Adhesion, friction, and compliance of bio-mimetic and bio-inspired structured interfaces

Abstract The remarkable mechanical properties of natural contact surfaces have inspired a great deal of interest and research in recent years. The underlying driver of this interest is the surprising range of surface mechanical properties such as adhesion, friction, and compliance that can be attained primarily by design of near-surface architecture using generic materials properties. A considerable literature has developed spanning the range from biological studies of structure and properties, through models to understand these properties, to development of bio-mimetic and bio-inspired structures, along with theory to understand how structure leads to development of surface mechanical properties. The literature has matured sufficiently that common architectures and principles have emerged, for which we attempt here to present a unified view. The field remains vibrant so we hope that this review can at the same time help in its further progress. Our goal in this paper is to review the field from the point of view of scientists and engineers interested to learn about the architecture, properties, and mechanisms of contacting surfaces in nature and how these might be mimicked to create new materials with unique and interesting properties. We begin with a brief description of natural systems, their architectures and properties, and follow by a discussion of the main bio-mimetic and bio-inspired materials that have been developed recently. We then discuss surface mechanical properties – adhesion, friction, and compliance – how these are related to materials and architectural parameters, and how these properties are measured. Where possible, we provide quantitative models for the relationship between structure and properties. We conclude the paper with a discussion of outlook and future possibilities in this field.

[1]  K. Kendall,et al.  Surface energy and the contact of elastic solids , 1971, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[2]  Robb Thomson,et al.  Lattice Trapping of Fracture Cracks , 1971 .

[3]  James R. Rice,et al.  Elastic Fracture Mechanics Concepts for Interfacial Cracks , 1988 .

[4]  Eduard Arzt,et al.  Patterned Surfaces with Pillars with Controlled 3D Tip Geometry Mimicking Bioattachment Devices , 2007 .

[5]  Lijie Ci,et al.  Gecko-inspired carbon nanotube-based self-cleaning adhesives. , 2008, Nano letters.

[6]  J. D. Gillett,et al.  The Climbing Organ of an Insect, Rhodnius prolixus (Hemiptera; Reduviidae) , 1932 .

[7]  A. Jagota,et al.  Mechanically tunable dry adhesive from wrinkled elastomers , 2008 .

[8]  A. Ghatak Peeling off an adhesive layer with spatially varying modulus. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[9]  G. J. Lake Fatigue and Fracture of Elastomers , 1995 .

[10]  Heinz Schwarz,et al.  Material structure, stiffness, and adhesion: why attachment pads of the grasshopper (Tettigonia viridissima) adhere more strongly than those of the locust (Locusta migratoria) (Insecta: Orthoptera) , 2006, Journal of Comparative Physiology A.

[11]  B. Derjaguin Mechanical properties of the boundary lubrication layer , 1988 .

[12]  A. Jagota,et al.  Model-independent extraction of adhesion energy from indentation experiments. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[13]  Z. Suo,et al.  Mixed mode cracking in layered materials , 1991 .

[14]  R. Full,et al.  Evidence for van der Waals adhesion in gecko setae , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[15]  F. Brochard-Wyart,et al.  Naive model for stick-slip processes , 2007, The European physical journal. E, Soft matter.

[16]  Chung-Yuen Hui,et al.  The effect of preload on the pull-off force in indentation tests of microfibre arrays , 2009, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[17]  A. Crosby,et al.  Controlling polymer adhesion with "pancakes". , 2005, Langmuir : the ACS journal of surfaces and colloids.

[18]  Shravanthi T. Reddy,et al.  Bioinspired Surfaces with Switchable Adhesion , 2007 .

[19]  Patricia McGuiggan,et al.  Fundamental experimental studies in tribology : the transition from interfacial friction of undamaged molecularly smooth surfaces to normal friction with wear , 1990 .

[20]  Chung-Yuen Hui,et al.  Numerical study of shearing of a microfibre during friction testing of a microfibre array , 2011, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[21]  M. Chaudhury,et al.  Shear-induced adhesive failure of a rigid slab in contact with a thin confined film , 2007, The European physical journal. E, Soft matter.

[22]  Friction of soft elastomeric surfaces with a defect , 2007 .

[23]  M. Chaudhury,et al.  Interfacial Rate Processes in Adhesion and Friction , 2000 .

[24]  A. Russell,et al.  The morphological basis of weight-bearing in the scansors of the tokay gecko (Reptilia: Sauria) , 1986 .

[25]  Sachin Goyal,et al.  Buckling of sheared and compressed microfibrils , 2010, Journal of The Royal Society Interface.

[26]  M. D. Thouless,et al.  A parametric study of the peel test , 2008 .

[27]  U Hiller Comparative Studies on the Functional Morphology of 2 Gekkonid Lizards , 1976 .

[28]  K. Johnson,et al.  Adhesion and friction between a smooth elastic spherical asperity and a plane surface , 1997, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[29]  Ashutosh Sharma,et al.  A bioinspired wet/dry microfluidic adhesive for aqueous environments. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[30]  Huajian Gao,et al.  Mechanics of robust and releasable adhesion in biology: bottom-up designed hierarchical structures of gecko. , 2006 .

[31]  G. Whitesides,et al.  The controlled formation of ordered, sinusoidal structures by plasma oxidation of an elastomeric polymer , 1999 .

[32]  Bo N. J. Persson,et al.  On the mechanism of adhesion in biological systems , 2003 .

[33]  Liangti Qu,et al.  Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off , 2008, Science.

[34]  C Majidi,et al.  Effective elastic modulus of isolated gecko setal arrays , 2006, Journal of Experimental Biology.

[35]  Werner Baumgartner,et al.  Biomechanics of ant adhesive pads: frictional forces are rate- and temperature-dependent , 2004, Journal of Experimental Biology.

[36]  K. Shull Contact mechanics and the adhesion of soft solids , 2002 .

[37]  C. Caroli,et al.  Solid friction from stick–slip down to pinning and aging , 2005, cond-mat/0506657.

[38]  Jun Young Chung,et al.  Roles of discontinuities in bio-inspired adhesive pads , 2005, Journal of The Royal Society Interface.

[39]  R. Fearing,et al.  Sliding-induced adhesion of stiff polymer microfibre arrays. I. Macroscale behaviour , 2008, Journal of The Royal Society Interface.

[40]  Bharat Bhushan,et al.  Surface characterization and friction of a bio-inspired reversible adhesive tape , 2006 .

[41]  Pulickel M. Ajayan,et al.  Carbon nanotube-based synthetic gecko tapes , 2007, Proceedings of the National Academy of Sciences.

[42]  A. Russell A contribution to the functional analysis of the foot of the Tokay, Gekko gecko (Reptilia: Gekkonidae) , 1975 .

[43]  A. Jagota,et al.  Active switching of adhesion in a film-terminated fibrillar structure. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[44]  L Mahadevan,et al.  Cooperative adhesion and friction of compliant nanohairs. , 2010, Nano letters.

[45]  A. Geim,et al.  Microfabricated adhesive mimicking gecko foot-hair , 2003, Nature materials.

[46]  W. Barnes Functional Morphology and Design Constraints of Smooth Adhesive Pads , 2007 .

[47]  J. A. Peterson,et al.  Convergent and Alternative Designs in the Digital Adhesive Pads of Scincid Lizards , 1982, Science.

[48]  C Mohrdieck,et al.  Capillary forces between chemically different substrates. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[49]  G. A. D. Briggs,et al.  The effect of tangential force on the contact of elastic solids in adhesion , 1977, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[50]  E. Arzt,et al.  The effect of shape on the adhesion of fibrillar surfaces. , 2008, Acta biomaterialia.

[51]  Kellar Autumn,et al.  Gecko Adhesion: Structure, Function, and Applications , 2007 .

[52]  Robert N. Fisher,et al.  A comparative analysis of clinging ability among pad‐bearing lizards , 1996 .

[53]  Yu Tian,et al.  Frictional adhesion of patterned surfaces and implications for gecko and biomimetic systems. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[54]  Tian Tang,et al.  Can a fibrillar interface be stronger and tougher than a non-fibrillar one? , 2005, Journal of The Royal Society Interface.

[55]  N. Rizzo,et al.  Characterization of the structure and composition of gecko adhesive setae , 2006, Journal of The Royal Society Interface.

[56]  D. F. Ogletree,et al.  Variation of the Interfacial Shear Strength and Adhesion of a Nanometer-Sized Contact , 1996 .

[57]  Peter H. Niewiarowski,et al.  Sticky Gecko Feet: The Role of Temperature and Humidity , 2008, PloS one.

[58]  Eduard Arzt,et al.  Adhesion of bioinspired micropatterned surfaces: effects of pillar radius, aspect ratio, and preload. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[59]  A. Jagota,et al.  Design of biomimetic fibrillar interfaces: 2. Mechanics of enhanced adhesion , 2004, Journal of The Royal Society Interface.

[60]  Shu Yang,et al.  Mechanically switchable wetting on wrinkled elastomers with dual-scale roughness , 2009 .

[61]  Pradeep R. Guduru,et al.  Mode-mixity-dependent adhesive contact of a sphere on a plane surface , 2010, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[62]  D. Maugis Adhesion of spheres : the JKR-DMT transition using a dugdale model , 1992 .

[63]  Nicola Pugno,et al.  Spatulate structures in biological fibrillar adhesion , 2010 .

[64]  Metin Sitti,et al.  Biologically inspired polymer microfibers with spatulate tips as repeatable fibrillar adhesives , 2006 .

[65]  Roland Bennewitz,et al.  Dynamic strain measurements in a sliding microstructured contact , 2008 .

[66]  M. Chaudhury,et al.  The Effects of Molecular Weight and Temperature on the Kinetic Friction of Silicone Rubbers , 2003 .

[67]  F. P. Bowden,et al.  The Friction and Lubrication of Solids , 1964 .

[68]  A. Jagota,et al.  Design of biomimetic fibrillar interfaces: 1. Making contact , 2004, Journal of The Royal Society Interface.

[69]  S. Gorb,et al.  From micro to nano contacts in biological attachment devices , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[70]  E. Arzt,et al.  Discrete contact mechanics of a fibrillar surface with backing layer interactions , 2010 .

[71]  Kellar Autumn,et al.  How Gecko Toes Stick , 2006 .

[72]  A. Jagota,et al.  Compliance of a microfibril subjected to shear and normal loads , 2008, Journal of The Royal Society Interface.

[73]  Hiroshi Tada,et al.  The stress analysis of cracks handbook , 2000 .

[74]  A. Kinloch Adhesion and adhesives , 1987 .

[75]  Christian Fretigny,et al.  Friction and shear fracture of an adhesive contact under torsion. , 2010, Physical review. E, Statistical, nonlinear, and soft matter physics.

[76]  Linda S. Schadler,et al.  Frictional anisotropy of oriented carbon nanotube surfaces , 2005 .

[77]  Nigel E. Stork,et al.  Experimental Analysis of Adhesion of Chrysolina Polita (Chrysomelidae: Coleoptera) on a Variety of Surfaces , 1980 .

[78]  B. Lawn Fracture of Brittle Solids by Brian Lawn , 1993 .

[79]  Y. Jiao,et al.  Adhesion measured on the attachment pads of Tettigonia viridissima (Orthoptera, insecta). , 2000, The Journal of experimental biology.

[80]  R. Ruibal,et al.  The structure of the digital setae of lizards , 1965, Journal of morphology.

[81]  A. Jagota,et al.  A model for static friction in a film-terminated microfibril array , 2009 .

[82]  H. Yao,et al.  Adhesion and sliding response of a biologically inspired fibrillar surface: experimental observations , 2008, Journal of The Royal Society Interface.

[83]  R. Bonser,et al.  The Young's modulus of feather keratin , 1995, The Journal of experimental biology.

[84]  K. Kendall Control of cracks by interfaces in composites , 1975, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[85]  Stanislav N. Gorb,et al.  Ultrastructure of attachment specializations of hexapods (Arthropoda): evolutionary patterns inferred from a revised ordinal phylogeny , 2001 .

[86]  Marion D. Kendall,et al.  The Anatomy of the Tarsi of Schistocerca gregaria Forskål , 2004, Zeitschrift für Zellforschung und Mikroskopische Anatomie.

[87]  Bin Chen,et al.  Pre-tension generates strongly reversible adhesion of a spatula pad on substrate , 2009, Journal of The Royal Society Interface.

[88]  A. Schallamach How Does Rubber Slide , 1971 .

[89]  M. Sitti,et al.  Modeling the soft backing layer thickness effect on adhesion of elastic microfiber arrays , 2008 .

[90]  U. Hiller Untersuchungen zum Feinbau und zur Funktion der Haftborsten von Reptilien , 1968, Zeitschrift für Morphologie der Tiere.

[91]  James H. Dieterich,et al.  Time‐dependent friction in rocks , 1972 .

[92]  David Tabor,et al.  The effect of surface roughness on the adhesion of elastic solids , 1975, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[93]  Ralph Spolenak,et al.  Adhesion design maps for bio-inspired attachment systems. , 2005, Acta biomaterialia.

[94]  R. Full,et al.  Dynamics of geckos running vertically , 2006, Journal of Experimental Biology.

[95]  S. Gorb,et al.  WHEN LESS IS MORE: EXPERIMENTAL EVIDENCE FOR TENACITY ENHANCEMENT BY DIVISION OF CONTACT AREA , 2004 .

[96]  C. A. Brockley,et al.  The role of the rate of application of the tangential force in determining the static friction coefficient , 1973 .

[97]  Ronald S. Fearing,et al.  Towards friction and adhesion from high modulus microfiber arrays , 2007 .

[98]  Thomas A. McMahon,et al.  Biomechanics of the movable pretarsal adhesive organ in ants and bees , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[99]  Metin Sitti,et al.  Adhesion of biologically inspired vertical and angled polymer microfiber arrays. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[100]  Pavel Neuzil,et al.  The nature of the gecko lizard adhesive force. , 2005, Biophysical journal.

[101]  Alfred J. Crosby,et al.  Surface Wrinkles for Smart Adhesion , 2008 .

[102]  George M. Whitesides,et al.  Spontaneous formation of ordered structures in thin films of metals supported on an elastomeric polymer , 1998, Nature.

[103]  Stanislav N. Gorb,et al.  The effect of surface roughness on the adhesion of elastic plates with application to biological systems , 2003 .

[104]  A. Jagota,et al.  Enhanced adhesion and compliance of film-terminated fibrillar surfaces , 2007, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[105]  Carlos Drummond,et al.  Amontons' law at the molecular level , 1998 .

[106]  M. Tagawa,et al.  High friction of a vertically aligned carbon-nanotube film in microtribology , 2004 .

[107]  M. Cutkosky,et al.  Frictional adhesion: a new angle on gecko attachment , 2006, Journal of Experimental Biology.

[108]  M. Sitti,et al.  Gecko-inspired directional and controllable adhesion. , 2008, Small.

[109]  Hyunhyub Ko,et al.  Hybrid core-shell nanowire forests as self-selective chemical connectors. , 2009, Nano letters.

[110]  A two-dimensional model for enhanced adhesion of film-terminated fibrillar interfaces by crack trapping , 2008 .

[111]  Y. Nakayama,et al.  Geckolike high shear strength by carbon nanotube fiber adhesives , 2009 .

[112]  A. V. Pocius,et al.  Adhesion and Adhesives Technology: An Introduction , 1996 .

[113]  B. Persson,et al.  Biological Adhesion for Locomotion on Rough Surfaces: Basic Principles and A Theorist’s View , 2007 .

[114]  B. Hölldobler,et al.  Attachment forces of ants measured with a centrifuge: better 'wax-runners' have a poorer attachment to a smooth surface. , 2000, The Journal of experimental biology.

[115]  A. Jagota,et al.  Mechanism of sliding friction on a film-terminated fibrillar interface. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[116]  K. Wang,et al.  Stress singularities at interface corners in bonded dissimilar isotropic elastic materials , 1971 .

[117]  John R. Rice,et al.  Thermodynamics of the quasi-static growth of Griffith cracks , 1978 .

[118]  M. Thouless,et al.  Elastic Fracture Mechanics of the Peel-Test Geometry , 1992 .

[119]  Yu Tian,et al.  Adhesion and friction in gecko toe attachment and detachment , 2006, Proceedings of the National Academy of Sciences.

[120]  T. Eisner,et al.  Defense by foot adhesion in a beetle (Hemisphaerota cyanea). , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[121]  P. Ajayan,et al.  Tunable friction behavior of oriented carbon nanotube films , 2006 .

[122]  Bruce P. Lee,et al.  A reversible wet/dry adhesive inspired by mussels and geckos , 2007, Nature.

[123]  L. Léger,et al.  Adhesion enhancement through micropatterning at polydimethylsiloxane-acrylic adhesive interfaces. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[124]  Alfred J. Crosby,et al.  Designing Model Systems for Enhanced Adhesion , 2007 .

[125]  Huajian Gao,et al.  Effects of contact shape on the scaling of biological attachments , 2005, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[126]  Shu Yang,et al.  Adhesion Selectivity Using Rippled Surfaces , 2011 .

[127]  A. Jagota,et al.  Adhesion enhancement in a biomimetic fibrillar interface. , 2005, Acta biomaterialia.

[128]  Chung-Yuen Hui,et al.  Effect of stamp deformation on the quality of microcontact printing: theory and experiment. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[129]  Stanislav N. Gorb,et al.  Biological Micro- and Nanotribology: Nature’s Solutions , 2010 .

[130]  Ronald S. Fearing,et al.  Synthetic gecko foot-hair micro/nano-structures as dry adhesives , 2003 .

[131]  Alfred J. Crosby,et al.  Fabricating Microlens Arrays by Surface Wrinkling , 2006 .

[132]  A. Jagota,et al.  Strongly enhanced static friction using a film-terminated fibrillar interface. , 2008, Soft matter.

[133]  Eleanor H. Slifer,et al.  Vulnerable Areas on the Surface of the Tarsus and Pretarsus of the Grasshopper (Acrididae, Orthoptera); with Special Reference to the Arolium , 1950 .

[134]  S. Gorb,et al.  Biomimetic mushroom-shaped fibrillar adhesive microstructure , 2007, Journal of The Royal Society Interface.

[135]  Huajian Gao,et al.  Mechanics of hierarchical adhesion structures of geckos , 2005 .

[136]  Metin Sitti,et al.  Effect of backing layer thickness on adhesion of single-level elastomer fiber arrays , 2007 .

[137]  S. Pispas,et al.  Smart Polymer Surfaces , 2003 .

[138]  S. Gorb,et al.  Shearing of fibrillar adhesive microstructure: friction and shear-related changes in pull-off force , 2007, Journal of The Royal Society Interface.

[139]  C. Hui,et al.  Strength statistics of adhesive contact between a fibrillar structure and a rough substrate , 2008, Journal of The Royal Society Interface.

[140]  B. Newby,et al.  Friction in adhesion , 1998 .

[141]  Ashutosh Sharma,et al.  Microfluidic Adhesion Induced by Subsurface Microstructures , 2007, Science.

[142]  W. Huck,et al.  Surface grafted polymer brushes as ideal building blocks for "smart" surfaces. , 2006, Physical chemistry chemical physics : PCCP.

[143]  Metin Sitti,et al.  Enhanced reversible adhesion of dopamine methacrylamide-coated elastomer microfibrillar structures under wet conditions. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[144]  P. Guduru Detachment of a rigid solid from an elastic wavy surface: Theory , 2007 .

[145]  L. Mahadevan,et al.  Peeling from a biomimetically patterned thin elastic film , 2004, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[146]  Anand Jagota,et al.  Mechanics of Adhesion Through a Fibrillar Microstructure1 , 2002, Integrative and comparative biology.

[147]  J. Koberstein Molecular design of functional polymer surfaces , 2004 .

[148]  A. Jagota,et al.  Effect of fibril arrangement on crack trapping in a film‐terminated fibrillar interface , 2009 .

[149]  A. Thomas,et al.  The strength of highly elastic materials , 1967, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[150]  Costantino Creton,et al.  Pressure-Sensitive Adhesives: An Introductory Course , 2003 .

[151]  C Mohrdieck,et al.  Enhancement of capillary forces by multiple liquid bridges. , 2008, Langmuir : the ACS journal of surfaces and colloids.

[152]  Sharma,et al.  Meniscus instability in a thin elastic film , 2000, Physical review letters.

[153]  Chung-Yuen Hui,et al.  How Compliance Compensates for Surface Roughness in Fibrillar Adhesion , 2005 .

[154]  Oliver Betz,et al.  Performance and adaptive value of tarsal morphology in rove beetles of the genus Stenus (Coleoptera, Staphylinidae). , 2002, The Journal of experimental biology.

[155]  Richard H. C. Bonser,et al.  The Young's modulus of ostrich claw keratin , 2000 .

[156]  Huajian Gao,et al.  Hierarchical modelling of attachment and detachment mechanisms of gecko toe adhesion , 2008, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[157]  Chung-Yuen Hui,et al.  Constraints on Microcontact Printing Imposed by Stamp Deformation , 2002 .

[158]  A. Russell Integrative Functional Morphology of the Gekkotan Adhesive System (Reptilia: Gekkota)1 , 2002, Integrative and comparative biology.

[159]  R S Fearing,et al.  High friction from a stiff polymer using microfiber arrays. , 2006, Physical review letters.

[160]  G. Briggs,et al.  The effect of surface topography on the adhesion of elastic solids , 1977 .

[161]  P. Guduru,et al.  Detachment of a rigid solid from an elastic wavy surface: Experiments , 2007 .

[162]  A. Ruina Slip instability and state variable friction laws , 1983 .

[163]  Stanislav N. Gorb,et al.  Evolution of the dragonfly head-arresting system , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[164]  A. Jagota,et al.  Design of bio-inspired fibrillar interfaces for contact and adhesion — theory and experiments , 2007 .

[165]  AN ALTERNATIVE EXPLANATION OF THE EFFECT OF HUMIDITY IN GECKO ADHESION: STIFFNESS REDUCTION ENHANCES ADHESION ON A ROUGH SURFACE , 2010 .

[166]  A. Evans,et al.  Defect Dependent Adhesion of Fibrillar Surfaces , 2008 .

[167]  A. Gent Adhesion and Strength of Viscoelastic Solids. Is There a Relationship between Adhesion and Bulk Properties , 1996 .

[168]  K. Kendall Strengthening of adhesive joints by dislocations , 1977 .

[169]  Huajian Gao,et al.  Shape insensitive optimal adhesion of nanoscale fibrillar structures. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[170]  S. Gorb,et al.  Spring model of biological attachment pads. , 2006, Journal of theoretical biology.

[171]  Moon Kyu Kwak,et al.  Stretchable, adhesion-tunable dry adhesive by surface wrinkling. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[172]  Matt Wilkinson,et al.  Frictional and elastic energy in gecko adhesive detachment , 2007, Journal of The Royal Society Interface.

[173]  Bharat Bhushan,et al.  Adhesion analysis of two-level hierarchical morphology in natural attachment systems for 'smart adhesion' , 2006 .

[174]  S. Gorb,et al.  Tarsal movements in flies during leg attachment and detachment on a smooth substrate. , 2003, Journal of insect physiology.

[175]  Ralph Spolenak,et al.  Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[176]  Metin Sitti,et al.  Enhanced friction of elastomer microfiber adhesives with spatulate tips , 2007 .

[177]  T. Xie,et al.  Self-Peeling Reversible Dry Adhesive System , 2008 .

[178]  R. Full,et al.  Adhesive force of a single gecko foot-hair , 2000, Nature.

[179]  K. Kendall The adhesion and surface energy of elastic solids , 1971 .

[180]  M. Chaudhury Rate-Dependent Fracture at Adhesive Interface , 1999 .

[181]  E. Rabinowicz The Intrinsic Variables affecting the Stick-Slip Process , 1958 .

[182]  H. Brown,et al.  Creating Smart Polymer Surfaces with Selective Adhesion Properties , 1998 .

[183]  B. Persson,et al.  Sliding Friction: Physical Principles and Applications , 1997 .

[184]  Metin Sitti,et al.  Wet self-cleaning of biologically inspired elastomer mushroom shaped microfibrillar adhesives. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[185]  K. Autumn,et al.  Evidence for self-cleaning in gecko setae. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[186]  A. Jagota,et al.  Effect of rate on adhesion and static friction of a film-terminated fibrillar interface. , 2009, Langmuir : the ACS journal of surfaces and colloids.

[187]  H. Daniels The statistical theory of the strength of bundles of threads. I , 1945, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.