire 6


Page 6 of 36

Page 7 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


area of the aluminum substrate was laser micro-textured. Note that the distance of 14 µm was intentionally chosen to be smaller than the beam spot size so that the scan lines were partially overlapped, the result of which was a continuously micro-textured surface consisting of micropeaks and valleys. This technique of creating surface micro-textures was previously reported by Nayak et al.36,37 and Bhagat et al.38. A Scanning Electron Microscope (SEM) image of the lasertextured aluminum is shown in Figure 2. The second step was replicating the micro-texture of the aluminum master on a polycarbonate (PC) sheet. This intermediary step created a “negative” PC surface with microfeatures with low adhesion to silicone elastomer coatings. This step mitigated problems associated with high adhesion of aluminum to silicone.38 An industrial heat press (6” by 6” heat press, Hotronix) was utilized to emboss the aluminum master micro-features on the PC. A temperature (158 °C) slightly above the glass transition temperature of the PC (~147 °C) was chosen to facilitate embossing. The master was placed face down on the surface of a 1.58 mm thick PC substrate and supported by an aluminum piece before pressure was applied by the heat press. The force applied on the press was set to high (pressure of approximately 80 psi / 550 kPa) with a pressing time of 33 sec. The combination of the heat and force from the press resulted in the replication of the micro-features on the PC shown in Figure 2. The last step of the fabrication process involved transferring PC micro-textures to an oilinfused silicone elastomer material. Dow-Corning polydimethylsiloxane (PDMS, Sylgard 184) was used. The base resin and curing agent were mixed together in a 10:1 weight ratio and placed in a vacuum chamber to remove bubbles in the solution. Next, silicone oils of different viscosities (100, 500 and 1000 cSt, Clearco Products Co. & Dow Corning Xiamater PMX-series) were mixed separately into the PDMS solution (resin+curing agent). The amount of silicone oil 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

that were infused were varied at different levels, a low amount (2% wt. of PDMS solution), a medium (8% wt. of PDMS solution) and a high (15% wt. of PDMS solution). A pipette was used to dispense the PDMS-oil mixture on the textured PC substrate with a dispense volume adjusted for a 500 µm thick coating. The PDMS-oil mixture on the PC was then heat cured on a hot plate at 125 °C for 20 minutes. Finally, the resulting oil-infused, elastic micro-textured PDMS material was carefully peeled-off from the PC with a pair of tweezers. The material was adhered to an aluminum substrate using a silicone adhesive for ice adhesion tests. In addition to the oil-infused micro-textured material, micro-textured (superhydrophobic) and non-textured PDMS materials without oil infusion and non-textured PDMS materials with oil-infusion (resembling SLIPS surfaces) were fabricated to serve as control substrates for the ice adhesion test. The fabrication of these materials followed the same steps as outlined in Step 3 but with different types of dispensed PDMS solutions. For textured and non-textured PDMS materials without oil infusion, pristine PDMS solution was dispensed on textured and as-received (nontextured) PC sheets, respectively. In total, 14 different materials were produced for ice adhesion evaluation. It should also be noted that once Step 1 and 2 has been performed, the resulting micro-textured PC sheet could be repeatedly used for large quantity fabrication of micro-textured PDMS materials. This significantly simplifies the fabrication process and reduces the fabrication cost. 2.2) Sample Characterization The wettability of the micro-textured coatings was determined using a contact angle goniometer (Model 290, Ramé-Hart). A 10 µL water drop was used for a static contact angle (CA) measurement while a 20 µL water drop was used for the tilt measurement of the roll-off 8


Page 8 of 36

Page 9 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


angle (ROA). The larger drop size used for the ROA measurement is due to the wide range of substrate wettabilities that were fabricated. The size of a 20 µL water drop ensured that consistent ROA’s could be measured for all substrates for equal comparison of wetting effects on ice adhesion. Both CA and ROA measurements were repeated three times and at three different locations on the substrate to account for any variance in wettability performance. The characterization of the micro-textures of the substrates were performed using a SEM (Quanta 650, FEI) located in the Nanoscale Materials Characterization Facility (NMCF) at the University of Virginia. Imaging was performed in low-vacuum mode which allowed for characterization without sputter deposition of a conducting material. High-speed imaging of the drop impact and rebound from the oil-infused PDMS materials were conducted using a high-speed camera (SA-4, Photron) in the Fluids Research Innovation Lab at the University of Virginia. The substrate was tilted at 30° and a 10 µL water drop was dispensed at a height of approximately 11 cm above the substrate and allowed to impinge on the surface. The images of drop-surface interaction were recorded at 5000 frames/sec. 2.3) Ice Adhesion Test The ice adhesion test was conducted using a TA Instruments RSAIII dynamic mechanical analysis (DMA) instrument in the Department of Chemical and Life Science Engineering Virginia Commonwealth University. The principle of the test is based on a “static” ice accretion process whereby a resting body of water was allowed to cool and freeze on a sample. The accreted ice was then removed in a shear direction using a probe connected to a load cell. The maximum force that was required to release the accreted ice from the surface was recorded as the 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 36

ice detachment force. This method of ice adhesion test was previously used by Wang et al. in the evaluation of ice adhesion on pristine PDMS coatings.39,40 A plastic cylindrical mold (~2 cm height, ~0.75 cm diameter) was cut from the bottom end of a 1000 µL pipette tip and was placed vertically on the test substrates. Deionized water (200 µL) was dispensed into the plastic mold so that a surface area of approximately 0.75 cm in diameter was in constant contact with the water. This set-up was placed in a small commercial freezer set to -15 °C and allowed to freeze for 2 hr, after which an iced cylinder was formed on the substrate. The substrate with the ice cylinder was removed from the freezer and placed in the chamber of a DMA machine previously cooled to -10 °C with liquid nitrogen. This transfer process was timed to be less than 10 seconds. A duration of 2 minutes was allowed to pass for temperature equilibrium before the ice shear process began. A force probe positioned at 2 mm from the surface was moved at a speed of 0.05 mm/s to collide with the iced cylinder.41 The peak force to shear the iced cylinder from the substrate surface was recorded as the ice release force. Further details on the ice adhesion test set-up and calculation of the ice detachment force can be obtained from Wang et al.39,40 The test was performed for at least 6 times on each substrate and averaged to account for the variance in ice detachment force. The effect of aging of the substrates were also studied. After an initial round of ice adhesion tests, the substrates were placed in room temperature conditions for 3 months, after which a second round of ice adhesion measurements were conducted on the substrates. Similar to the initial round of tests, the experiment was performed for at least 6 times on each substrate. 3) Results and Discussion 3.1) Surface Morphology 10


Page 11 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3 shows the surface morphology of all the oil-infused micro-textured PDMS material. Regardless of the oil viscosity and infusion weight percentage, the micro-structures from the master aluminum were successfully replicated on the PDMS materials. These microfeatures create the necessary roughness on most of these inherently hydrophobic PDMS material to promote a Cassie-Baxter wetting state. For example, the averaged CA and ROA for a microtextured PDMS material without oil-infusion was 160.3° and 6.5°, respectively, which is indicative of a superhydrophobic surface.42 No visibly distinguishable surface morphology differences were found among superhydrophobic, micro-textured PDMS materials without oil infusion. Close inspection of the SEM images in Figure 3 reveal subtle differences in the surface morphologies caused by oil viscosity and percentage of oil-infusion. For surfaces infused with 100 cSt oil, the surface micro-textures were jagged with the presence of second-tier microfeatures regardless of the percentage of oil infusion (Figures 3a, b and c). For the 500 cSt and 1000 cSt oil-infused surfaces, the surface textures were slightly altered when infused at 8% and above. (Figures 3e and h) The second-tier surface features were diminished, and in general, the features were rounder and smoother than the 2% oil-infused cases. (Figures 3d and g) The alteration of the surface features were even more pronounced for surfaces infused with 15% oil. (Figures 3f and i) The second-tier micro-features were completely eliminated. In addition, the micro-features were short with rounded peaks and extremely interconnected with each other. This was most evident with the 15% 1000 cSt oil infusion material (Figure 3i). The surface morphologies of these oil-infused micro-textured materials have an impact of the wetting characteristics of the coatings, as discussed in the next few sections. 3.2) Ice Adhesion 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 36

The ice adhesion strength of the oil-infused, micro-textured PDMS materials at various oil infusion percentages and viscosity with its control substrates are shown in Figure 4. The control consisted of a smooth, pristine PDMS material without surface micro-textures. CA and receding angle (RCA) measurements of this smooth PDMS material revealed averaged values of 113.7° and 90°, respectively, which were in excellent agreement with previous work.40,43,44 In addition, a superhydrophobic PDMS material fabricated without oil-infusion was included in the ice adhesion measurement and analysis. Results showed that the ice detachment force for the smooth, control PDMS material (500 µm thick) was approximately 90 kPa on average, with a maximum detachment force recorded at 115 kPa. This was in good agreement with the values that were measured by Wang et al.40 who showed a thickness dependence of silicone elastomer materials for peak ice detachment force, and also conformed to Kendall’s theory45 for the removal of a rigid object from an elastomer. It should be noted that the ice detachment force for a rigid, poly(ethyl methacrylate) (PEMA) blended with a fluoropolymer (fluorodecyl POSS) was measured by Meuler et al. using a similar ice adhesion test set-up, to be ~250 kPa.44 Since the wetting characteristics of the rigid polymer coating (CA 122°, RCA 104°) was comparable to PDMS, one could infer that the surface energies of PDMS and the polymer coating were at similar levels. The fact that the ice detachment force for the rigid polymer coating was approximately 100 kPa higher than the smooth, PDMS material showed the advantage of using soft, elastomeric materials to counter ice adhesion. This is due to the large differences in moduli for ice and the elastomer coating, resulting in a mismatch in strain when placed under stress, leading to an easier removal of ice from the surface.40 The ice adhesion strength of the micro-textured, superhydrophobic PDMS material without oil infusion (Figure 4) was ~25 kPa lower than the smooth, control PDMS surface. 12


Page 13 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


However, there were large variances in the recorded ice detachment forces, e.g. the highest recorded detachment force was approximately 115 kPa, which was comparable to the values measured for the smooth, PDMS control material. This result suggest that ice accreted on the superhydrophobic material in a semi-Cassie/Wenzel wetting state with a partial penetration of ice in the micro-textures of the surface thus resulting in a larger surface area for the ice to interlock with. Previous work has shown that ice adhesion strength of superhydrophobic surfaces could vary significantly, depending on the wetting state of the surface during accretion and the degree of ice infiltration into the surface asperities.25,46 Results in Figure 4 also show that once infused with silicone oil, regardless of oil viscosity or level of infusion, the ice adhesion strength of the micro-textured PDMS materials decreased significantly as compared to the smooth, PDMS control sample and the superhydrophobic, micro-textured material without oil infusion. For example, even with a minimal infusion of 2% of the least viscous silicone oil (100 cSt), one could observe a significant reduction of ice detachment force from 89 kPa (smooth, PDMS control) to 46 kPa, an approximate 50% decrease. The reduction of force was also observed when compared to a superhydrophobic, micro-textured material without oil infusion (~30%). It should also be noted that this ice adhesion strength is approximately 95% lower than the ice adhesion strength of a bare aluminum surface (> 1000 kPa).15,22 The reductions were even more pronounced with increasing oil infusion percentage, to the point where the iced cylinder on a micro-textured material infused with the highest oil viscosity and infusion percentage (1000 cSt, 15%) could be removed by just a gentle touch of the finger. This drastic decrease in ice adhesion is attributed to the presence of silicone oil on the micro-features of the PDMS material, which can introduce additional slippage between the interface of ice and surface features.22,23 Therefore, even if ice was formed within the micro-features of the micro-textured material, the presence of 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 36

silicone oil is sufficient to reduce the bond between the ice and the micro-texture. A study of the trends in Figure 4 also indicated no significant effects of silicone oil viscosity on ice detachment force at 2% and 8% infusion levels. However, at the highest level of infusion (15%), there was a clear reduction of ice detachment force as the infused oil viscosities increased from 100 cSt to 1000 cSt. Although these results suggest an infusion of the micro-textured silicone materials at these high viscosities and levels to significantly reduce ice detachment force, drawbacks will be introduced. These drawbacks include a degradation of water repellency (decrease in CA and increase in ROA) which were further amplified when the samples were aged. This undesirable side-effect is further explained in the following section. It is worthwhile to note that no gradual increase of ice detachment force of the samples was observed from the first to the sixth ice adhesion test. 3.3) Wetting Characteristics The wetting characteristics of the oil-infused, micro-textured PDMS materials were studied in detail and results are shown in Figure 5. The CA and ROA for each of the coatings at different oil infusion levels and viscosities were plotted with its corresponding ice detachment force. These data points were represented by the solid lines and filled markers. In addition, the effect of material aging (3 months) on the wetting characteristics and ice detachment forces were measured and superposed in Figure 5 for comparison with the non-aged materials. Results show that initial micro-textured materials infused with 100 cSt silicone oil (Figure 5a) were superhydrophobic. All the surfaces had CA above 150° and ROA of less than 10° or less. This could be inferred from the SEM images shown in Figures 3a-c. The surface micro-textures of the material were preserved even at all levels of infusion, suggesting that the 14


Page 15 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


presence of silicone oil on the surface is minimal and did not affect the Cassie-Baxter wetting state. However, micro-textured materials infused with 500 cSt and 1000 cSt silicone oil exhibited wetting characteristics that differed with the 100 cSt coatings. At a low infusion level (2%), all materials remained superhydrophobic. But, once at or above 8% infusion, CA of the materials dropped below 150° with increased ROA above 20°. For example, the averaged CA and ROA of a micro-textured material infused with 15% 500 cSt silicone oil was measured to be 147.6° and 56.3°, respectively. The wetting performance further degraded for a micro-textured material infused with 15% 1000 cSt silicone oil. (CA of 142.3° and ROA of 63.9°) As shown with SEM images in Figures 3e, 3f, 3h and 3i, the peaks of these micro-textures were rounded and interconnected, indicating a “wavy” type of surface roughness profile that is not conducive towards maintaining a Cassie Baxter wetting state.47 In addition, the SEM images suggest a larger presence of silicone oil on the surface features. This was confirmed by visual inspection and touching of the material whereby oil residue would be left on the fingers. Effects from both the surface feature structure and presence of silicone oil contributed towards the formation of semi-Cassie/Wenzel wetting state, which led to the decreased CA and increased ROA. It is worthwhile to note that as an additional study, non-polar liquids such as silicone oil and toluene were used to measure the wettability on four oil infused micro-textured samples of different infusion viscosities and levels (100 cSt infusion at 2% and 8%, 500 cSt infusion at 2% and 8%). It was discovered that the liquids spread on all the samples, to the point where the wettability measurements could not be conducted. This showed that the oil-infused textured surfaces do not consist of the right surface chemistry and topology to repel liquids of low surface tension. With the exception of an outlier data point for 8% 1000 cSt oil infusion, aging effects did not significantly affect ice detachment force of the substrates (Figure 5c). However, the wetting 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 36

characteristics of certain oil-infused micro-texture materials were degraded. For example, for an oil-infused material of 15% 100 cSt oil, the averaged CA decreased from 154° to 144°, accompanied by an increase of averaged ROA from 11° to 34°. This degradation was even more severe for materials infused with 500 cSt and 1000 cSt silicone oils. The ROA for the surfaces infused with 8% of these oils degraded to the point of approaching drop pinning. This degradation is attributed to migration of silicone oil within the PDMS matrix to the surface. This effect was also previously observed by Zhu et al. in a non-textured silicone oil infused PDMS surface.22 Since this degradation was only observed after a 3-month aging, it could be determined that the migration occurs in a time scale of weeks. If the surface was physically abraded during the aging process, the silicone oil was thought to migrate to the surface to replenish the “lost” layer of oil. However, in our work, since the surfaces were not physically touched during the aging process, the oil migration resulted in an over-accumulation of surface silicone oil, partially filling the asperities and eventually resulting in a transition to a Wenzel wetting state. For high infusion levels (15%) of high viscosity (1000 cSt), the over-accumulation oil on the surface resulted in only the tips of the micro-features were visible in SEM images (Figure 6b). Therefore, the surface may be thought of as transitioning from a micro-textured, oil-infused material (Figure 1c) to an approximation of a SLIPS material (Figure 1b). This transition can be observed in Figure 5b and 5c for the 15% oil infusion cases, where the CA dramatically decreased to 110° with a sudden reduction in ROA from approaching pinning to 20° or less. These values are characteristic of SLIPS surfaces.34 It should be noted that the migration of silicone oil occurred for all samples, regardless of oil infusion viscosity and levels. However, the time scale for the migration is different for each oil viscosity. The rate of migration increases with increasing oil viscosities. 16


Page 17 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Since the ice detachment force for the materials highly saturated with silicone oil (e.g. 15% 1000 cSt infusion) was extremely low at less than 20 kPa, an additional study was performed to investigate if non-textured PDMS materials infused with silicone oils at lower percentages could result in equally low ice adhesion strength. As shown in Figure 7, the ice detachment force of micro-textured and non-textured PDMS materials infused with 1000 cSt silicone oil was studied. Results showed that at 2% and 8% infusion levels, the presence of the silicone oil on the surface of the material was not significant enough to reduce the ice adhesion strength below the levels of a micro-textured, superhydrophobic material without oil-infusion. It should be noted that the ice adhesion of the materials (of 2% and 8% infusion) were tested shortly after they were fabricated and not aged, therefore there was minimal migration of the oil from bulk to surface, resulting in the higher ice adhesion strength. At the highest level of infusion (15%), the ice adhesion strength was significantly reduced due to the large infusion of silicone oil which immediately migrated to the surface from bulk. This resulted in a large slippage between ice and surface. Presence of micro-texture or not, it is interesting to note that the 15% oil infused materials were found to have similar ice detachment forces (18 kPa). This suggests that an oil-infusion plateau for the micro-textured materials has been reached. Further amounts of oil infusion in the micro-textured materials would most likely offer no significant reduction in ice detachment force compared to the non-textured materials. The results showed that it is possible to infuse silicone oil into a micro-textured silicone elastomer material so as to combine the characteristics of elasticity, superhydrophobicity and slippage by oil infusion for ice accretion protection and low ice adhesion. The optimal oil viscosity and infusion parameters for long term infusion stability were found to be at 100 cSt and at 8% infusion level or less. The combination of the Cassie-Baxter wetting state for minimal 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 36

water-surface contact, and the presence of silicone oil for enhanced slippage, proved to be key toward the reduction of ice adhesion strength. It should be noted that the infusion of silicone oil can also further increase the flexibility of the silicone elastomer material to aid in ice release.23 However, the strong evidence of surface wettability changes with oil infusion, which also correlated with various ice adhesion levels shows that the flexibility effects from oil infusion is minimal. Findings showed that one could infuse the silicone elastomer at high infusions levels with highly viscous silicone oil for a maximum ice adhesion reduction, but the superhydrophobic wetting characteristics will be lost, and in some cases after aging, suffer from an overaccumulation of silicone oil on the coating surface which migrated from within the silicone elastomer. This results in a visibly oily and sticky coating which could attract foreign particles such as dust and hence rendering this coating impractical for use in applications. In comparison, micro-textured materials infused with 100 cSt oil are more stable even after an extended period of time. For example, Figure 8 shows that even after aging, a 10 µL water drop rebounded on impact from the aged 8%, 100 cSt oil-infused textured, PDMS material surface. The shape of the drop at impact and rebound compared favorably with previous work of Yeong et al.48 The low ice adhesion strength and superhydrophobicity features of this material could provide an attractive solution to current icing problems. For example, the material could be applied on a wind turbine or on an aircraft. The extreme water-repellency of the material could delay the event of ice accretion. Once ice accretion occurs, inherent forces such as centrifugal or aerodynamic forces could potentially release the ice from low ice adhesion surface. This material could also be used in a hybrid system where an active heating system could be employed on the oil-infused coating. The water-repellency and oil infusion could drastically reduce the heat required to prevent ice formation or for ice release. In addition, it should be the noted that the 18


Page 19 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


laser irradiation parameters of laser power, repetition rate, scan speed, etc. could be optimized to result in surface micro-textures with higher skewness, kurtosis or lower feature spacing. These characteristics have been identified by Kulinich and Farzaneh49 and Yeong et al.25 as features which could promote low ice adhesion strength under supercooled drop impact conditions. Superhydrophobic oil-infused materials with such surface features could be fabricated using techniques previously described for an ice adhesion strength that is potentially even lower than reported in this paper. 4) Conclusions An oil-infused, micro-textured silicone elastomer material was fabricated to achieve superhydrophobicity with reduced ice accretion and adhesion. The goal was to combine the individual icephobic characteristics of elasticity, water-repellency and oil-infusion into a single material. The micro-textures were first created by laser irradiation on aluminum master samples. Heat embossing methods were then used to replicate the micro-textures on a PC sheet before PDMS solution (base resin+curing agent) infused with silicone oil was dispensed on the microtextured polycarbonate sheet. Upon heat curing, the oil-infused silicone material was removed simply via a peel-off process. Silicone oils of various viscosities (100 cSt, 500 cSt and 1000 cSt) were infused into the silicone material at different levels (2%, 8% and 15% wt of PDMS solution) for the study of oil infusion effects on surface wettability and ice adhesion strength. Results showed an optimal combination of superhydrophobicity and low ice adhesion strength when 100 cSt silicone oil was infused at or below 8% levels in the micro-textured silicone material. CA and ROA values of the surface were above 150° and below 10°, respectively while the ice shear strength was measured to be a 38 kPa on average. This ice adhesion value was 19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 36

approximately 50% lower than a smooth, PDMS surface without oil infusion and approximately 30% lower than a superhydrophobic, micro-textured silicone material without oil infusion. These values did not significantly degrade even after an aging process of 3 months under room temperature conditions. Although infusion of more viscous silicone oils at high levels of infusion can further decrease the ice adhesion strength, the water repellency effect of the surface would be compromised. This was due to the migration of silicone oil molecules from within the elastomer to result in accumulated layer of lubricant on the surface of the material.

Acknowledgements The authors would like to thank the National Science Foundation (NSF) for sponsoring this work (Award: IIP 1343450). Kenneth Wynne thanks the School of Engineering Foundation and partial support from the National Science Foundation, Division of Materials Research, Polymers Program (DMR-1206259). The authors would also like to thank Prof. Eric Loth of the Fluids Research and Innovation Lab at the University of Virginia for the use its lab facilities for the wetting characterization and high-speed imagery of the materials.

20


Page 21 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References

(1) Kinnersley, S.; Roelen, A. The Contribution of Design to Accidents. Saf. Sci. 2007, 45, 3160.

(2) Kreder, M. J.; Alvarenga, J.; Kim, P.; Aizenberg, J. Design of Anti-Icing Surfaces: Smooth, Textured or Slippery? Nat. Rev. Mater. 2016, 1, 15003.

(3) Cassie, A.; Baxter, S. Wettability of Porous Surfaces. Trans. Faraday Soc. 1944, 40, 546551.

(4) Wenzel, R. N. Resistance of Solid Surfaces to Wetting by Water. Ind. Eng. Chem. 1936, 28, 988-994.

(5) Cao, L.; Jones, A. K.; Sikka, V. K.; Wu, J.; Gao, D. Anti-Icing Superhydrophobic Coatings. Langmuir 2009, 25, 12444-12448.

(6) Chen, J.; Liu, J.; He, M.; Li, K.; Cui, D.; Zhang, Q.; Zeng, X.; Zhang, Y.; Wang, J.; Song, Y. Superhydrophobic Surfaces Cannot Reduce Ice Adhesion. Appl. Phys. Lett. 2012, 101, 111603.

21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 36

(7) Farhadi, S.; Farzaneh, M.; Kulinich, S. Anti-Icing Performance of Superhydrophobic Surfaces. Appl. Surf. Sci. 2011, 257, 6264-6269.

(8) Jung, S.; Dorrestijn, M.; Raps, D.; Das, A.; Megaridis, C. M.; Poulikakos, D. Are Superhydrophobic Surfaces Best for Icephobicity? Langmuir 2011, 27, 3059-3066.

(9) Kulinich, S.; Farzaneh, M. On Ice-Releasing Properties of Rough Hydrophobic Coatings. Cold Reg. Sci. Technol. 2011, 65, 60-64.

(10) Momen, G.; Jafari, R.; Farzaneh, M. Ice Repellency Behaviour of Superhydrophobic Surfaces: Effects of Atmospheric Icing Conditions and Surface Roughness. Appl. Surf. Sci. 2015, 349, 211-218.

(11) Nosonovsky, M.; Hejazi, V. Why Superhydrophobic Surfaces Are Not Always Icephobic. ACS Nano 2012, 6, 8488-8491.

(12) Tourkine, P.; Le Merrer, M.; Quéré, D. Delayed Freezing On Water Repellent Materials. Langmuir 2009, 25, 7214-7216.

(13) Wong, T.; Kang, S. H.; Tang, S. K.; Smythe, E. J.; Hatton, B. D.; Grinthal, A.; Aizenberg, J. Bioinspired Self-Repairing Slippery Surfaces with Pressure-Stable Omniphobicity. Nature 2011, 477, 443-447.

(14) Sunny, S.; Vogel, N.; Howell, C.; Vu, T. L.; Aizenberg, J. Lubricant‐Infused Nanoparticulate Coatings Assembled by Layer‐by‐Layer Deposition. Adv. Funct. Mater. 2014, 24, 6658-6667. 22


Page 23 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Kim, P.; Wong, T.; Alvarenga, J.; Kreder, M. J.; Adorno-Martinez, W. E.; Aizenberg, J. Liquid-Infused Nanostructured Surfaces with Extreme Anti-Ice and Anti-Frost Performance. ACS Nano 2012, 6, 6569-6577.

(16) Wilson, P. W.; Lu, W.; Xu, H.; Kim, P.; Kreder, M. J.; Alvarenga, J.; Aizenberg, J. Inhibition of Ice Nucleation by Slippery Liquid-Infused Porous Surfaces (SLIPS). Phys. Chem. Chem. Phys. 2013, 15, 581-585.

(17) Chen, J.; Dou, R.; Cui, D.; Zhang, Q.; Zhang, Y.; Xu, F.; Zhou, X.; Wang, J.; Song, Y.; Jiang, L. Robust Prototypical Anti-Icing Coatings with a Self-Lubricating Liquid Water Layer between Ice and Substrate. ACS Appl. Mater. & Interfaces. 2013, 5, 4026-4030.

(18) Subramanyam, S. B.; Rykaczewski, K.; Varanasi, K. K. Ice Adhesion on LubricantImpregnated Textured Surfaces. Langmuir 2013, 29, 13414-13418.

(19) Ozbay, S.; Yuceel, C.; Erbil, H. Y. Improved Icephobic Properties on Surfaces with a Hydrophilic Lubricating Liquid. ACS Appl. Mater. & Interfaces 2015, 7, 22067-22077.

(20) Dou, R.; Chen, J.; Zhang, Y.; Wang, X.; Cui, D.; Song, Y.; Jiang, L.; Wang, J. Anti-icing Coating with an Aqueous Lubricating Layer. ACS Appl. Mater. & Interfaces 2014, 6, 69987003.

(21) Urata, C.; Dunderdale, G. J.; England, M. W.; Hozumi, A. Self-Lubricating Organogels (SLUGs) with Exceptional Syneresis-Induced Anti-Sticking Properties against Viscous Emulsions and Ices. J. Mater. Chem. A 2015, 3, 12626-12630.

23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 36

(22) Zhu, L.; Xue, J.; Wang, Y.; Chen, Q.; Ding, J.; Wang, Q. Ice-Phobic Coatings Based on Silicon-Oil-Infused Polydimethylsiloxane. ACS Appl. Mater. & Interfaces 2013, 5, 40534062.

(23) Golovin, K.; Kobaku, S. P.; Lee, D. H.; DiLoreto, E. T.; Mabry, J. M.; Tuteja, A. Designing Durable Icephobic Surfaces. Sci. Adv. 2016, 2, e1501496.

(24) Sojoudi, H.; Wang, M.; Boscher, N.; McKinley, G.; Gleason, K. Durable and Scalable Icephobic Surfaces: Similarities and Distinctions from Superhydrophobic Surfaces. Soft Matter 2016, 12, 1938-1963.

(25) Yeong, Y. H.; Milionis, A.; Loth, E.; Sokhey, J.; Lambourne, A. Atmospheric Ice Adhesion on Water-Repellent Coatings: Wetting and Surface Topology Effects. Langmuir 2015, 31, 13107-13116.

(26) Kulinich, S.; Farhadi, S.; Nose, K.; Du, X. Superhydrophobic Surfaces: Are They Really Ice-Repellent? Langmuir 2010, 27, 25-29.

(27) Meuler, A. J.; McKinley, G. H.; Cohen, R. E. Exploiting Topographical Texture to Impart Icephobicity. ACS Nano 2010, 4, 7048-7052.

(28) Zou, M.; Beckford, S.; Wei, R.; Ellis, C.; Hatton, G.; Miller, M. Effects of Surface Roughness and Energy on Ice Adhesion Strength. Appl. Surf. Sci. 2011, 257, 3786-3792.

24


Page 25 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(29) Wang, Y.; Xue, J.; Wang, Q.; Chen, Q.; Ding, J. Verification of Icephobic/Anti-Icing Properties of a Superhydrophobic Surface. ACS Appl. Mater. & Interfaces 2013, 5, 33703381.

(30) Smith, J. D.; Dhiman, R.; Anand, S.; Reza-Garduno, E.; Cohen, R. E.; McKinley, G. H.; Varanasi, K. K. Droplet Mobility on Lubricant-Impregnated Surfaces. Soft Matter 2013, 9, 1772-1780.

(31) Howell, C.; Vu, T. L.; Johnson, C. P.; Hou, X.; Ahanotu, O.; Alvarenga, J.; Leslie, D. C.; Uzun, O.; Waterhouse, A.; Kim, P. Stability of Surface-Immobilized Lubricant Interfaces under Flow. Chem. Mater. 2015, 27, 1792-1800.

(32) Wexler, J. S.; Jacobi, I.; Stone, H. A. Shear-Driven Failure of Liquid-Infused Surfaces. Phys. Rev. Lett. 2015, 114, 168301.

(33) Daniel, D.; Mankin, M. N.; Belisle, R. A.; Wong, T.; Aizenberg, J. Lubricant-Infused Micro/Nano-structured

Surfaces

with

Tunable Dynamic Omniphobicity at

High

Temperatures. Appl. Phys. Lett. 2013, 102, 231603.

(34) Cao, M.; Guo, D.; Yu, C.; Li, K.; Liu, M.; Jiang, L. Water-Repellent Properties of Superhydrophobic and Lubricant-Infused “Slippery” Surfaces: A Brief Study on the Functions and Applications. ACS Appl. Mater. & Interfaces 2015, 8(6), 3615-3623.

(35) Mishchenko, L.; Hatton, B.; Bahadur, V.; Taylor, J. A.; Krupenkin, T.; Aizenberg, J. Design of Ice-Free Nanostructured Surfaces Based on Repulsion of Impacting Water Droplets. ACS Nano 2010, 4, 7699-7707. 25



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 36

(36) Nayak, B. K.; Gupta, M. C. Self-Organized Micro/Nano Structures in Metal Surfaces by Ultrafast Laser Irradiation. Opt. Lasers Eng. 2010, 48, 940-949.

(37) Nayak, B. K.; Caffrey, P. O.; Speck, C. R.; Gupta, M. C. Superhydrophobic Surfaces By Replication of Micro/Nano-Structures Fabricated by Ultrafast-Laser-Microtexturing. Appl. Surf. Sci. 2013, 266, 27-32.

(38) Bhagat, S. D.; Gupta, M. C. Superhydrophobic Microtextured Polycarbonate Surfaces. Surf. Coat Tech. 2015, 270, 117-122.

(39) Wang, C.; Zhang, W.; Siva, A.; Tiea, D.; Wynne, K. J. Laboratory Test for Ice Adhesion Strength Using Commercial Instrumentation. Langmuir 2014, 30, 540-547.

(40) Wang, C.; Fuller, T.; Zhang, W.; Wynne, K. J. Thickness Dependence of Ice Removal Stress for a Polydimethylsiloxane Nanocomposite: Sylgard 184. Langmuir 2014, 30, 1281912826.

(41) Hejazi, V.; Sobolev, K.; Nosonovsky, M. From Superhydrophobicity to Icephobicity: Forces and Interaction Analysis. Sci. Rep. 2013, 3, 2194.

(42) Feng, X.; Jiang, L. Design and Creation of Superwetting/Antiwetting Surfaces. Adv. Mater. 2006, 18, 3063-3078.

(43) Mata, A.; Fleischman, A. J.; Roy, S. Characterization of Polydimethylsiloxane (PDMS) Properties for Biomedical Micro/Nanosystems. Biomed. Microdevices 2005, 7, 281-293.

26


Page 27 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(44) Meuler, A. J.; Smith, J. D.; Varanasi, K. K.; Mabry, J. M.; McKinley, G. H.; Cohen, R. E. Relationships Between Water Wettability and Ice Adhesion. ACS Appl. Mater. & Interfaces 2010, 2, 3100-3110.

(45) Kendall, K. The Adhesion and Surface Energy of Elastic Solids. J. Phys. D 1971, 4, 1186.

(46) Susoff, M.; Siegmann, K.; Pfaffenroth, C.; Hirayama, M. Evaluation of Icephobic Coatings—Screening of Different Coatings and Influence of Roughness. Appl. Surf. Sci. 2013, 282, 870-879.

(47) Bottiglione, F.; Carbone, G. Role of Statistical Properties of Randomly Rough Surfaces in Controlling Superhydrophobicity. Langmuir 2012, 29, 599-609.

(48) Yeong, Y. H.; Burton, J.; Loth, E.; Bayer, I. S. Drop Impact and Rebound Dynamics on an Inclined Superhydrophobic Surface. Langmuir 2014, 30, 12027-12038.

(49) Kulinich, S.; Farzaneh, M. How Wetting Hysteresis Influences Ice Adhesion Strength on Superhydrophobic Surfaces. Langmuir 2009, 25, 8854-8856.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figures

Figure 1. A schematic that compares (a) superhydrophobic surface (b) slippery liquid infused porous surfaces and (c) an oil-infused, micro-textured superhydrophobic elastomer. 28


Page 28 of 36

Page 29 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Schematic showing the steps of fabrication for the oil-infused, micro-textured PDMS material.

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 36

Figure 3 SEM images of the oil-infused micro-textured PDMS materials. (a)-(c) shows 100 cSt oil infusion at 2%, 8% and 15% wt., respectively; (d-f) shows 500 cSt oil infusion at 2%, 8% and 15% wt., respectively and (g-i) shows1000 cSt oil infusion at 2%, 8% and 15% wt., respectively.

30


Page 31 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. A comparison of ice adhesion strength of the oil-infused, micro-textured PDMS materials at various oil viscosities (100-1000 cSt) and infusion levels (2-15% wt.) with a smooth, PDMS control material and a superhydrophobic, textured PDMS material without oil infusion.

31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 5. Wetting characteristics and ice adhesion strength of oil-infused, micro-textured PDMS materials at various levels of oil viscosities and infusion. The wetting and ice adhesion performance of aged samples (3 months) are also included and represented by open markers and 32


Page 32 of 36

Page 33 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


dashed lines. (a) shows results for 100 cSt oil-infused materials; (b) shows results for 500 cSt oilinfused materials and (c) shows results for 1000 cSt oil-infused materials.

Figure 6. SEM images showing the surface micro-texture morphology changes in the oil-infused materials when aged for 3 months. (a) shows the morphology of PDMS material infused with 15% 100 cSt oil and (b) shows the PDMS material infused with 15% 1000 cSt oil.

33



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 7. Ice detachment force for 1000 cSt oil-infused micro-textured and non-textured PDMS materials.

34


Page 34 of 36

Page 35 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 8. Sequence of images acquired by high-speed imaging showing a 10 µL water drop impacting and rebounding from an aged 8%, 100 cSt oil-infused micro-textured PDMS material inclined at 30°.

35



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

TOC Graphic

36


Page 36 of 36

Oil-Infused Superhydrophobic Silicone Material for Low Ice Adhesion

Recommend Documents