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SCIENCE ADVANCES | RESEARCH ARTICLE APPLIED SCIENCES AND ENGINEERING Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant Meirong Song,1,2,3 Jie Ju,1 Siqi Luo,2 Yuchun Han,2 Zhichao Dong,1* Yilin Wang,2* Zhen Gu,1 Lingjuan Zhang,1 Ruiran Hao,1 Lei Jiang1* 2017 © The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC) INTRODUCTION Pesticide spraying is “hard” agricultural work, where more than 50% of agrochemicals are lost because of undesired bouncing and splashing behaviors on crop leaves with “waterproof” properties (1–3) In natural plants, superhydrophobic leaves are ubiquitous, and they usually get their nonwetting properties from the presence of waxy features on their surface Particularly because of the combination of extremely low energized chemical composition and microstructured/nanostructured surface morphology, the superhydrophobic surface was demonstrated to facilitate droplets, even those with surfactant additives (4), bouncing and splashing within shortened contact time (5–17) This increases the difficulty of droplet retention (18), thus threatening ecological security and human safety: If pesticides cannot be properly deposited on crops, then pests might not be controlled and plant injury might occur (1) Redundant pesticides might contribute to soil, air, or water pollution, and human health might be negatively affected Although adding surfactants to the sprayed liquid is considered to be a simple method to reduce surface tension and to improve drop retention on a smooth hydrophobic surface, surfactant liquids still slide or bounce off the hydrophobic surface at a tilted angle and reduce liquid splashing on the superhydrophobic surface (19) In addition, according to the Kelvin-Helmholtz instability, the wave number kmax equals 2raU2/3g, where is the air density, g is the fluid surface tension, and U is the relative velocity between gas and liquid Therefore, reduced surface tension was believed to play a major role in the increased instability of the spilt droplet (20, 21) Enhancing liquid deposition on the superhydrophobic surface is complex and difficult work, where selected surfactants need to diffuse from the bulk to the newly created interfaces quickly, because the contact time is typically only several milliseconds, and need to decrease retraction velocity to reduce instability due to the reduced surface tension Several studies have demonstrated the difficulty of surfactant drop deposition on the super1 CAS Key Laboratory of Bio-inspired Materials and Interfacial Science, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China 3College of Sciences, Henan Agricultural University, Zhengzhou, Henan 450001, China *Corresponding author Email: dongzhichao@iccas.ac.cn (Z.D.); yilinwang@iccas.ac.cn (Y.W.); jianglei@iccas.ac.cn (L.J.) Song et al Sci Adv 2017; : e1602188 March 2017 hydrophobic surface On the basis of these results, it would seem that surfactant additives should not be responsible for reducing high-speed liquid splashing on the superhydrophobic surface However, we found that this kind of “unavoidable” bouncing or splashing behavior was greatly inhibited or even completely reduced on the superhydrophobic surface at varied angles by adding a small amount of a double-chain vesicle surfactant Unlike the micelle surfactant previously discussed, the vesicular surfactants additive demonstrated here was able to diffuse from the bulk to the newly formed interfaces during the deformation process, enter into the microstructured/nanostructured morphology, confine the motion of the liquid with the help of the wettability transition during the first inertial spreading stage of ~2 ms, decrease the retraction velocity down to nearly zero, and reduce bouncing and splashing (Fig 1) For the first time, we have found that the vesicle surfactant could exhibit a distinguished ability to alter the surface wettability during the impact process By taking advantage of this wettability transition, not only have liquid splashing and retraction been completely reduced but the maximum wetting area is also maintained after the impact process This behavior is different from that observed in previous research, in which a micelle surfactant drop could bounce off the superhydrophobic surface (18), viscosity induced the splashing reduction (1), a surfactant drop partly reduced the liquid retraction on the hydrophobic surface (22–24), and nanoparticles or surface charges suppressed droplet rebound on the superhydrophobic surface (19, 25) RESULTS Figure shows the impacts of droplets of pure water and aqueous solutions containing the same mass fraction of the micelle surfactant sodium dodecyl sulfate (SDS), trisiloxane molecules (TSs), and the vesicle surfactant sodium bis(2-ethylhexyl) sulfosuccinate [Aerosol OT (AOT)] on a Brassica oleracea L leaf (Fig 1A) at a velocity of 2.53 ± 0.11 m s−1 using high-speed cameras (movie S1) In the experiment, the impact behavior was defined by measuring more than 30 different positions of the same sample and surfactant solutions The B oleracea L leaf surface characterized by microstructured/nanostructured morphologies (Fig 1, B and C) shows a water contact angle of 156.2 ± 4.3° (Fig 1D), ensuring superhydrophobicity The impacting water droplet, after reaching its maximum spreading at ~1.8 ms, breaks up into numerous droplets of Downloaded from http://advances.sciencemag.org/ on March 2, 2017 Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface SCIENCE ADVANCES | RESEARCH ARTICLE (Fig 1E) By adding a certain amount of surfactants, the receding splash be inhibited by varying degrees (movie S1) Figure (F and G) shows that aqueous droplets containing 1% SDS or 1% TSs partially reduced the receding splash but left several streams during retraction and finally broke up into several fragments In contrast, by adding 1% AOT in the aqueous phase, the impacting drop first spread to a larger wetting area within ms Then, the liquid broke up and the receding laminar stream was substantially depressed (Fig 1H) even after the maximum spreading stage (movie S1) Finally, a large wetting area was achieved and maintained Partial and scarce receding behavior at low-speed impact was found in the micelle and vesicle regions (fig S1), respectively Furthermore, on artificial superhydrophobic surfaces with varied structures and tilted angles, aqueous droplets containing 1% AOT would spread properly (movies S2 to S4) Notably, this kind of liquid deposition behavior is in contrast to previous works, where surfactant drops have been shown to bounce off the superhydrophobic surface (18), although surfactants can help the liquid wet the hydrophobic surface (movie S5) (25) AOT is therefore a unique surfactant that has a more pronounced effect than the others in controlling liquid deposition and in reducing unavoidable splash Song et al Sci Adv 2017; : e1602188 March 2017 DISCUSSION Compared with the mechanism of liquid deposition enhancement using polymer additives (1), surfactant additives cannot alter viscosity but can reduce the liquid’s surface tension Although surfactants can decrease the surface tension of the liquid, helping it spread on a hydrophobic surface under a low-speed impact (25), the reduction of surface tension also plays a major role in the increased instability and the enhanced droplet’s splash (20, 21) According to the KelvinHelmholtz instability, kmax = 2raU2r/3g, the key to reducing instability is via the retraction velocity Ur, and the brevity of impact contact time should be enough for liquid droplets to wet the superhydrophobic surface (18) In our experiment, local pinning is observed for SDS (Fig 1F) and TSs (Fig 1G), and the entire pinning is found for AOT in the peripheral area of maximum spreading (Fig 1H), where the retraction velocity Ur slows down to a low value, resulting in a small kmax For the AOT drop, the motion of spreading is greatly confined, leading to extremely low instability and thus retarding the splash (movie S1) The exceptional molecular structure of AOT distinguishes it from the other two surfactants in reducing splash and in enhancing liquid deposition Cryo-TEM (transmission electron microscope) imaging of Downloaded from http://advances.sciencemag.org/ on March 2, 2017 Fig The deposition of high-velocity impacting drops on the superhydrophobic leaf surface (A) Optical image of the B oleracea L leaf (B and C) Environmental scanning electron microscope (SEM) images of the leaf surface with a microstructured/nanostructured morphology (D) Water contact angle reveals the superhydrophobic property of the leaf surface (E) Impact process of a water droplet on the superhydrophobic leaf surface The splashing of water mainly occurs in the receding stage (F and G) Inhomogeneous receding behavior: SDS (1%) and TS (1%) additives partially inhibit the receding splash (H) Reduced receding behavior by the AOT surfactant: The receding splash was substantially depressed by 1% AOT additive SCIENCE ADVANCES | RESEARCH ARTICLE property reflected in the diffusion coefficients achieved through 1H nuclear magnetic resonance (NMR) spectrometry (fig S2) and dynamic contact angles (fig S3), the DST results indicate that AOT has the fastest diffusion speed to the air/water interface and thus has the strongest ability to reduce the surface tension when there are newly created surfaces Besides reducing splashing on natural superhydrophobic leaves, AOT is the most effective surfactant that inhibits the bouncing and splashing of the liquid drops on the artificial superhydrophobic surface at both low (~1.2 m s−1) and high (~2.5 m s−1) impact speeds The artificial superhydrophobic surfaces include a microstructured/ nanostructured superhydrophobic surface composed of 20-nm hydrophobic SiO2 nanoparticle composites with a typical size and spacing of around 200 nm and a CuO nanosheet structured superhydrophobic surface with a typical size of about to mm in length and 200 to 600 nm in width The water contact angles of these artificial superhydrophobic surfaces are 161.3 ± 0.5° and 159.1 ± 1.7°, respectively, which are much higher than those of the natural B oleracea L leaf A fluorinated glass slide with a water contact angle of 112.8 ± 1.1° is Fig The molecular structure, dynamic surface tension, and impact behavior of SDS, TSs, and AOT (A1 and B1) Cryo-TEM images of both 1% SDS and 1% TSs show the micelle aggregates at a mass fraction of 1% (C1) Cryo-TEM image of 1% AOT shows that multilamellar vesicles have formed, indicating the dense aggregates of AOT molecules at the air/water interface (A2) SDS has a long chain, and its dynamic surface tension (DST) slowly falls in the rapid fall region and cannot reach its equilibrium within a surface age of 100 ms (A3) The droplets containing SDS are easy to rebound on the superhydrophobic surface even for highly concentrated solution (B2) TSs have long induction periods in the first tens or hundreds of seconds (B3) With the increase of the concentration, the induction period is shortened so that the impact behavior turns from bouncing, emission, to no rebound On the inclined surface, it is still easy to partially rebound (C2) AOT distinguishes itself from other surfactants in the fastest diffusion speed to form a densely packed molecular layer at the air/water interface AOT directly approaches low surface tension of around 32 mN/m at the very beginning of the bubble pressure measurement, showing the lowest DST among the three surfactants within a surface age of 80 ms The DSTs of 1% SDS and 1% TSs begin nearly at the same value of ~43 mN/m TS quickly decreases to a lower value, and SDS slowly decreases to a higher value (C3) AOT is the most effective surfactant that inhibits bouncing of the liquid drops on the superhydrophobic surface Song et al Sci Adv 2017; : e1602188 March 2017 of Downloaded from http://advances.sciencemag.org/ on March 2, 2017 was used to prove our assumption, which was achieved by allowing a free-falling surfactant drop to impact the Cu mesh followed by immersion in liquid nitrogen This mimics the surfactant packing stage during the impact process The significant differences of the surfactant aggregates are shown in Fig (A1 to C1), where the multilamellar vesicles were closely packed at the air/water interface for the AOT drop with a mass fraction of 1%, whereas micelles only randomly and loosely existed for the other two surfactant solutions at the same mass fractions Compared with the sample molecular structures of SDS, TSs, and the previously mentioned surfactants in reducing the liquid bouncing (18, 25), AOT has two alkyl chains and a relatively small hydrophilic head group This particular molecular structure of AOT is the main reason for its compact and directed alignment and leads to the multilamellar vesicle structure (26) As shown in Fig (A2 to C2), among the three surfactants, the aqueous solution containing 1% AOT exhibits the lowest DST within a surface age of 80 ms At the beginning of the bubble pressure measurement of ~10 ms, its DST could decrease to a low value of ~32 mN/m (Fig 2C2), whereas both 1% SDS and 1% TSs have DSTs that begin in a high value of ~43 mN/m (Fig 2, A2 and B2) Similar to the SCIENCE ADVANCES | RESEARCH ARTICLE Fig Schematic illustration for splash inhibition on the superhydrophobic surface by surfactant additives (A) The impacting water drop mainly breaks up in the receding stage after spreading to the maximum lamellar liquid The upward increased capillary force induced by the squeezed air entrapment in the nanostructure easily makes the water drop take off the surface (B) For the surfactants in the micelle region, the surfactant molecules cannot replenish the newly created air/water interface (high DST), and the surface tension of the deformed drop is not uniform, explaining the nonuniform receding behavior The nonuniform surface tension leads to partial wettability transition, and several scattered fragments stick on the substrate as SDS, TSs, and AOT in the micelle region The reduced surface tension makes the entry of the impacting drop in the nanostructure much easier because of the reverse of capillary force (C) Because of the lowest DST and dense aggregates at the air/ water interface, AOT in the vesicle region effectively saturates the newly created surface within a short time and maintains a homogeneous low surface tension at the air/liquid/solid interface so that it can change the surface wettability as long as the drop contacts the surface, thus leading to hardly receding behavior and a large wetting area Song et al Sci Adv 2017; : e1602188 March 2017 drop would break up into multiple droplets during the receding state and would splash in the final state (Fig 1E) For the surfactant drops, if the surfactant molecules cannot replenish the newly created air/ water interface in time, typically with high DST, then the surface tension of the deformed drop could not be uniform, where nonuniform receding behavior occurs (Fig 3B) Examples can be found for the SDS drop (Fig 1F), the TS drop (Fig 1G), and the AOT drop in the micelle region (fig S4) In contrast, if the surfactant with a low beginning DST can effectively saturate the newly created surface within ~1.8 ms (corresponding to the spreading time) and maintain the homogeneous low surface tension at the air/liquid/solid interface, then the liquid can uniformly deposit on the superhydrophobic surface (Fig 3C) As shown in Fig 1H and fig S4, a gentle and uniform receding contact line will be obtained similar to AOT in the vesicle region These results provide direct evidence for the role of AOT in controlling the receding splash The underlying mechanism for the abovementioned transient knockdown of the receding velocity at the pinning area can be ascribed to the wettability transition in the spreading phase At the peripheral area of maximum spreading, the impacting water drop slides over air cushions that are trapped on or beneath the superhydrophobic surface, and it is difficult for the water to enter the nanostructures (Fig 3A) The upward increased capillary force induced by the squeezed air entrapment in the nanostructures easily makes the water drop take off the surface (28) Similar behavior is observed for the micelle surfactant drops (Fig 3B) The final “floating” state of the micelle surfactant drop, the 0.1% AOT drop, indicates that micelle surfactant drops could not properly reverse surface wettability, which can be seen from the cryo-SEM image in fig S5 In contrast, the reduction of surface tension induced by the vesicle surfactant leads to the dropdown, reverses the capillary force, and makes an easier and deeper entry of the impacting drop in the nanostructure (the side view in spreading state in Fig 3C) Cryo-SEM was used to prove the reverse of surface wettability during the impact, where the vesicle surfactant drop (1% AOT drop) is trapped between the gaps of nanoneedles and fully wets the nanostructured superhydrophobic surface (fig S5) The outward hydrophobic tails of the surfactants at the air/liquid interface act as bridges to connect the drop and the nanostructure by hydrophobic force and to change the wettability of the superhydrophobic surface Through this process, the surfactant droplets can be pinned and thus reduce the receding velocity via the wettability transition at the peripheral area of maximum spreading As a result, the high-speed impacting AOT drops can firmly and quickly deposit on the superhydrophobic surface The wettability transition at the central contact point is easier than at the peripheral area because capillary forces are overcome by inertial effects (29) at a high Weber number regime (We > 200) Both the water drop and the surfactant drop tend to become convex in the nanostructure of the superhydrophobic surface because of the downward hammer pressure and the dynamic pressure (8) However, the water repellency of structure chemistry and the huge upward Laplace pressure induced by the squeezed air entrapment in the nanostructure rebound the water drop, as shown in Fig 1E AOT also manifests itself in inhibiting rebound and splash on tilted superhydrophobic surfaces Superhydrophobic surfaces with tilted angles of 30o, 60o, and 75o are used In the experiment, the SDS shows little effect on the liquid deposition within the tested concentration region (Fig 2A3), although it is a good choice to inhibit rebound on the hydrophobic surface, as shown in movie S5 (15, 16, 23) The TS of Downloaded from http://advances.sciencemag.org/ on March 2, 2017 also used for comparison As shown in movie S5, although the droplets containing SDS can properly deposit on a smooth hydrophobic surface, it is difficult to reduce the rebound on a superhydrophobic surface, no matter how low or how high the impact speed is, even for highly concentrated solutions For TSs, with the increase in concentration, the induction period is shortened so that the low-speed impact behavior turns to emission from bouncing, whereas it is still easy to partially rebound after a high-speed impact In contrast, for AOT, the liquid droplets can deposit on the hydrophobic surface at a low concentration of 0.1% and at any superhydrophobic surfaces with a concentration of 0.3% (movie S5) A diagram is shown in Fig to explain how the receding splash can be substantially depressed by AOT Driven by the inertia, the impacting liquid first spreads to a maximum diameter (27) As shown in the spreading state of the diagram, the liquid droplet experiences a large surface deformation during the high-speed impact, and the curved edge of the spreading drop is completely out of equilibrium when it reaches its maximum diameter Then, surface tension acts on the liquid to retract the flow above the substrate For water, the SCIENCE ADVANCES | RESEARCH ARTICLE drop shows the impact behavior from bouncing, emission, to no rebound as the concentration increases from 0.01 to 1%, but it still rebounds partially on the oblique superhydrophobic surface (Fig 2B3) The percentage of liquid that bounces off the surface can be quantitatively measured through an analytical microbalance, and the impact processes of surfactant drops on the horizontal and tilted superhydrophobic surfaces are shown in movie S3 Only AOT can suppress the rebound of aqueous droplets on both horizontal and oblique surfaces at a low mass fraction of 0.3% at any inclined angles (Fig 2C3) Figure S1 depicts the impact behaviors of aqueous drops containing the AOT additive in three regions At concentrations lower than the critical micelle concentration, complete bouncing occurs along with complete receding behavior At the micelle region, partial receding of the contact line is accompanied with partial splashing, partial rebound, and no rebound Scarce receding of the contact line takes place only at the vesicle region, indicating that both the rebound and receding splashes have been greatly inhibited CONCLUSION In conclusion, although we have mainly focused on a specific microstructured/nanostructured superhydrophobic surface with varying tilted angles to elucidate the role of the vesicle surfactant (AOT) in inhibiting the receding splash, the scarce or gentle receding behavior can also be generalized to apply to other artificially fabricated superhydrophobic surfaces and other single-drop impact and spray processes at varied impact velocities (Fig and movies S6 to S9) In addition, AOT is shown to be a stable surfactant molecule (fig S6) This work helps advance our understanding of how to control liquid deposition on superhydrophobic surfaces Therefore, this approach Downloaded from http://advances.sciencemag.org/ on March 2, 2017 Fig The splash inhibition of vesicle AOT generalizes to other superhydrophobic surfaces (A1 and A2) SEM images of silicon nanowire–arrayed surface from top and side views (C1 and C2) SEM images of patterned superhydrophobic surfaces with arrayed silicon micropillars and nanowires from top and cross-sectional views (E and G) SEM images of the microstructured/nanostructured superhydrophobic SiO2 surface and the superhydrophobic CuO surface with nanoneedles (B1, D1, F1, and H1) The impacting water drop makes a big splash on superhydrophobic surfaces (B2, D2, F2, and H2) The receding splash is greatly inhibited by 1% AOT on these superhydrophobic surfaces The impact velocity of each impacting drop is 2.53 ± 0.11 m s−1 Song et al Sci Adv 2017; : e1602188 March 2017 of SCIENCE ADVANCES | RESEARCH ARTICLE silicon plate was O2 plasma–treated and then put in a sealed container together with a piece of glass coated with 0.5 ml of (heptadecafluoro1,1,2,2-tetradecyl)trimethoxysilane for hours at 80°C MATERIALS AND METHODS Characterization Analysis of the droplet deposition on the B oleracea L leaf surface and superhydrophobic substrates was recorded with i-SPEED (Olympus) high-speed cameras from the oblique view and a FASTCAM Mini UX100 (Photron) from the side view, respectively SEM images were obtained using a field-emission SEM at 10 kV (Hitachi S-4800) The images of cryogenic electron microscopy were carried out using a fieldemission SEM (Hitachi S-4300) equipped with extra low–temperature equipment at kV (cryo-electron microscope, Leica) Cryo-TEM images were obtained with FEI Tecnai Spirit BioTwin TEMs Cryotransfer holders were used to ensure low-temperature transfer and observation of frozen hydrated specimens Contact angles were measured using a contact angle measurement device (OCA 20, DataPhysics), with droplets of ml to be removed dynamically Each reported contact angle was an average of at least five independent measurements The diffusion rates were determined with a Bruker AVANCE 600 NMR spectrometer The DSTs were carried out with an automatic maximum bubble pressure tensiometer (Krüss BP100), which measures the behavior of a surfactant over a wide speed range as part of a single, fully automatic measuring process and determines surface tension as a function of surface age The measured range in the time window is from 10 ms to 10 s The capillary diameter is 0.210 mm Superhydrophobic silicon nanowire structures A silicon wafer was cleaned with acetone, ethanol, and deionized water before it was immersed in weight % hydrofluoric acid solution for to remove the oxidation layer Then, it was put in a mixed solution of 4.8 M hydrofluoric acid and 0.5 mM silver nitrate for to deposit silver seed on the substrate It was successively immersed in a solution of 4.8 M hydrofluoric acid and 0.15 M hydrogen peroxide for 30 to realize metal-assisted etching of silicon, which resulted in the acquisition of silicon nanowire structures The typical length of the nanowire was ~1.2 mm, and the space between nanowires was about 50 nm The as-prepared silicon plate was O2 plasma–treated at 150 W for 30 s and then put in a sealed container together with a piece of glass coated with 0.5 ml of (heptadecafluoro-1,1,2,2-tetradecyl)trimethoxysilane The container was evacuated with a vacuum pump After hours at 80°C, the plate showed surface superhydrophobicity with a contact angle of 154.5 ± 3.2° Microstructured/nanostructured SiO2 surface The commercial glass plates were cleaned with acetone, ethanol, and deionized water In accordance with our previous research (30), the polymer-particle dispensed solution was prepared by adding ml of Capstone ST-200 (DuPont Co.) solution and g of hydrophobic fumed silica nanoparticles (average particle size of 14 nm; Evonik Degussa Co.) in ml of acetone and 20 ml of ethanol The solution was mixed and stirred for 30 in a closed bottle Precleaned glass plates were dipped in this solution at a speed of 80 mm s−1 and pulled out from the solution at a speed of 100 mm s−1 Owing to the rapid evaporation of the solvent, the semitransparent membrane quickly transformed into a white coating with extremely high water repellency From an SEM observation, the aggregate of SiO2 nanoparticles had random features of typical size and spacing of around 200 nm Superhydrophobic CuO nanosheets The copper plate was first cleaned with acetone, ethanol, and purified water before modification It was then immersed in a solution of 0.15 M ammonium persulfate and 2.5 M sodium hydroxide for 20 and subsequently immersed in a 0.1 M perfluorodecanoic acid solution for hour The prepared CuO nanosheets were about to mm in length and 200 to 600 nm in width After the copper plate was rinsed with distilled water and dried with N2, it showed a high water repellency with a contact angle of 159.1 ± 1.7° Patterned pillar-structured silicon substrate Silicon wafers (n-type doped with phosphorus, -oriented, 525 mm thick) were patterned using standard photolithography techniques A thin layer of positive resist was spray-coated onto the silicon wafer at a rotational speed of 3000 rpm, which was followed by an ultraviolet (UV) exposure process (Karl Suss MA6) Then, the UV-exposed Si wafer was immersed in the resist developer to remove the unexposed photoresist Subsequently, deep reactive ion etching was performed Micropillar has a diameter of 10 mm, a space of 10 mm, and a height of 20 mm After the substrates were resist-stripped (Microposit Remover 1165), they were cleaned with ethanol and acetone before the chemical modification process was performed The as-prepared Song et al Sci Adv 2017; : e1602188 March 2017 SUPPLEMENTARY MATERIALS Supplementary material for this article is available at http://advances.sciencemag.org/cgi/ content/full/3/3/e1602188/DC1 fig S1 Scarce receding of drop-substrate contact line for the AOT drop fig S2 Diffusion coefficient 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nanostructured superhydrophobic surfaces at low and high speeds movie S6 Water spray impact on horizontal superhydrophobic surface movie S7 Water spray impact on tilted superhydrophobic surface movie S8 AOT (1%) spray impact on horizontal superhydrophobic surface movie S9 AOT (1%) spray impact on tilted superhydrophobic surface REFERENCES AND NOTES V Bergeron, D Bonn, J Y Martin, L Vovelle, Controlling droplet deposition with polymer additives Nature 405, 772–775 (2000) P Galliker, J Schneider, H Eghlidi, S Kress, V Sandoghdar, D Poulikakos, Direct printing of nanostructures by electrostatic autofocussing of ink nanodroplets Nat Commun 3, 890 (2012) J de Ruiter, R Lagraauw, D van den Ende, F Mugele, Wettability-independent bouncing on flat surfaces mediated by thin air films Nat Phys 11, 48–53 (2014) H H Boukhalfa, M Massinon, M Belhamra, F Lebeau, Contribution of spray droplet pinning fragmentation to canopy retention Crop Prot 56, 91–97 (2014) Y H Liu, L Moevius, X Xu, T Qian, J M 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for Fundamental Key Projects (grant 2014CB93220), the National Natural Science Foundation of China (NSFC) (grants 21121001 and 91127025), and the Key Research Program of the Chinese Academy of Sciences (grant KJZD-EW-M01) This work was also supported by NSFC (grants 51473172, 51473173, 51173190, and 21121001) and the “Strategic Priority Research Program” of the Chinese Academy of Sciences (grant XDA09020000) M.S was funded by the Fundamental Key Projects, 2014CB93220, in 2014 Author contributions: L.J and Y.W conceived and designed the experiments M.S and Z.D performed the experiments Z.D fabricated artificial superhydrophobic surfaces M.S., Y.W., and Z.D analyzed the data M.S and Z.D wrote the original manuscript, and L.J., Z.D., and Y.W revised it All authors discussed the results and commented on the manuscript Competing interests: The authors declare that they have no competing interests Data and materials availability: All data needed to evaluate the conclusions in the paper are 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and molecular weight on the rebounding behaviors of polymer solution droplet impacting on hydrophobic surfaces Microfluid Nanofluid 18, 1221–1232 (2014) 24 C Duez, C Ybert, C Clanet, L Bocquet, Making a splash with water repellency Nat Phys 3, 180–183 (2007) Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant Meirong Song, Jie Ju, Siqi Luo, Yuchun Han, Zhichao Dong, Yilin Wang, Zhen Gu, Lingjuan Zhang, Ruiran Hao and Lei Jiang (March 1, 2017) Sci Adv 2017, 3: doi: 10.1126/sciadv.1602188 This article is publisher under a Creative Commons license The specific license under which this article is published is noted on the first page For articles published under CC BY-NC licenses, you may distribute, adapt, or reuse the article for non-commerical purposes Commercial use requires prior permission from the American Association for the Advancement of Science (AAAS) You may request permission by clicking here The following resources related to this article are available online at http://advances.sciencemag.org (This information is current as of March 2, 2017): Updated information and services, including high-resolution figures, can be found in the online version of this article at: http://advances.sciencemag.org/content/3/3/e1602188.full Supporting Online Material can be found at: http://advances.sciencemag.org/content/suppl/2017/02/28/3.3.e1602188.DC1 This article cites 30 articles, of which you can access for free at: http://advances.sciencemag.org/content/3/3/e1602188#BIBL Science Advances (ISSN 2375-2548) publishes new articles weekly The journal is published by the American Association for the Advancement of Science (AAAS), 1200 New York Avenue NW, Washington, DC 20005 Copyright is held by the Authors unless stated otherwise AAAS is the exclusive licensee The title Science Advances is a registered trademark of AAAS Downloaded from http://advances.sciencemag.org/ on March 2, 2017 For articles published under CC BY licenses, you may freely distribute, adapt, or reuse the article, including for commercial purposes, provided you give proper attribution  ... http://advances.sciencemag.org/content/3/3/e1602188#BIBL Science Advances (ISSN 2375-2548) publishes new articles weekly The journal is published by the American Association for the Advancement of Science (AAAS) ,... the Authors unless stated otherwise AAAS is the exclusive licensee The title Science Advances is a registered trademark of AAAS Downloaded from http://advances.sciencemag.org/ on March 2, 2017 For... for the Advancement of Science (AAAS) You may request permission by clicking here The following resources related to this article are available online at http://advances.sciencemag.org (This information