Micro-, nano- and hierarchical structures for superhydrophobicity, self-cleaning and low adhesion

Superhydrophobic surfaces exhibit extreme water-repellent properties. These surfaces with high contact angle and low contact angle hysteresis also exhibit a self-cleaning effect and low drag for fluid flow. Certain plant leaves, such as lotus leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical roughness of their leaf surfaces. The self-cleaning phenomenon is widely known as the ‘lotus effect’. Superhydrophobic and self-cleaning surfaces can be produced by using roughness combined with hydrophobic coatings. In this paper, the effect of micro- and nanopatterned polymers on hydrophobicity is reviewed. Silicon surfaces patterned with pillars and deposited with a hydrophobic coating were studied to demonstrate how the effects of pitch value, droplet size and impact velocity influence the transition from a composite state to a wetted state. In order to fabricate hierarchical structures, a low-cost and flexible technique that involves replication of microstructures and self-assembly of hydrophobic waxes is described. The influence of micro-, nano- and hierarchical structures on superhydrophobicity is discussed by the investigation of static contact angle, contact angle hysteresis, droplet evaporation and propensity for air pocket formation. In addition, their influence on adhesive force as well as efficiency of self-cleaning is discussed.

[1]  B. Bhushan,et al.  Biomimetic superhydrophobic surfaces: multiscale approach. , 2007, Nano letters.

[2]  W. Barthlott,et al.  Thermal evaporation of multi-component waxes and thermally activated formation of nanotubules for superhydrophobic surfaces , 2009 .

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

[4]  Bharat Bhushan,et al.  Towards optimization of patterned superhydrophobic surfaces , 2007, Journal of The Royal Society Interface.

[5]  Se-Jin Choi,et al.  An ultraviolet-curable mold for sub-100-nm lithography. , 2004, Journal of the American Chemical Society.

[6]  Abraham Marmur,et al.  Wetting on Hydrophobic Rough Surfaces: To Be Heterogeneous or Not To Be? , 2003 .

[7]  B. Bhushan,et al.  Superhydrophobicity for Energy Conversion and Conservation Applications , 2008 .

[8]  Stephan Herminghaus,et al.  Roughness-induced non-wetting , 2000 .

[9]  B. Bhushan,et al.  Wetting behaviour during evaporation and condensation of water microdroplets on superhydrophobic patterned surfaces , 2008, Journal of microscopy.

[10]  Wilhelm Barthlott,et al.  Chemistry and Crystal Growth of Plant Wax Tubules of Lotus (Nelumbo nucifera) and Nasturtium (Tropaeolum majus) Leaves on Technical Substrates , 2006 .

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

[12]  Bharat Bhushan,et al.  Nanotribology And Nanomechanics- An Introduction , 2008 .

[13]  Bharat Bhushan,et al.  Multiscale friction mechanisms and hierarchical surfaces in nano- and bio-tribology , 2007 .

[14]  W. Barthlott,et al.  Quantitative assessment to the structural basis of water repellency in natural and technical surfaces. , 2003, Journal of experimental botany.

[15]  Glen McHale,et al.  Dual‐Scale Roughness Produces Unusually Water‐Repellent Surfaces , 2004 .

[16]  C. Extrand,et al.  Model for Contact Angles and Hysteresis on Rough and Ultraphobic Surfaces , 2002 .

[17]  B. Bhushan,et al.  Micro∕nanotribological study of perfluorosilane SAMs for antistiction and low wear , 2005 .

[18]  B. Bhushan,et al.  Surface characterization and adhesion and friction properties of hydrophobic leaf surfaces. , 2006, Ultramicroscopy.

[19]  Bharat Bhushan,et al.  Adhesion and stiction: Mechanisms, measurement techniques, and methods for reduction , 2003 .

[20]  B. Bhushan,et al.  Multiscale Dissipative Mechanisms and Hierarchical Surfaces , 2008 .

[21]  V. Varadan,et al.  Microstereolithography and other Fabrication Techniques for 3D MEMS , 2001 .

[22]  Gareth H. McKinley,et al.  Designing Superoleophobic Surfaces , 2007, Science.

[23]  Neelesh A Patankar,et al.  Mimicking the lotus effect: influence of double roughness structures and slender pillars. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[24]  S. Gorb,et al.  The use of plant waxes as templates for micro- and nanopatterning of surfaces. , 2007, Acta biomaterialia.

[25]  Han Gao,et al.  Combinational template-assisted fabrication of hierarchically ordered nanowire arrays on substrates for device applications , 2006 .

[26]  B. Bhushan,et al.  Wetting transition of water droplets on superhydrophobic patterned surfaces , 2007 .

[27]  Bharat Bhushan,et al.  Biomimetic hierarchical structure for self-cleaning , 2008 .

[28]  B. Bhushan,et al.  Lotus-like biomimetic hierarchical structures developed by the self-assembly of tubular plant waxes. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[29]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[30]  B. Bhushan,et al.  Multiscale effects and capillary interactions in functional biomimetic surfaces for energy conversion and green engineering , 2009, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[31]  Bharat Bhushan,et al.  Fabrication of artificial Lotus leaves and significance of hierarchical structure for superhydrophobicity and low adhesion , 2009 .

[32]  Bharat Bhushan,et al.  Roughness-induced superhydrophobicity: a way to design non-adhesive surfaces , 2008 .

[33]  B. Bhushan,et al.  Surface modification of silicon and polydimethylsiloxane surfaces with vapor-phase-deposited ultrathin fluorosilane films for biomedical nanodevices , 2006 .

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

[35]  M. Madou.  Fundamentals of microfabrication , 1997 .

[36]  Bharat Bhushan,et al.  Self-cleaning efficiency of artificial superhydrophobic surfaces. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[37]  Bharat Bhushan,et al.  Biologically Inspired Surfaces: Broadening the Scope of Roughness** , 2008 .

[38]  Wilhelm Barthlott,et al.  Characterization and Distribution of Water-repellent, Self-cleaning Plant Surfaces , 1997 .

[39]  Chunxiong Luo,et al.  Artificial lotus leaf by nanocasting. , 2005, Langmuir : the ACS journal of surfaces and colloids.

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

[41]  B. Bhushan,et al.  Fabrication and characterization of the hierarchical structure for superhydrophobicity and self-cleaning. , 2009, Ultramicroscopy.

[42]  Bharat Bhushan,et al.  Hydrophobicity, adhesion, and friction properties of nanopatterned polymers and scale dependence for micro- and nanoelectromechanical systems. , 2005, Nano letters.

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

[44]  G de With,et al.  Superhydrophobic films from raspberry-like particles. , 2005, Nano letters.

[45]  K. Wandelt,et al.  Structural analysis of wheat wax (Triticum aestivum, c.v. ‘Naturastar’ L.): from the molecular level to three dimensional crystals , 2005, Planta.

[46]  Bharat Bhushan,et al.  Wetting, adhesion and friction of superhydrophobic and hydrophilic leaves and fabricated micro/nanopatterned surfaces , 2008 .

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

[48]  B. Bhushan,et al.  Nanostructures for superhydrophobicity and low adhesion , 2008 .

[49]  Kerstin Koch,et al.  The hydrophobic coatings of plant surfaces: epicuticular wax crystals and their morphologies, crystallinity and molecular self-assembly. , 2008, Micron.

[50]  Bharat Bhushan,et al.  Hierarchical roughness makes superhydrophobic states stable , 2007 .

[51]  Uwe Thiele,et al.  Wetting of textured surfaces , 2002 .

[52]  Bharat Bhushan,et al.  Roughness optimization for biomimetic superhydrophobic surfaces , 2005 .

[53]  B. Bhushan,et al.  Multiscale Dissipative Mechanisms and Hierarchical Surfaces: Friction, Superhydrophobicity, and Biomimetics , 2008 .

[54]  C. Greiner,et al.  SU-8: a photoresist for high-aspect-ratio and 3D submicron lithography , 2007 .

[55]  W. Barthlott,et al.  Purity of the sacred lotus, or escape from contamination in biological surfaces , 1997, Planta.

[56]  Bharat Bhushan,et al.  Dynamic effects of bouncing water droplets on superhydrophobic surfaces. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[57]  Tomohiro Onda,et al.  Super Water-Repellent Surfaces Resulting from Fractal Structure , 1996 .

[58]  A. Ulman,et al.  Mixed self-assembled monolayers of alkanethiolates on ultrasmooth gold do not exhibit contact-angle hysteresis. , 2005, Journal of the American Chemical Society.

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

[60]  Abraham Marmur,et al.  The Lotus effect: superhydrophobicity and metastability. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[61]  A. Dijk,et al.  Rainfall intensity kinetic energy relationships: a critical literature appraisal , 2002 .

[62]  B. Bhushan.  Principles and Applications of Tribology , 1999 .

[63]  Neelesh A. Patankar,et al.  Multiple Equilibrium Droplet Shapes and Design Criterion for Rough Hydrophobic Surfaces , 2003 .

[64]  B. Bhushan,et al.  Introduction to Tribology , 2002 .

[65]  A. Tuteja,et al.  Design Parameters for Superhydrophobicity and Superoleophobicity , 2008 .

[66]  P. Hoffmann,et al.  Water wetting transition parameters of perfluorinated substrates with periodically distributed flat-top microscale obstacles. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[67]  Bharat Bhushan,et al.  Diversity of structure, morphology and wetting of plant surfaces , 2008 .

[68]  W. Barthlott,et al.  A fast, precise and low-cost replication technique for nano- and high-aspect-ratio structures of biological and artificial surfaces , 2008, Bioinspiration & biomimetics.

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