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一般地,用水滴在固体表面的接触角来表征表面的浸润状态。在固-液-气三相相交点处,相切于水滴表面直线与固体表面的夹角即为接触角,如图 1所示,液滴在固-液-气三相表面张力的作用下处于稳定的状态。当固体发生倾斜时,水滴的左右接触角不会相同,此时在斜面下方的称为前进角,在斜面上方的称为后退角。当液滴滚落的一瞬间,前进角减去后退角得到的差值即为滚动角。
在化学成分均一和完全水平的表面,根据Yong’s方程[28],可以得到接触角的计算方程:
$ \cos \theta=\frac{\gamma_{\mathrm{s}, \mathrm{g}}-\gamma_{\mathrm{s,l} }}{\gamma_{ \mathrm{l,g}}} $
(1) 式中, γs, g表示固气间的界面张力, γs, l表示固液间的界面张力, γl, g表示液气间的界面张力。
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Yong’s方程具有一个严苛的前提条件,即表面的完全光滑和清洁。但是现实中的材料很难满足化学成分均一和表面完全平整的条件。当在光滑表面用全氟烷(已知的表面能最低的物质)修饰时,也仅能达到疏水的状态,因此绝对不能忽略表面微结构对疏水性能的影响。考虑到粗糙度对接触角的影响,参考文献[29]中提出了改进的理论模型。
(1) Wenzel模型。当水滴在微结构表面时,可以浸满微结构的凹陷中,如图 2所示。在稳定状态下,Wenzel模型所述的实际接触角θW和Yong’s方程所说的理想接触角θ可以用以下方程表示:
$ \cos \theta_{\mathrm{W}}=\frac{r\left(\gamma_{\mathrm{s}, \mathrm{g}}-\gamma_{\mathrm{s, l}}\right)}{\gamma_{\mathrm{g, l}}}=r \cos \theta $
(2) 式中, r是表面粗糙因子。Wenzel模型的特点为:当表面粗糙因子大于1时,增加r会使得疏水的表面更加疏水;但由于水滴浸满微结构的凹陷,导致表面的粘附性变得非常大。
(2) Cassie模型。水滴与固体的微结构之间存在大量的空气,凹陷内部存在三相接触面,而非水滴直接浸满凹陷,如图 3所示。在此状态下,实际的接触面积应该分为两个部分:水滴和固体的接触;水滴与凹陷中空气的接触。如果水滴与基板的接触面积与总接触面积之比是fs, l,则此时的实际接触角θC可表示为:
$ \cos \theta_{\mathrm{C}}=f_{\mathrm{s, l}} \cos \theta+f_{\mathrm{s, l}}-1 $
(3) Wenzel模型和Cassie模型之间的最大区别在于微观结构中存在空气与否。微结构内是两相接触还是三相接触,会极大地影响疏水性。一般地,处于Wenzel状态的低表面能表面难以达到超疏水的效果,接触角低于150°或者接触角高于150°但滚动角很大具有极强的粘附性。而Cassie状态的表面不具有这种特点,当接触角大于150°时,滚动角将会变得很小,具有超疏水效果。因此,理想状态下应该制备出Cassie状态的表面,可以很好地改善疏水性能。Cassie状态下,尽可能地增大水滴与凹槽内空气的接触面积可以有效地提升疏水性能;但是当水滴与凹槽内空气的接触面积太大时,凹槽内空气不足以支撑液滴,表面张力的平衡被打破,将产生从Cassie状态到Wenzel状态的变化。因此,控制气液、气固接触面的比例就显得尤为重要。激光刻蚀的方式,能通过调节工艺参量,精确地控制表面微结构的形貌,获得高稳定性的超疏水表面。
激光刻蚀法制备仿生超疏水表面的研究进展
Progress in fabrication of biomimetic superhydrophobic surfaces by laser etching
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摘要: 超疏水表面因具有滑移减阻、防腐蚀、防摩擦等良好的性能,获得广泛的关注。激光刻蚀超疏水表面具有可控、简单、稳定、环保等优点,有望实现工业化生产。首先梳理了超疏水表面的理论模型与影响因素,概述了国内外激光刻蚀超疏水表面的方法,讨论了飞秒、皮秒和纳秒激光制备超疏水表面的优缺点, 最后提出了激光刻蚀超疏水表面技术的展望。今后的研究应该坚持以降低生产成本、减少工艺步骤、提高生产效率、绿色节能环保等为基础,着重提高表面微结构的稳定性与持久性。超疏水表面将朝着多功能化与智能化的方向发展。Abstract: Superhydrophobic surfaces have gained wide attention due to their good properties such as slip resistance, corrosion resistance, and anti-friction. Superhydrophobic surfaces etched by laser have advantages of controllability, simplicity, stability, environmental protection, etc. It is expected to achieve industrial production. Firstly, theoretical models and influencing factors of superhydrophobic surfaces are reviewed. Also, the methods of laser etching superhydrophobic surfaces at home and abroad are summarized. The advantages and disadvantages of femtosecond, picosecond and nanosecond lasers for superhydrophobic surfaces are discussed. Finally, the prospect of laser etching superhydrophobic surface technology is put forward. Future research should insist on reducing the production cost, reducing the process steps, improving production efficiency, saving energy and keeping environmental protection, etc. It is important to improve the stability and durability of surface microstructure. Superhydrophobic surfaces will move towards multi-functionality and intelligence.
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Key words:
- laser technique /
- superhydrophobic /
- laser etching /
- laser parameter /
- microstructure
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图 6 不锈钢表面飞秒激光加工与水热法复合制备的双尺度微结构[32]
a—能量密度为2.4J/cm2的飞秒激光制备的样品30°倾斜扫描电子显微镜图 b—激光加工后再用水热法制备的双尺度微结构30°倾斜扫描电子显微镜图 c—双尺度微结构局部放大图 d—水滴在双尺度微结构表面的形貌图
图 7 超疏水表面扫描电子显微镜图[37]
图 8 纳秒激光刻蚀表面扫描电子显微镜图[41]
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[1] LI J Y, LU Sh X, XU W G, et al. Fabrication of stable Ni-AlNi-AlO superhydrophobic surface on aluminum substrate for self-cleaning, anti-corrosive and catalytic performance[J].Journal of Materials Science, 2018, 53(2):1097-1109. doi: 10.1007/s10853-017-1569-5 [2] SHASHANK S, YUNG C S.Superhydrophobic contoured surfaces created on metal and polymer using a femtosecond laser [J].Applied Surface Science, 2017, 405(2):465-475. [3] MORADI S, KAMAI S, ENGLEZOS P, et al.Femtosecond laser irradiation of metallic surfaces:effects of laser parameters on super hydrophobicity [J].Nanotechnology, 2013, 24(41):1-12. [4] LI J, ZHAO Sh C, DU F, et al. Study on superhydrophobic and corrosion resistant surfaces constructed by laser grooves and grid structures[J].Journal of Materials Engineering, 2018, 46(5):86-91(in Ch-inese). [5] LI B J, LI H, HUANG L J, et al. Femtosecond pulsed laser textured titanium surfaces with stable superhydrophilicity and superhydrophobicity [J].Applied Surface Science, 2016, 389(7):585-593. [6] HUANG Ch, YE X, YANG X H, et al. Preparation of a superhydrophobic aluminium alloy surface by UV laser [J].Surface Engineering, 2017, 28(6):1-7. [7] MAURER J A, MILLER M J, BARTOLUCCI S F.Self-cleaning superhydrophobic nanocomposite surfaces generated by laser pulse heating[J].Journal of Colloid and Interface Science, 2018, 524 (6):204-208. [8] XUE L, YU J Y, MA X Sh, et al. Femtosecond laser fabricated wetting copper surfaces and their anti-icing properties [J].Aeronautical Ma-nufacturing Technology, 2018, 61(12):74-79 (in Chinese). [9] FARSHCHIAN B, GATABI J R, BERNICK S M, et al. Scaling and mechanism of droplet array formation on a laser-ablated superhydrophobic grid[J].Colloids and Surfaces, 2018, A547(6):49-55. [10] HILL D.Laser treatment creates superhydrophobic metals[J].Civil Engineering, 2015, 85(3):38-39. [11] CARDOSO J T, AGUILAR-MORALES A I, ALAMRI S, et al. Superhydrophobicity on hierarchical periodic surface structures fabricated via direct laser writing and direct laser interference patterning on an aluminium alloy[J].Optics and Lasers in Engineering, 2018, 111(4):193-200. [12] BAI W B, LAI N Sh, GUAN M Q, et al. Petal-effect super hydrophobic surface self-assembled from poly (p-phenylene)s[J].European Polymer Journal, 2018, 101(2):12-17. [13] CHEN X H, CHEN M J, MIN Y L, et al. Preparation and electro- chemical properties of superhydrophobic surface of aluminum alloy by hydrothermal method[J]. Journal of Electrochemistry, 2018, 24(1):28-35(in Chinese). [14] YAN Zh P, LIANG X D, SHEN H, et al. Preparation and basic pro-perties of superhydrophobic silicone rubber with micro-nano hierarchical structures formed by picosecond laser-ablated template [J].IEEE Transactions on Dielectrics and Electrical Insulation, 2017, 24(3):1743-1750. doi: 10.1109/TDEI.2017.005924 [15] MOHAMMED MUSTAFA ALJUMAILY, MOHAMMED ABDULHA-KIM ALSAADI, RASEL DAS, et al. Optimization of the synthesis of superhydrophobic carbon nano-materials by chemical vapor deposition[J].Scientific Reports, 2018, 8(1):2778-2779. doi: 10.1038/s41598-018-21051-3 [16] ZHAO Sh G, CHEN Y, MA N, et al. Preparation of superhydrophobic surface and wettability transition of aluminum alloy by electrochemical etching[J].Surface Technology, 2018, 47(3):115-120(in Ch-inese). [17] SHO W, HIROYA M, KOJI F.Drag-reducing performance of obliquely aligned super hydrophobic surface in turbulent channel flow [J].Fluid Dynamics Research, 2017, 49(2):1-20. [18] ZHENG J Y, ZHONG M Q, FENG J. Research progress and industrialization status of self-cleaning surface based on superhydrophobic principle [J].Chemical Industry and Engineering Progress, 2010, 29(2):281-288(in Chinese). [19] LONG J Y, WU Y Ch, GONG D W, et al. Preparation of super hydrophobic copper surface by femtosecond laser and its anti-icing performance [J].Chinese Journal of Lasers, 2015, 42(7):07060002(in Chinese). [20] UROS T, MATEJ H, GREGORCIC P.Transition from superhydrophilic to superhydrophobic state of laser textured stainless steel surface and its effect on corrosion resistance[J].Corrosion Science, 2017, 123(10):21-26. [21] MODESTOV A D, EMELYANENKO K A, EMELYANENKO A M, et al. Application of laser micro- and nano-texturing for the fabrication of superhydrophobic corrosion resistant coatings on aluminum[J].Russian Chemical Bulletin, 2016, 65(11):2607-2611. doi: 10.1007/s11172-016-1625-3 [22] WU H, ZHU L N, YUE W, et al. Research status of tribological properties and hydrophobicity of PTFE composite coatings [J].Materials Review, 2018, A48(1):284-288(in Chinese). [23] ZHANG Y J, DONG L Q, ZHANG Y J, et al. Drag reduction performance of superhydrophobic materials based on numerical simulation[J].Surface Technology, 2016, 45(11):173-179(in Chinese). [24] CAO J Y, ZHANG H Y, LI J H, et al. Research progress and application of superhydrophobic coatings in aerospace field[J].Chemical Engineer, 2017, 31(1):57-60(in Chinese). [25] CAO L R.Study on super-hydrophobic and weather resistant surface of radome [J].Electronics Process Technology, 2016, 37(4):239-242(in Chinese). [26] YE X, WANG Z, ZHOU M, et al. Research of surface micro-structure and anti-coagulant property of pyrolytic carbon induced by laser[J].Laser Technology, 2013, 37(5):696-699(in Chinese). [27] JIANG L, YANG B, LI T J, et al. Binary cooperative complementary nano-scale interfacial materials[J].Pure and Applied Chemistry, 2000, 72(1/2):73-81. [28] GUO Sh H, YU Zh J, LUO B M, et al. Research progress on wetting theory of superhydrophobic surface[J].Materials Review: A Review Rrticle, 2012, A26(3):74-77(in Chinese). [29] LONG J Y, PAN L, FAN P X, et al. Cassie-state stability of metallic superhydrophobic surfaces with various micro/nanostructures produced by a femtosecond laser[J].Langmuir, 2016, 32(4):1065-1072. doi: 10.1021/acs.langmuir.5b04329 [30] WU B.Fabrication and research of metal bionic functional micro-structures by laser[D].Zhenjiang: Jiangsu University, 2011: 73-81(in Chinese). [31] PAN H H, WANG Zh, FAN Zh W, et al. Micro nano structure of superhydrophobic titanium surface induced by femtosecond laser[J].Chinese Journal of Lasers, 2016, 43(8):08020002(in Chinese). [32] WU B, ZHOU M, LI J B, et al. Fabrication of highly adherent stainless steel super hydrophobic surfaces by femtosecond laser combined with hydrothermal method[J].Functional Materials, 2013, 24(4):3658-3662(in Chinese). [33] SONG Y X, WANG C, DONG X R, et al. Controllable superhydrophobic aluminum surfaces with tunable adhesion fabricated by femtosecond laser[J].Optics and Laser Technology, 2018, 102(5):25-31. [34] ELISABETH K, SANDRA S, STEPHAN K, et al. Fabrication of biomimetic fog-collecting superhydrophilic-superhydro phobic surface micropatterns using femtosecond lasers[J].Langmuir, 2018, 34 (9):2933-2941. doi: 10.1021/acs.langmuir.7b03699 [35] SANDRA S, STEPHAN K, MATTHIAS D, et al. Transparent superhydrophobic surfaces with high adhesion generated by the combination of femtosecond laser structuring and wet oxidation[J].Applied Surface Science, 2017, 420(9):550-557. [36] LIU D, WU Y G, HU Y T, et al. Preparation of aluminum based superhydrophobic surface by picosecond laser[J].Laser & Optoelectronics Progress, 2016, 53(10):101408(in Chinese). [37] XIE Zh W, DONG Sh Y, YAN Sh X, et al. Experimental study on morphology control of stainless steel with picosecond laser micro nano processing[J].Laser & Optoelectronics Progress, 2018, 55(3):031402(in Chinese). [38] SUN K, YANG H, XUE W, et al. Anti-biofouling super-hydrophobic surface fabricated by picosecond laser texturing of stainless steel[J].Applied Surface Science, 2018, 436(6):263-267. [39] FATEMA H R, CHISTOPHER M L, BENSON P S, et al. Picosecond laser treatment production of hierarchical structured stainless steel to reduce bacterial fouling[J].Food and Bioproducts Processing, 2018, 109(7):29-40. [40] LAWRENCE J, WAUGH D G.Creating superhydrophobic surface structures via the rose petal effect on stainless steel with a picosecond laser [J].Lasers in Engineering (Old City Publishing), 2017, 37(1/3):125-134. [41] YANG Q B, LIU Sh J, WANG Y T, et al. Nanosecond laser induced super hydrophobic micro nano-structure on aluminum sheet[J].Laser & Optoelectronics Progress, 2017, 55(3):091406(in Chinese). [42] van TA D, DUNN A, WASLEY T J, et al. Laser textured superhydrophobic surfaces and their applications for homogeneous spot deposition[J].Applied Surface Science, 2016, 365(10):153-159. [43] EMELYANENKO A M, SHAGIEVA F M, DOMANTO-VXKY A G, et al. Nanosecond laser micro- and nanotexturing for the design of a superhydrophobic coating robust against long-term contact with water, cavitation, and abrasion[J].Applied Surface Science, 2015, 332(8):513-517. [44] RICO S D, EDWARDSON S P, DEARDEN G.Laser surface texturing of titanium with thermal post-processing for improved wettability properties[J].Procedia CIRP, 2018, 74(6):362-366. [45] OCANA J L, JAGDHEESH R, GARCIA B J J.Direct generation of super-hydrophobic microstructures in metals by UV laser sources in the nanosecond regime[J].Advanced Optical Technologies, 2016, 5(1):87-93. doi: 10.5937/savteh1601087D [46] FU X, ZHANG F, JIANG M, et al. Study on technology and quality of etching copper clad laminate with 1064nm and 355nm laser[J].Laser Technology, 2014, 38(4):435-440(in Chinese). [47] HOU T J, AI J, LIU J G, et al. Selective preparation of metal copper layer on silicate glass by laser surface modification[J].Laser Technology, 2018, 42(2):176-180(in Chinese). [48] YANG Y, WEI X, XIE X Zh, et al. Study on etching process of composite grooves on micro heat pipes with infrared laser[J].Laser Technology, 2018, 42(2):276-281(in Chinese). [49] SHANG X Ch, CAO X K, ZHANG R Zh, et al. Influence of laser wavelength and pulse duration threshold on laser-induced optical damage[J].High Power Laser and Particle Beams, 2008, 20(7):1071-1075(in Chinese). [50] YUAN Ch H, LI X H, TANG D Ch, et al. Influence of wavelength and atmosphere on laser induced microstructure of silicon surface[J].Laser Technology, 2010, 34(5):647-649(in Chinese).