Bio-inspired Studies on Adhesion of a Thin Film on a Rigid Substrate

107 Pages·2015·3.14 MB·English

by  Zhilong Peng (auth.)

Springer Theses
Recognizing Outstanding Ph.D. Research
Zhilong Peng

Bio-inspired
Studies on
Adhesion of a
Thin Film on a
Rigid Substrate
Springer Theses
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Zhilong Peng
Bio-inspired Studies on
Adhesion of a Thin Film
on a Rigid Substrate
Doctoral Thesis accepted by
Institute of Mechanics,
Chinese Academy of Sciences, China
123
Author Supervisor
Dr. ZhilongPeng Prof. ShaohuaChen
Instituteof Mechanics Instituteof Mechanics
ChineseAcademy ofSciences ChineseAcademy ofSciences
Beijing Beijing
China China
ISSN 2190-5053 ISSN 2190-5061 (electronic)
Springer Theses
ISBN 978-3-662-46954-5 ISBN 978-3-662-46955-2 (eBook)
DOI 10.1007/978-3-662-46955-2
LibraryofCongressControlNumber:2015937017
SpringerHeidelbergNewYorkDordrechtLondon
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Parts of this book have been published in the following articles:
S.H.Chen,Z.L.Peng,Anextensionofthetwo-dimensionalJKRtheorytothecase
with a large contact width. Chinese Physics Letters, 2009, 26(12): 124601.
(Reproduced with permission)
Z.L.Peng,S.H.Chen,A.K.Soh,Peelingbehaviorofabio-inspirednano-filmona
substrate. International Journal of Solids and Structures, 2010, 47(14–15):
1952–1960. (Reproduced with permission)
Z.L. Peng, S.H. Chen, Effects of the relative humidity and water droplet on
adhesionofa bio-inspirednano-film. Colloidsand Surfaces B: Biointerfaces,
2011, 88(2): 717–721. (Reproduced with permission)
Z.L. Peng, S.H. Chen, Effects of surface roughness and film thickness on the
adhesionofabio-inspirednano-film.PhysicalReviewE,2011,83(5):051915.
(Reproduced with permission)
Z.L. Peng, S.H. Chen, The effect of geometry on the adhesive behavior of bio-
inspired fibrils. Soft Matter, 2012, 8(38): 9864–9869. (Reproduced with
permission)
Z.L. Peng, S.H. Chen, Effect of pre-tension on the peeling behavior of a bio-
inspired nano-film and a hierarchical adhesive structure. Applied Physics
Letters, 2012, 101(16): 163702. (Reproduced with permission)
’
Supervisor s Foreword
Adhesionexistseverywhereinoureverydaylife.Itdoesnotplayanimportantrole
in macroscopic scales due to its weakness. However, in nanoscales, micro-forces
dominateadhesionduetothevanderWaalsinteractionorthecapillaryonecannot
be avoided. With the development of nanoscience and nanotechnology, the adhe-
sion problem has attracted the interest of researchers. How to increase or decrease
adhesion has become a key question due to different requirements in different
applications.Forinstance,strongadhesionishelpfulinthefieldofmicroelectronic
packaging,whileadhesionwillresultinfailureoffunctional nanobeamsinMEMS
or NMES. Adhesion will reduce the precision of hardness measurement in nano-
indentation when the tip of nanoindenter comes close to the measured sample.
However, adhesion should be favorable in micromanipulation of medical treat-
ments. Furthermore, reversible adhesion is urgently required in some fields to
realize alteration of strong adhesion and weak one, for example, nanofilm systems
and the adhesion system of a biomimetic microrobot. How to realize controllable
adhesion becomes another important question.
Fortunately, nature as a source of innovation possesses numerous unexpected
functions,fromthebio-materialsthemselvestothesurfacesorinterfaces,afterlong
time evolution and has given mankind a lot of great ideas for designing new
materials or novel structures. For example, airplane and radars benefit from birds
and bats, respectively; waterproof clothings use some inspired ideas from lotus
leaves; teeth and bones give significant help to the structural design of gradient
materials. Similarly, adhesion in nature can be found very easily, such as geckos,
ants,grasshoppersandspiders.Alltheseinsectsoranimalspossessspecialadhesion
abilities and could live in different environments or surfaces. How can they own
such special capacities?
In order to disclose the adhesion mystery existing in biology and find the main
influencing factors of surface adhesion, the adhesion system of geckos’ pads was
observed experimentally and found that each gecko pad consists of hundreds of
thousands of setae and each seta further branches into hundreds of spatulae.
Considering the real profile of a spatula, it looks like a nanofilm.
vii
viii Supervisor’sForeword
Thisthesisfocusesondisclosingmicroadhesionmechanismsadoptedbygeckos,
which is studied mainly with the help of thin-film-substrate systems, considering
the size effect of adhesion length, the end-shape effect of adhesive elements, the
effect of pre-tensions, the effect of surface roughness as well as that of environ-
mental relative humidity on adhesive strength of surfaces and interfaces. All the
results in the present thesis should be helpful not only for the design of advanced
adhesive materials and adhesion systems of biomimetic robots, but also for
resolving adhesion problems in the field of MEMS/NEMS.
Researchers, practitioners as well as graduate students interested in fields of
surface/interface science, design of functional surfaces as well as biomimetic
mechanics could benefit from such a thesis.
Beijing, China Prof. Shaohua Chen
January 2015
Acknowledgments
First of all, I would like to express my heartfelt gratitude to my supervisor,
Prof.ShaohuaChen,whoacceptedmeashisdoctoralstudentandprovidedmewith
someofthemostinterestingproblemsinbiomechanics.Itismygreathonourtobe
able to participate in this project under his constant encouragement and careful
guidance. His instructive advice in both academic and personal matters has bene-
fited me greatly and will walk me through for the rest of my life.
At the same time, special thanks are given to my group members Jianjun Li,
Chao Wang, Yin Yao, Peijian Chen, Biao Feng, Cong Wang, Lei Chen, Mengxin
You, Hao Chen, Guang Xu, Cong Yan and Chunhui Mi for their encouragement
andscientificdiscussion.Theygivememanyinspirationsduringmyresearchwork
and in touching moments in my life.
Last but not least, I am forever grateful to my beloved parents, my parents-in-
law, my brother and sister, especially my lovely wife Lingxiao Sun. They always
stoodbehindmeandsupportedmecontinuouslyduringtheseyears.Thisisforyou.
ix
Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Progress in Surface/Interface Adhesion Mechanics . . . . . . . . . . . 1
1.1.1 Contact Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Biological Adhesion and Bio-inspired Adhesion. . . . . . . . 4
1.2 Contents of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2 Extension of the Two-Dimensional JKR Theory
to the Case with a Large Contact Width. . . . . . . . . . . . . . . . . . . . 19
2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Theoretical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.1 Extension of the JKR Theory . . . . . . . . . . . . . . . . . . . . 22
2.2.2 Extension of the Hertz Theory. . . . . . . . . . . . . . . . . . . . 24
2.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3 Peeling Behavior of a Bio-inspired Nanofilm with Finite Length
on a Rigid Substrate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2 Numerical Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.3 Numerical Results and Discussion . . . . . . . . . . . . . . . . . . . . . . 31
3.3.1 Effect of Adhesion Length . . . . . . . . . . . . . . . . . . . . . . 31
3.3.2 Effect of the Peeling Angle. . . . . . . . . . . . . . . . . . . . . . 33
3.3.3 Effect of Surface Roughness . . . . . . . . . . . . . . . . . . . . . 34
3.3.4 Effects of Young’s Modulus and Thickness
of Nanofilm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
xi