Underwater Transparent Miniature âMechanical Handâ Based on

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Underwater transparent miniature “mechanical hand” based on femtosecond laser-induced controllable oiladhesive patterned glass for oil droplet manipulation Jinglan Huo, Qing Yang, Feng Chen, Jiale Yong, Yao Fang, Jingzhou Zhang, Lin Liu, and Xun Hou Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b00393 • Publication Date (Web): 19 Mar 2017 Downloaded from http://pubs.acs.org on March 22, 2017

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Underwater transparent miniature “mechanical hand” based on femtosecond laser-induced controllable oil-adhesive patterned glass for oil droplet manipulation Jinglan Huo1, Qing Yang2 , Feng Chen1,*, Jiale Yong1,2,*, Yao Fang1, Jingzhou Zhang1 , Lin Liu3， and Xun Hou1 1

State Key Laboratory for Manufacturing System Engineering and Key Laboratory of Photonics Technology for Information of Shaanxi Province, School of Electronics & Information Engineering, Xi’an Jiaotong University, Xi’an, 710049, PR China 2 School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an, 710049, PR China 3 Department of Biological Science and Bioengineering, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi’an Jiaotong University, Xi’an, 710049, PR China

*Corresponding author: [email protected] (F. Chen) [email protected] (J. Yong)

Abstract The development of underwater superoleophobic surfaces makes researchers be swept up in boundless imagination of their applications, thereinto the oil manipulation based on such surface attracts much attention. Here, we show a simple and effective way to fabricate an underwater transparent miniature “mechanical hand” based on controllable oil-adhesive patterned glass prepared by femtosecond laser. The underwater oil-adhesive force of the patterned glasses that compose the “mechanical hand” device could be controlled from ultralow to ultrahigh through adjusting the different fraction of the untreated flat glass area to the laser-ablated rough area. These surfaces also showed a favourable transparency in water. Various oils, such as chloroform, hexadecane, n-dodecane, decane, liquid paraffin and petroleum ether were put to test and confirmed to be repelled by the as-prepared surfaces in water medium. Moreover, the “mechanical hand” was used to implement oil transportation, fusion and rapid capture, which can be applied in the construction of microfluidic devices, in-situ detector and bioreactors. Keywords: underwater superoleophobicity, oil-adhesion, femtosecond laser

“mechanical

hand”,

controllable

1. Introduction Over billions of years of evolution, creatures in the natural world have evolved various unique multifunctional bio-interfaces to adapt the hostile environment.1-6 Thereinto, fish scales with the property of resisting oil pollution in water exert a tremendous fascination on researchers and set off the research tidal wave of underwater superoleophobic surfaces with the oil contact angle (OCA) higher than

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150°.7-14 Jiang et al. first reported an underwater superoleophobic interface on Si substrates based on the oil/water/solid three-phase system inspired by the anti-oil behavior of fish scales.15 They revealed the knowledge that underwater superoleophobicity of fish scales is ascribed to both hydrophilic chemical constitution like proteins and hierarchical rough structures on those surfaces. The underwater superoleophobic surface has many promising and practical applications, such as self-cleaning surfaces,16-18 oil/water separation,19-27 tissue engineering,28-30 microfluidic chips31-32 and micro-oil-droplet manipulation.33-37 One of these highlighted applications of underwater superoleophobic surfaces, of course, is the micro-oil-droplet manipulation, in which case that oil microdroplet can be handled directly and precisely without any loss compared to traditional micro-oil-droplets manipulation technologies such as micropump, microvalve, and microchannel. Those devices have the disadvantages of operation complex and causing the oil loss during the manipulation.38-40 Two kinds of approaches appear at present in order to manipulate the oil microdroplet in water based on the underwater superoleophobic surfaces, that is, in-situ transfer of oil droplet by altering ambient conditions in or around liquid surroundings41-43 and oil droplet transportation by controllable oil-adhesion superoleophobic surfaces.44-52 For the former, Yong et al. reported a method to in-situ transfer oil droplets in water based on femtosecond laser-induced underwater superoleophobic surfaces and switching the density of the water solution.41 An oil droplet could be picked up by simply adding sugar to water environment and be put down by adding water to dilute the sugar water with the reason of changing the buoyancy of it in water. However, the method is lack of stability and practicability for the reason that oil microdroplet easily rolls away when the underwater superoleophobic substrate just gently shakes. Another way of achieving the oil droplet transfer is based on the underwater superoleophobic surfaces with tunable oil-adhesion ranging from ultralow (an oil droplet can roll down when the surface is tilted slightly) to ultrahigh (an oil droplet can be pinned on the surface whether the surface is upright or turned over). Generally, the ultrahigh adhesive surface is used as a “mechanical hand” to pick up an oil droplet from the ultralow adhesive surface to flat surface with no volume loss. The underwater oil droplet adhesion is governed by both the surface chemical composition of materials and the surface roughness, and efforts have been made to develop the methods of fabricating the oil-adhesion controllable surfaces on various materials during recent years. Cheng et al. used self-assembled monolayer technique to modify n-alkanoic acids with different chain lengths on the nanostructured copper films to prepare a series of underwater superoleophobic copper surfaces with controlled oil droplet adhesion which could be used to transport underwater oil droplet without volume loss.48 Zhang et al. fabricated the underwater superoleophobic Ni/NiO surfaces with controllable morphologies on the stainless steel by electro-deposition.49 By being annealed at different heating temperature, the Ni/NiO surfaces with different microstructures were then obtained, which showed underwater superoleophobicity with structure-dependent oil-adhesion. The very high oil-adhesive surface could be regarded as a “mechanical hand” as well.


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By comparison, oil microdroplet manipulation based on controllable adhesion surfaces owns higher stability. However, the above-mentioned methods for preparing controllable oil-adhesive surfaces need elevated temperature and complex preparation procedures. What’s more, those underwater superoleophobic surfaces are usually adiaphanous, which may limit their application in underwater image formation and monitor operation process accurately. All these defects require building a kind of transparent underwater adjustable oil-adhesive surface via a simple and effective way. Here, we demonstrate a simple way of realizing underwater transparent superoleophobic patterned glass surfaces with tunable oil-adhesion by femtosecond laser. The surfaces consist of laser-induced hierarchical micro/nano rough structure and untreated flat glass. Wherein, the middle unstructured flat glass surface domain is round and surrounded by structured rough surface domain. The fabricated surfaces show superoleophobicity in the water, and their oil-adhesion can be adjusted flexibly by changing the fraction of the untreated flat glass region to the laser-ablated rough region. Furthermore, the property endows the as-prepared surfaces with many practical applications for a miniature “mechanical hand” in the no loss transportation, fusion and capture of oil microdroplet. Importantly, the as-prepared superoleophobic glass surface is proved to have a favourable transparency.

2. Experimental Section 2.1 Surface laser ablation A regenerative amplified Ti: sapphire laser system (Coherent Libra-usp-he) that produces the femtosecond laser (pulse duration = 50fs; central wavelength = 800nm; frequency = 1 kHz) was employed to ablating sample surfaces. The laser energy was modulated by an attenuator, and laser beam was focused through a microscope objective lens (20×, NA = 0.45, Nikon) on the glass slide (SAIL BRAND) surface which was mounted on a motorized precise x-y-z translation stage controlled by a computer. Through designing the specific assembly programs, the surface configuration composing of micro/nano structures at the diverse scales was processed in one step. 2.2 Structured center circle array Figure 1 shows the schematic illustration of fabricating the center circle array fabricated by line-by-line scanning femtosecond laser on a glass slide. The gray domain demonstrates the structured area, on which the red and yellow lines with the arrows indicate the scanning route of the focused laser beam. The speed of laser scanning was set at 2 mm/s under a constant average laser power of 15 mW, meanwhile, the interval between adjacent horizontal parallel lines was held unchanging at 2 µm. After the femtosecond laser irradiation, the unstructured flat area came into being a circle shape (the blue domain in Figure 1) surrounded by laser-induced rough structures. Each machining unit including a center circle and surrounding structures with square edge has two crucial parameters, that is the side length (SL) of a square and the diameter (D) of the center circle. In order to control variables, the value of the SL was set to fixed number of 200 µm. The flat center circle


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size was controlled by adjusting its D through the program in computer.

Fig. 1 Schematic illustration of fabricating the center circle glass pattern.

2.3 Morphology analysis and sample characterization The morphology of the laser-ablated pattern surfaces was observed by a Quanta FEG 250 scanning electron microscope (SEM, FEI, America). The transmission spectra with the wavelength ranging from 300 nm to 900 nm was measured using a UV 3010 spectrophotometer (Hitachi, Japan). The 1,2-dichloroethane was chosen as the main tested oil in the experiment. The contact and sliding angles, as well as the manipulation of oil droplets were measured or observed by a JC2000D Contact-angle System (Powereach, China) and a charge-coupled device (CCD) camera system.

3. Results and Discussion Figure 2a shows the SEM image of the entire laser-scanned glass surface (D = 0 µm). After the laser irradiation, periodical hierarchical rough micro-islands with the size of about 10µm were formed on the sample surface due to the overlap among the laser pulses ablated craters. Further magnified SEM image shows that each micro-island surface presents a loose and porous structure and is covered by hundreds of accumulational or sporadic nano-grains forming from the ablation of laser pulses and the recrystallization of ejected particles (Figure 2b). When a water droplet was in touch with the as-prepared sample surface, it spread out in a single second with the water contact angle (WCA) of only 15° (Figure 2d), which was small enough in comparison with the WCA of 78° on a flat glass surface without any laser treating (Figure 2c), demonstrating the quasi-superhydrophilicity of the femtosecond laser entirely scanned surface. Generally, superhydrophilic substrate in air becomes superoleophobic in water. Once immersed into water, the OCA of a 1,2-dichloroethane oil droplet on the micro/nano rough surface augmented from 100° for an untreated flat one to 160±1°, indicating the transition of the surface from underwater ordinary oleophobicity to superoleophobicity (Figure 2e,f). At the same time, the ultralow oil-adhesion in water was also achieved that an oil droplet could roll off easily even the structured surface was tilted only 1° (Figure 2g).


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Fig. 2 (a) SEM image of the structure irradiated line-by-line by femtosecond laser and (b) high magnification SEM image of a single micro-island decorating with nano-grains. (c,d) Shapes of a water droplet on the (c) flat surface and (d) rough surface in air, respectively. (e,f) Shapes of a 1,2-dichloroethane droplet on the (e) flat surface and (f) rough surface in water, respectively. (g) Time sequence of snapshots of a 1,2-dichloroethane droplet rolling on the surface tilted 1°.

Flat glass slide surface showed oleophobicity in water, while the femtosecond laser-induced rough microstructures could magnify the surface wettability to underwater superoleophobicity because of the formation of underwater Cassie contact state.50 Water wetted the rough surface and was captured into the microstructures as soon as the sample was immersed in water, forming an oil-repellent trapped water layer. When an oil droplet was placed onto the sample surface in water, the droplet indeed sat on a solid-water composite interface and only touched the top of the nano-grains. The OCA of an underwater oil droplet on such interface, θ * , can be described as follows: cos θ * = f cos θ + f − 1 where, f is the area fraction of the rough solid surface which is contact with the oil droplet, θ is the OCA of an underwater oil droplet on the untreated flat glass surface. The measured θ and θ * are 100° and 160°, respectively, so we can calculated f and its value equals 7.3%, verifying so small contact area between underwater oil droplet and femtosecond laser ablated substrate. Furthermore, other oils having different surface tensions were tested on the as-prepared sample with ultralow adhesion. The sample surface showed underwater superoleophobicity and ultralow oil-adhesion to all those oils, including chloroform, hexadecane, n-dodecane, decane, liquid paraffin and petroleum ether, as shown in Figure 3. Those oil droplets could easily roll down when the surface was in a small


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angle, and their oil sliding angles (OSAs) were all less than 2°.

Fig. 3 Femtosecond laser-ablated surface (D = 0 µm) showing underwater superoleophobicity and ultralow oil-adhesion for various oils.

By changing the value of the parameter D, the topographies of the sample surfaces also change correspondingly. As shown in the SEM images of laser-irradiated periodic center circle arrays (Figure 4), the sample surfaces are composing of unprocessed flat circle and processed rough structures around. The D of the center circle is regarded as the paramount parameter having an effect not only on the patterning structures but also on the oil wettability and adhesion of the as-prepared surface. With the increase of D, the center circle area increases, that is, on the premise of making the value of L constant, the flat-to-rough fraction ratio increases as well (Figure 4a-d). Figure 4e,f indicate the enlarged views of laser-induced hierarchical rough micro-islands structures in the heterogeneous patterning systemation. That is the same as the entirely scanned rough structures (D = 0 µm) with which the surface shows underwater superoleophobicity and ultralow oil-adhesion.


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Fig. 4 SEM images of the as-prepared center circle array patterns with the diameters (Ds) of (a) 40 µm, (b) 80 µm, (c) 160 µm and (d) 200 µm. Insets in (a) and (d) show the dynamic behaviors of a 7µL oil droplet rolling easily and pinning on the overturned surface. (e,f) Larger magnification SEM images of the micro/nano structures on the femtosecond laser treated region.

Figure 5 illustrates the relation between D and the static OCA and dynamic oil sliding angle (OSA) on the as-prepared surfaces. It could be found obviously that all of the samples present underwater superoleophobicity with the OCAs being about 160° and the oil droplet looking like the torispherical shapes. Taking the two representative pattern surfaces for examples, the OCA of the surface with D = 0 µm reaches up to 160±1°, and that of the one with D = 200 µm is still as high as 158±2°. By contrast, the OSAs that enable to characterize the surface adhesion are quite different as adjusting the value of D. When D ranges from 0 µm to 40 µm , the oil droplet can roll down easily when the surface is inclined a small angle below 2° or even get a bit of shake (insets in Figure 4a and Figure 5), manifesting the ultralow adhesion the surface to oil as shown in area Ⅰ in Figure 5. In the case of the value of D increasing from 40 µm to 180 µm, the OSAs curve increases sharply as shown in area Ⅱ in Figure 5. The inset in area Ⅱ indicates the moment of oil droplet starting rolling with the OSA of 48±2° on the surface with D = 120 µm. The oil droplet, however dramatic, can be pinned on the surfaces (D = 180 µm and 200 µm) even when the surfaces are upright or up side down (insets in Figure 4d and Figure 5), revealing an ultrahigh oil-adhesion with OSAs being expressed via 180° in area Ⅲ in Figure 5. It is obvious from the curve that the oil-adhesion of the processed periodical center circle pattern sample is controllable with the value of D modulating from 40 µm to 180 µm, which is ascribe to the proportion of laser-induced micro/nano structures region to unstructured region in the patterned substrates. In addition, the volume of oil droplet also has an impact on the OSA of an oil microdroplet on the as-prepared surface. Generally, the larger size of the oil droplet, the smaller the OSA.51 Taking the patterned surface with D of 80 µm for a proper example, with the volume of the oil droplet increasing from 7 µL to 15 µL, and then to 20 µL, the OSA decreases from 11±2° to 7±1°, and then to 2±1°. It is found that with the increase of the volume of the oil droplet, the underwater OSA reduces accordingly.


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Fig. 5 Relationships between the D of the unstructured center circle and the OCA (left)/OSA (right).

The mechanism of tunable surface adhesion is discussed below. As is known to all, the liquid adhesion of a surface is governed by both the surface chemical composition and the surface morphologic structure.46,53 Since the chemical composition of the glass surfaces have little change after the laser ablation, the latter factor is the foremost point to control the adhesion.54 In this work, laser-induced periodical surface center circle array pattern consists of unstructured flat domain and structured rough domain. As for the former, the intrinsic hydrophilicity of the glass sheet results in its intrinsic ordinary underwater oleophobicity, giving rise to a large contact area between oil droplet and the surface. This contact state can be regarded as the Young state (Figure 6c), in which oil droplet fully wets the non-ablated flat surface.50,55 The Young contact state not only facilitates the formation of successive three-phase contact line (TCL) at the solid/oil/water interface, but also expands the van der Waals force between the oil/solid molecules, resulting in an ultrahigh adhesion with oil droplet being adhered to the surface. With regard to the latter rough domain, the contact between the underwater oil and such rough domain is at Cassie contact state (Figure 6c). The oil droplet only contacts with the tip of the rough microstructure and results in an inconsecutive TCL. The small contact area and the inconsecutive TCL rendered by irregular distribution of nano-grains diminish the van der Waals force. Therefore, such laser-induced rough domain generates very small adhesion to the oil droplet. As is shown in the schematic diagram (Figure 6), by controlling the area fraction of the structured rough domain and unstructured flat domain, the oil droplet adhesion can be adjusted from ultralow to ultrahigh.


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Fig. 6 The schematic illustration of the contact model of underwater oil droplet on a heterogeneous topographic glass surface including both hierarchical rough structures and flat domain: (a) 45° tilted view, (b) top view, and (c) section view.

The samples with tunable underwater oil-adhesion can be used as a “mechanical hand” to manipulate oil droplet in the water environment. Figure 7a shows the process of “no loss oil transition” from an ultralow adhesive surface to an ultrahigh one. The medial adhesion surface (M-Surface in the Figure 7a) with the D of 160 µm and OSA of 65° is served as a “mechanical hand”, which can be moved up and down to pick up a 7 µL oil droplet from the ultralow adhesive surface (L-Surface in the Figure 7a) with D of 0 µm (OSA = 2°) and release it onto an ultrahigh adhesive surface (H-Surface in the Figure 7a) with D of 200 µm (OSA = 180°) without any loss. In the similar way, oil droplets fusion can be achieved using the equipment whose parameters are the same as those mentioned above, as shown in Figure 7b. A 7 µL oil microdroplet is placed on the L-Surface and H-Surface respectively in advance. Then the oil microdroplet on the L-Surface is taken up by the M-Surface that is surved as the “mechanical hand”, and fuses with another one on the H-Surface losslessly and then pins on the surface rather than rolls away. This elaborate device reveals the potential applications of the controlled adhesion surfaces such as bio-detection, in-situ microreactor and cell engineering.


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Fig. 7 (a) Process of transferring oil droplet in water using the medial oil-adhesive surface (M-Surface) as a “mechanical hand”. M-Surface, ultralow oil-adhesive surface (L-Surface) and ultrahigh oil-adhesive surface (H-Surface) are laser-ablated patterned glass surfaces with the D of 160µm, 0µm and 200µm, respectively. The red and blue arrows show the moving direction of “mechanical hand” and operation step sequence, respectively. (b) Process of the fusion of two 7 µL 1,2-dichloroethane droplets. The blue arrows show the operation step sequence.

Through piecing together the two extreme adhesion surfaces to a larger one achieved easily by femtosecond laser processing, the shift oil-capture is realized on that, as shown in Figure 8. The larger surface consists of two adjacent ultralow and ultrahigh adhesive surfaces, whose Ds are 0 µm and 200 µm, respectively. When the oil droplet was put on the region of the ultralow adhesive surface that was tilted up just 3°, the oil droplet rolled down freely without any residues until it touched the border between the two pattern surfaces (Figure 8a-d). On account of the impact of the adhesive force, the oil droplet that just crossed the middle border “braked” suddenly, and vibrated back and forth for several times (Figure 8e-g). During the process, the kinetic energy of the rushing oil droplet transformed into internal energy, and then consumed away due to swing in-situ. Finally, the oil droplet pinned on the surface, which realized the no-loss oil capture on specific location (Figure 8h).


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Fig. 8 Process of swiftly capturing of a 7 µL oil droplet by ultrahigh adhesive surface (right domain) once rolling down from ultralow adhesive surface (left domain).

In addition, the good optical transparency of the femtosecond laser structured slide glass in the water environment is verified by the visible spectra, as shown in Figure 9. During the measurement, the transmittance of flat glass surface in water is regarded as a reference quality with value of 100%. At visible wavelengths, the transmittance of the laser-ablated patterned glass surface with various Ds nearly overtops 80% except for the entire processing rough surface with the ultralow oil-adhesion whose transmittance in the visible spectra is between 75% and 90%. The insets in Figure 9 show the transparency images of entire laser-ablated surface with D of 0 in air and in water. It can be seen that the letters beneath the as-prepared rough surface are misty in air. However, after dropping a drop of water on and covering all the rough region, the letters “xjtu” become clear, which reflects that the sample in water owns a higher transparency compared to that in air. It is because that the refractive index of glass is close to that of water. Once immersing into water, the interface of micro/nano structures is filled with water on account of its superhydrophilicity, which effectively reduces the refraction and scattering of light when passing through the as-prepared sample. With the increase of D, the structured rough domain decreases, and the scattering and refraction of the light beams passing through the interface between the glass surface and water reduce accordingly, which gives rise to the enhancement of the transmittance. When the D is equal or greater than 80 µm, the transmittance curve tends to stabilize and practically approaches to that of the flat glass surface. The favourable light-admitting quality endows the laser-induced glass samples with more potential applications in the underwater optics and biological observation field.

Fig. 9 Transmittance of flat glass surface and as-prepared patterned surfaces with different Ds (0 µm, 40 µm, 80 µm, 120 µm, 160 µm, 200 µm) in water medium. The insets are images of the entire laser-ablated rough surfaces putting in air and in water, respectively.

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In conclusion, a simple and facile method was proposed to fabricate underwater transparent miniature “mechanical hand” based on superoleophobic patterned glass surfaces with controllable oil-adhesion ranging from ultralow to ultrahigh. The surfaces consist of periodically arranged structured micro/nano dual-scale rough domain with superoleophobicity and non-structured flat center circle domain with oleophobicity. By varying the area ratio of the two, that is, diameter of the center circle specifically, the surface morphologies and related adhesions could be tuned. The “mechanical hand” based on the patterned surfaces with this unique adhesive property was successfully applied in oil transportation, fusion and rapid capture. What’s more, the as-prepared glass “mechanical hand” exhibited a favourable transparency. In addition, the underwater superoleophobicity was verified by various oils with different surface tension and density. The controlling of the oil-adhesion on the underwater superoleophobic glass surface by changing the fraction of different wettability area has many potential applications in all sorts of fields, such as antifouling, droplet microreaction, microfluidic devices, and bioengineering.

Author Contributions F.C. directed and supervised the research. J.Y. proposed main research idea and designed this experiment project. J.H. and L.L. performed the experiment and wrote the manuscript. Other authors contributed significant discussions and revised the paper.

Acknowledgements This work is supported by the National Science Foundation of China under the Grant nos. 51335008 and 61475124, the NSAF Grant No. U1630111, the Special-funded programme on national key scientific instruments and equipment development of China under the Grant no.2012YQ12004706, China Postdoctoral Science Foundation under the Grant no. 2016M600786, the Collaborative Innovation Center of Suzhou Nano Science and Technology and the International Joint Research Center for Micro/Nano Manufacturing and Measurement Technologies. The SEM work was done at International Center for Dielectric Research (ICDR), Xi’an Jiaotong University.

References (1) Koch, K.; Bhushan, B.; Barthlott, W. Multifunctional Surface Structures of Plants: An Inspiration for Biomimetics. Prog. Mater. Sci. 2009, 54, 137-178. (2) Darmanin, T.; Guittard, F. Superhydrophobic and Superoleophobic Properties in Nature. Mater.


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Today 2015, 18, 273-285. (3) Vassilia, Z.; Emmanuel, S.; Marios, B.; Emmanuel, S.; Panagiotis, T.; Spiros, H. A.; Costas, F. Biomimetic Artificial Surfaces Quantitatively Reproduce the Water Repellency of a Lotus Leaf. Adv. Mater. 2008, 20, 4049-4054. (4) Feng, L.; Zhang, Y. N.; Xi, J. M.; Zhu, Y.; Wang, N.; Xia, F.; Jiang, L. Petal Effect: A Superhydrophobic State with High Adhesive Force. Langmuir 2008, 24, 4114-4119. (5) Zheng, Y. M.; Gao, X. F.; Jiang, L. Directional Adhesion of Superhydrophobic Butterfly Wings. Soft Matter 2007, 3, 178-182. (6) Feng, L.; Li, S. H.; Li, Y. S.; Li, H. J.; Zhang, L. J.; Zhai, J.; Song, Y. L.; Liu, B. Q.; Jiang, L.; Zhu, D. B. Super-Hydrophobic Surface: From Nature to Artificial. Adv. Mater. 2002, 14, 1857-1860. (7) Li, K.; Ju, J.; Xue, Z. X.; Ma, J.; Feng, L.; Gao, S.; Jiang, L. Structured Cone Arrays for Continuous and Effective Collection of Micron-Sized Oil Droplets from Water. Nat. Commun. 2013, 4, 2276. (8) Jin, M.; Li, S. S.; Wang, J.; Xue, Z. X.; Liao, M. Y.; Wang, S. T. Underwater Superoleophilicity to Superoleophobicity: Role of Trapped Air. Chem. Commun. 2012, 48, 11745-11747. (9) Cheng, Q. F.; Li, M. Z.; Zheng, Y. M.; Su, B.; Wang, S. T.; Jiang, L. Janus Interface Materials: Superhydrophobic Air/Solid Interface and Superoleophobic Water/Solid Interface Inspired by a Lotus Leaf. Soft Matter 2011, 7, 5948-5951. (10) Liu, X. L.; Zhou, J.; Xue, Z. X.; Gao, J.; Meng, J. X.; Wang, S. T.; Jiang, L. Clam’s Shell Inspired High-Energy Inorganic Coating with Underwater Low Adhesive Superoleophobicity. Adv. Mater. 2012, 24, 3401-3405. (11) Cai, Y.; Lin, L.; Xue, Z. X.; Liu, M. J.; Wang, S. T.; Jiang, L. Filefish-Inspired Surface Design for Anisotropic Underwater Oleophobicity. Adv. Funct. Mater. 2014, 24, 809-816. (12) Brown, P. S.; Bhushan, B. Durable Superoleophobic Polypropylene Surfaces. Phil. Trans. R. Soc. A 2016, 374, 20160193. (13) Liu, W. D.; Liu, X. Y.; Xiang, S. Y.; Chen, Y. X.; Fang, L. P.; Yang, B. Functional Interface Based on Silicon Artificial Chamfer Nanocylinder Arrays (CNCAs) with Underwater Superoleophobicity and Anisotropic Properties. Nano Res. 2016, 9, 3141-3151. (14) Yong, J. L.; Chen, F.; Yang, Q.; Zhang, D. S.; Farooq, U.; Du, G. Q.; Hou, X. Bioinspired Underwater Superoleophobic Surface with Ultralow Oil-Adhesion Achieved by Femtosecond Laser Microfabrication. J. Mater. Chem. A 2014, 2, 8790-8795. (15) Liu, M. J.; Wang, S. T.; Wei, Z. X.; Song, Y. L.; Jiang, L. Bioinspired Design of a Superoleophobic and Low Adhesive Water/Solid Interface. Adv. Mater. 2009, 21, 665-669. (16) Gao, S. J.; Sun, J. C.; Liu, P. P.; Zhang, F.; Zhang, W. B.; Yuan, S. L.; Li, J. Y.; Jin, J. A Robust Polyionized Hydrogel with an Unprecedented Underwater Anti-Crude-Oil-Adhesion Property. Adv. Mater. 2016, 28, 5307-5314. (17) Wang, Z. W.; Zhu, L. Q.; Li, W. P.; Liu, H. C. Bioinspired in Situ Growth of Conversion Films with Underwater Superoleophobicity and Excellent Self-Cleaning Performance. ACS Appl. Mater. Interfaces 2013, 5, 10904-10911. (18) Yin, K.; Song, Y. X.; Dong, X. R.; Wang, C.; Duan, J. A. Underwater Superoleophobicity, Anti-Oil and Ultra-Broadband Enhanced Absorption of Metallic Surfaces Produced by a Femtosecond Laser Inspired by Fish and Chameleons. Sci. Rep. 2016, 6, 36557. (19) Xue, Z. X.; Cao, Y. Z.; Liu, N.; Feng, L.; Jiang, L. Special Wettable Materials for Oil/Water


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Separation. J. Mater. Chem. A 2014, 2, 2445-2460. (20) Zhu, Y. Z.; Zhang, F.; Wang, D.; Pei, X. F.; Zhang, W. B.; Jin, J. A Novel Zwitterionic Polyelectrolyte Grafted PVDF Membrane for Thoroughly Separating Oil from Water with Ultrahigh Efficiency. J. Mater. Chem. A 2013, 1, 5758-5765. (21) Zhou, C. L.; Cheng, J.; Hou, K.; Zhao, A.; Pi, P. H.; Wen, X. F.; Xu, S. P. Superhydrophilic and Underwater Superoleophobic Titania Nanowires Surface for Oil Repellency and Oil/Water Separation. Chem. Eng. J. 2016, 301, 249-256. (22) Zhang, F.; Gao, S. J.; Zhu, Y. Z.; Jin, J. Alkaline-Induced Superhydrophilic/Underwater Superoleophobic Polyacrylonitrile Membranes with Ultralow Oil-Adhesion for High-Efficient Oil/Water Separation. J. Membr. Sci. 2016, 513, 67-73. (23) Luo, Z. Y.; Chen, K. X.; Wang, Y. Q.; Wang, J. H.; Mo, D. C.; Lyu, S. S. Superhydrophilic Nickel Nanoparticles with Cole-Shell Structure to Decorate Copper Mesh for Efficient Oil/Water Separation. J. Phys. Chem. C 2016, 120, 12685-12692. (24) Teng, C.; Xie, D.; Wang, J. F.; Zhu, Y.; Jiang, L. A Strong, Underwater Superoleophobic PNIPAM-Clay Nanocomposite Hydrogel. J. Mater. Chem. A 2016, 4, 12884-12888. (25) Ge, J. L.; Zhang, J. C.; Wang, F.; Li, Zhao. L.; Yu, J. Y.; Ding, B. Superhydrophilic and Underwater Superoleophobic Nanofibrous Membrane with Hierarchical Structured Skin for Effective Oil-In-Water Emulsion Separation. J. Mater. Chem. A 2017, 5, 497-502. (26) Yong, J. L.; Chen, F.; Yang, Q.; Bian, H.; Du, G. Q.; Shan, C.; Huo, J. L.; Fang, Y.; Hou, X. Oil-Water Separation: A Gift from the Desert. Adv. Mater. Interfaces 2016, 3, 1500650. (27) Liu, Y. Q.; Zhang, Y. L.; Fu, X. Y.; Sun, H. B. Bioinspired Underwater Superoleophobic Membrane Based on a Graphene Oxide Coated Wire Mesh for Efficient Oil/Water Separation. ACS Appl. Mater. Interfaces 2015, 7, 20930-20936. (28) Wang, S. T.; Liu, X. L. Three-Dimensional Nano-biointerface as a New Platform for Guiding Cell Fate. Chem. Soc. Rev. 2014, 43, 2385-2401. (29) Chen, L.; Liu, M. J.; Bai, H.; Chen, P. P.; Xia, F.; Han, D.; Jiang, L. Antiplatelet and Thermally Responsive Poly(N-Isopropylamide) Surface with Nanoscale Topography. J. Am. Chem. Soc. 2009, 131, 10467-10472. (30) Liu, W. D.; Liu, X. Y.; Fangteng, J. Z.; Wang, S. L.; Fang, L. P.; Shen, H. Z.; Xiang, S. Y.; Sun, H. C.; Yang, B. Bioinspired Polyethylene Terephthalate Nanocone Array with Underwater Superoleophobicity and Anti-Bioadhesion Properties. Nanoscale 2014, 6, 13845-13853. (31) Wu, D.; Wu, S. Z.; Chen, Q. D.; Zhao, S.; Zhang, H.; Jiao, J.; Piersol, J. A.; Wang, J. N.; Sun, H. B.; Jiang, L. Facile Creation of Hierarchical PDMS Microstructures with Extreme Underwater Superoleophobicity for Anti-Oil Application in Microfluidic Channels. Lab Chip 2011, 11, 3873-3879. (32) Xu, B. B.; Zhang, Y. L.; Xia, H.; Dong, W. F.; Ding, H.; Sun, H. B. Lab Chip 2013, 13, 1677-1690. (33) Su, B.; Wang, S. T.; Song, Y. L.; Jiang, L. Utilizing Superhydrophilic Materials to Manipulate Oil Droplets Arbitrarily in Water. Soft Matter 2011, 7, 5144-5149. (34) Yao, X.; Gao, J.; Song, Y. L.; Jiang, L. Superoleophobic Surface with Controllable Oil Adhesion and Their Application in Oil Transportation. Adv. Funct. Mater. 2011, 21, 4270-4276. (35) Huang, S.; Song, J. L.; Lu, Y.; Chen, F. Z.; Zheng, H. X.; Yang, X. L.; Liu, X.; Sun, J.; Carmalt, C. J.; Parkin, I. P.; Xu, W. J. Underwater Spontaneous Pumpless Transportation of Nonpolar Organic Liquids on Extreme Wettability Patterns. ACS Appl. Mater. Interfaces 2016, 8,


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ToC figure:


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Fig. 1 Schematic illustration of fabricating the center circle glass pattern. 18x6mm (300 x 300 DPI)


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Fig. 2 (a) SEM image of the structure irradiated line-by-line by femtosecond laser and (b) high magnification SEM image of a single micro-island decorating with nano-grains. (c,d) Shapes of a water droplet on the (c) flat surface and (d) rough surface in air, respectively. (e,f) Shapes of a 1,2-dichloroethane droplet on the (e) flat surface and (f) rough surface in water, respectively. (g) Time sequence of snapshots of a 1,2dichloroethane droplet rolling on the surface tilted 1°. 70x99mm (300 x 300 DPI)


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Fig. 3 Femtosecond laser-ablated surface (D = 0 µm) showing underwater superoleophobicity and ultralow oil-adhesion for various oils. 66x50mm (300 x 300 DPI)


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Fig. 4 SEM images of the as-prepared center circle array patterns with the diameters (Ds) of (a) 40 µm, (b) 80 µm, (c) 160 µm and (d) 200 µm. Insets in (a) and (d) show the dynamic behaviors of a 7µL oil droplet rolling easily and pinning on the overturned surface. (e,f) Larger magnification SEM images of the micro/nano structures on the femtosecond laser treated region. 59x35mm (300 x 300 DPI)


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Fig. 5 Relationships between the D of the unstructured center circle and the OCA (left)/OSA (right). 68x46mm (300 x 300 DPI)


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The schematic illustration of the contact model of underwater oil droplet on a heterogeneous topographic glass surface including both hierarchical rough structures and flat domain: (a) 45° tilted view, (b) top view, and (c) section view. 50x46mm (300 x 300 DPI)


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Fig. 7 (a) Process of transferring oil droplet in water using the medial oil-adhesive surface (M-Surface) as a “mechanical hand”. M-Surface, ultralow oil-adhesive surface (L-Surface) and ultrahigh oil-adhesive surface (H-Surface) are laser-ablated patterned glass surfaces with the D of 160µm, 0µm and 200µm, respectively. The red and blue arrows show the moving direction of “mechanical hand” and operation step sequence, respectively. (b) Process of the fusion of two 7 µL 1,2-dichloroethane droplets. The blue arrows show the operation step sequence. 554x424mm (72 x 72 DPI)


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Fig. 8 Process of a swiftly capturing 7 µL oil droplet by ultrahigh adhesive surface (right domain) once rolling down from ultralow adhesive surface (left domain). 47x18mm (300 x 300 DPI)


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Fig. 9 Transmittance of flat glass surface and as-prepared patterned surfaces with different Ds (0 µm, 40 µm, 80 µm, 120 µm, 160 µm, 200 µm) in water medium. The insets are different images of the entire laserablated rough surfaces putting in air and in water. 590x449mm (72 x 72 DPI)


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458x416mm (72 x 72 DPI)


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Underwater Transparent Miniature âMechanical Handâ Based on

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