Self-Cleaning of Hydrophobic Rough Surfaces by Coalescence-Induced Wetting Transition.

The superhydrophobic leaves of a lotus plant and other natural surfaces with self-cleaning function have been studied intensively for the development of artificial biomimetic surfaces. The surface roughness generated by hierarchical structures is a crucial property required for superhydrophobicity and self-cleaning. Here, we demonstrate a novel self-cleaning mechanism of textured surfaces attributed to a spontaneous coalescence-induced wetting transition. We focus on the wetting transition as it represents a new mechanism, which can explain why droplets on rough surfaces are able to change from the highly adhesive Wenzel state to the low adhesion Cassie-Baxter state and achieve self-cleaning. In particular, we perform many-body dissipative particle dynamics simulations of liquid droplets (with a diameter of 89 μm) sitting on mechanically textured substrates. We quantitatively investigate the wetting behavior of an isolated droplet as well as coalescence of droplets for both Cassie-Baxter and Wenzel states. Our simulation results reveal that droplets in the Cassie-Baxter state have much lower contact angle hysteresis and smaller hydrodynamic resistance than droplets in the Wenzel state. When small neighboring droplets coalesce into bigger ones on textured hydrophobic substrates, we observe a spontaneous wetting transition from the Wenzel state to the Cassie-Baxter state, which is powered by the surface energy released upon coalescence of the droplets. For superhydrophobic surfaces, the released surface energy may be sufficient to cause a jumping motion of droplets off the surface, in which case adding one more droplet to the coalescence may increase the jumping velocity by one order of magnitude. When multiple droplets are involved, we found that the spatial distribution of liquid components in the coalesced droplet can be controlled by properly designing the overall arrangement of droplets and the distance between them. These findings offer new insights for designing effective biomimetic self-cleaning surfaces by enhancing spontaneous Wenzel-to-Cassie wetting transitions, and additionally, for developing new noncontact methods to manipulate liquids inside the small droplets via multiple-droplet coalescence.

[1]  Shuo Chen,et al.  Spontaneous wetting transition of droplet coalescence on immersed micropillared surfaces , 2018, Applied Mathematical Modelling.

[2]  Qunyang Li,et al.  Revisiting the Critical Condition for the Cassie-Wenzel Transition on Micropillar-Structured Surfaces. , 2018, Langmuir : the ACS journal of surfaces and colloids.

[3]  Shuo Chen,et al.  Ratio dependence of contact angle for droplet wetting on chemically heterogeneous substrates , 2018 .

[4]  Xiao-dong Wang,et al.  Coalescence-Induced Jumping of Two Unequal-Sized Nanodroplets. , 2018, Langmuir : the ACS journal of surfaces and colloids.

[5]  Chensen Lin,et al.  Tuning Drop Motion by Chemical Chessboard-Patterned Surfaces: A Many-Body Dissipative Particle Dynamics Study. , 2018, Langmuir : the ACS journal of surfaces and colloids.

[6]  Zhiguang Guo,et al.  Biomimetic superwettable materials with structural colours. , 2017, Chemical communications.

[7]  R. Kneer,et al.  Coalescence-induced droplet jumping on superhydrophobic surfaces: Effects of droplet mismatch , 2017 .

[8]  Jie Ouyang,et al.  Active learning of constitutive relation from mesoscopic dynamics for macroscopic modeling of non-Newtonian flows , 2017, J. Comput. Phys..

[9]  C. Patrick Collier,et al.  Tuning Superhydrophobic Nanostructures To Enhance Jumping-Droplet Condensation. , 2017, ACS nano.

[10]  G. Ouyang,et al.  An analytical model of nanopatterned superhydrophobic surfaces , 2017, Journal of Coatings Technology and Research.

[11]  Mingjie Liu,et al.  Nature-inspired superwettability systems , 2017 .

[12]  Zhong Lan,et al.  Numerical Simulation of Coalescence-Induced Jumping of Multidroplets on Superhydrophobic Surfaces: Initial Droplet Arrangement Effect. , 2017, Langmuir : the ACS journal of surfaces and colloids.

[13]  P. Meakin,et al.  Many-body dissipative particle dynamics modeling of fluid flow in fine-grained nanoporous shales , 2017 .

[14]  G. Ouyang,et al.  Modeling the Effects of Nanopatterned Surfaces on Wetting States of Droplets , 2017, Nanoscale Research Letters.

[15]  P. Hao,et al.  Numerical simulation of droplet impact on textured surfaces in a hybrid state , 2017, Microfluidics and Nanofluidics.

[16]  Zhiping Liu,et al.  Direction Dependence of Adhesion Force for Droplets on Rough Substrates. , 2017, Langmuir : the ACS journal of surfaces and colloids.

[17]  Yuying Yan,et al.  Wetting transition energy curves for a droplet on a square-post patterned surface. , 2017, Science bulletin.

[18]  Ali Dolatabadi,et al.  Coalescence-induced jumping of micro-droplets on heterogeneous superhydrophobic surfaces , 2017 .

[19]  George Em Karniadakis,et al.  A dissipative particle dynamics method for arbitrarily complex geometries , 2016, J. Comput. Phys..

[20]  J. Weibel,et al.  Coalescence-Induced Jumping of Multiple Condensate Droplets on Hierarchical Superhydrophobic Surfaces , 2016, Scientific Reports.

[21]  A. Mohamed,et al.  Corrosion behavior of superhydrophobic surfaces: A review , 2015 .

[22]  P. Keblinski,et al.  Coalescence-induced jumping of nanoscale droplets on super-hydrophobic surfaces , 2015 .

[23]  Samaneh Farokhirad,et al.  Coalescence-induced jumping of droplet: Inertia and viscosity effects , 2015 .

[24]  Edward Bormashenko,et al.  Progress in understanding wetting transitions on rough surfaces. , 2015, Advances in colloid and interface science.

[25]  Shuo Chen,et al.  Numerical Study on Droplet Sliding across Micropillars. , 2015, Langmuir : the ACS journal of surfaces and colloids.

[26]  E. Wang,et al.  How coalescing droplets jump. , 2014, ACS nano.

[27]  Ziqi Sun,et al.  Fly-eye inspired superhydrophobic anti-fogging inorganic nanostructures. , 2014, Small.

[28]  James J. Feng,et al.  Self-propelled jumping upon drop coalescence on Leidenfrost surfaces , 2014, Journal of Fluid Mechanics.

[29]  G. Watson,et al.  Self-propulsion of dew drops on lotus leaves: a potential mechanism for self cleaning , 2014, Biofouling.

[30]  A. Takahara,et al.  Wetting transition from the Cassie-Baxter state to the Wenzel state on textured polymer surfaces. , 2014, Langmuir : the ACS journal of surfaces and colloids.

[31]  V. Senez,et al.  Acoustic tracking of Cassie to Wenzel wetting transitions. , 2013, Langmuir : the ACS journal of surfaces and colloids.

[32]  Zhen Li,et al.  Three dimensional flow structures in a moving droplet on substrate: A dissipative particle dynamics study , 2013 .

[33]  F. He,et al.  Condensation and jumping relay of droplets on lotus leaf , 2013, 1305.2032.

[34]  Jolanta A Watson,et al.  Self-cleaning of superhydrophobic surfaces by self-propelled jumping condensate , 2013, Proceedings of the National Academy of Sciences.

[35]  Zhong Lan,et al.  Analysis of droplet jumping phenomenon with lattice Boltzmann simulation of droplet coalescence , 2013 .

[36]  N. Morrow,et al.  Physical properties of aqueous glycerol solutions , 2012 .

[37]  Hong Xia,et al.  Recent developments in superhydrophobic surfaces with unique structural and functional properties , 2012 .

[38]  Zhen Li,et al.  Dissipative Particle Dynamics Simulation of Droplet Oscillations in AC Electrowetting , 2012 .

[39]  Kesong Liu,et al.  Bio-Inspired Self-Cleaning Surfaces , 2012 .

[40]  Michael T Harris,et al.  The inexorable resistance of inertia determines the initial regime of drop coalescence , 2012, Proceedings of the National Academy of Sciences.

[41]  Mark C. T. Wilson,et al.  Wettability versus roughness of engineering surfaces , 2011 .

[42]  G. Karniadakis,et al.  Many-body dissipative particle dynamics simulation of liquid/vapor and liquid/solid interactions. , 2011, The Journal of chemical physics.

[43]  Guangming Liu,et al.  Water droplet motion control on superhydrophobic surfaces: exploiting the Wenzel-to-Cassie transition. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[44]  Ya-Pu Zhao,et al.  Size effect on the coalescence-induced self-propelled droplet , 2011 .

[45]  D. Ende,et al.  Electrical switching of wetting states on superhydrophobic surfaces: a route towards reversible Cassie-to-Wenzel transitions. , 2011, Physical review letters.

[46]  J. Boreyko,et al.  Self-propelled dropwise condensate on superhydrophobic surfaces. , 2009, Physical review letters.

[47]  J. Boreyko,et al.  Restoring superhydrophobicity of lotus leaves with vibration-induced dewetting. , 2009, Physical review letters.

[48]  V. Sikka,et al.  Anti-icing superhydrophobic coatings. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[49]  Toshikazu Ebisuzaki,et al.  Coexistence and transition between Cassie and Wenzel state on pillared hydrophobic surface , 2009, Proceedings of the National Academy of Sciences.

[50]  Bharat Bhushan,et al.  Micro-, nano- and hierarchical structures for superhydrophobicity, self-cleaning and low adhesion , 2009, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[51]  Bharat Bhushan,et al.  Biomimetics: lessons from nature–an overview , 2009, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[52]  Lei Jiang,et al.  Bioinspired Design of a Superoleophobic and Low Adhesive Water/Solid Interface , 2009 .

[53]  Bharat Bhushan,et al.  Multifunctional surface structures of plants: An inspiration for biomimetics , 2009 .

[54]  Hongxia Guo,et al.  Simulation study of protein-mediated vesicle fusion. , 2009, The journal of physical chemistry. B.

[55]  Chia-Chung Sun,et al.  Dissipative Particle Dynamics Simulations of Domain Growth and Phase Separation in Binary Immiscible Fluids , 2008 .

[56]  R. Zengerle,et al.  Dynamic capillary wetting studied with dissipative particle dynamics , 2008 .

[57]  B. Bhushan,et al.  Wetting study of patterned surfaces for superhydrophobicity. , 2007, Ultramicroscopy.

[58]  Bharat Bhushan,et al.  Hierarchical roughness optimization for biomimetic superhydrophobic surfaces. , 2007, Ultramicroscopy.

[59]  P. Meakin,et al.  Dissipative particle dynamics simulation of pore‐scale multiphase fluid flow , 2007 .

[60]  Lei Jiang,et al.  Directional adhesion of superhydrophobic butterfly wings. , 2007, Soft matter.

[61]  Bharat Bhushan,et al.  Contact angle, adhesion and friction properties of micro-and nanopatterned polymers for superhydrophobicity , 2006 .

[62]  Bharat Bhushan,et al.  Micro- and nanoscale characterization of hydrophobic and hydrophilic leaf surfaces , 2006 .

[63]  Lichao Gao,et al.  Contact angle hysteresis explained. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[64]  J. Monaghan.  Smoothed particle hydrodynamics , 2005 .

[65]  Xuefeng Gao,et al.  Biophysics: Water-repellent legs of water striders , 2004, Nature.

[66]  Neelesh A Patankar,et al.  Transition between superhydrophobic states on rough surfaces. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[67]  P. B. Warren,et al.  Vapor-liquid coexistence in many-body dissipative particle dynamics. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[68]  Jin Zhai,et al.  Super‐Hydrophobic Surfaces: From Natural to Artificial , 2002 .

[69]  I. Pagonabarraga,et al.  Dissipative particle dynamics for interacting systems , 2001, cond-mat/0105075.

[70]  K. Abe,et al.  Dynamic Contact Angle Measurement of Au(111)−Thiol Self-Assembled Monolayers by the Wilhelmy Plate Method , 2000 .

[71]  Gershon Wolansky,et al.  Apparent contact angles on rough surfaces: the Wenzel equation revisited , 1999 .

[72]  Yasukiyo Ueda,et al.  The Lowest Surface Free Energy Based on −CF3 Alignment , 1999 .

[73]  P. B. Warren,et al.  DISSIPATIVE PARTICLE DYNAMICS : BRIDGING THE GAP BETWEEN ATOMISTIC AND MESOSCOPIC SIMULATION , 1997 .

[74]  P. Español,et al.  Statistical Mechanics of Dissipative Particle Dynamics. , 1995 .

[75]  Jiamin Wan,et al.  Colloid transport in unsaturated porous media , 1994 .

[76]  J. Banavar,et al.  Computer Simulation of Liquids , 1988 .

[77]  P. G. de Gennes,et al.  A model for contact angle hysteresis , 1984 .

[78]  G. Macdougall,et al.  Surface energy relations in liquid/solid systems I. The adhesion of liquids to solids and a new method of determining the surface tension of liquids , 1942, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[79]  R. N. Wenzel.  RESISTANCE OF SOLID SURFACES TO WETTING BY WATER , 1936 .

[80]  David Quéré,et al.  Superhydrophobic states , 2003, Nature materials.

[81]  A. Cassie,et al.  Wettability of porous surfaces , 1944 .

[82]  T. Young.  III. An essay on the cohesion of fluids , 1805, Philosophical Transactions of the Royal Society of London.

[83]  Thomas Young,et al.  An Essay on the Cohesion of Fluids , 1800 .