Biological and biomimetic surfaces: adhesion, friction and wetting phenomena

• Stanislav N. Gorb,
• Kerstin Koch and
• Lars Heepe

Beilstein J. Nanotechnol. 2019, 10, 481–482, doi:10.3762/bjnano.10.48

• Keywords: adhesion; air retention; contact mechanics; fluid transport; friction; functional gradients; wetting; This Thematic Series is the continuation of the previous series on the broad topic of biological and bioinspired materials and surfaces [1][2][3]. This collection of articles displays a current

• cross section of recent developments in this highly diverse and interdisciplinary field of research. The articles highlight recent achievements in the understanding of animal and plant surfaces in the broadest context of adhesion, friction, and wetting phenomena on one hand. On the other hand, they

• novel flow and pressure sensors. While most of the articles represent experimental work, two are devoted to theoretical and numerical work on the adhesion of rough brush systems and the friction of functionally graded materials. The metrics mentioned above illustrate that this compilation of articles

Temperature-dependent Raman spectroscopy and sensor applications of PtSe₂ nanosheets synthesized by wet chemistry

• Mahendra S. Pawar and
• Dattatray J. Late

Beilstein J. Nanotechnol. 2019, 10, 467–474, doi:10.3762/bjnano.10.46

• annealed in a vacuum furnace at 170 °C to improve the contact resistance and adhesion of the nanosheets with the substrate. The humidity sensing performance was investigated by exposing the sensor device to various relative humidity (RH) levels ranging from 11.3–97.3% as described in detail previously [26

Advanced scanning probe lithography using anatase-to-rutile transition to create localized TiO₂ nanorods

• Julian Kalb,
• Vanessa Knittel and
• Lukas Schmidt-Mende

Beilstein J. Nanotechnol. 2019, 10, 412–418, doi:10.3762/bjnano.10.40

• adhesion between implants and body tissues [32]. Many of the listed applications could be refined into spatially resolved technologies such as locally controlled photocatalysis for molecule degradation, spatially resolved gas or molecule sensing, gradients on superhydrophilic surfaces with close-meshed

Biocompatible organic–inorganic hybrid materials based on nucleobases and titanium developed by molecular layer deposition

• Leva Momtazi,
• Henrik H. Sønsteby and
• Ola Nilsen

Beilstein J. Nanotechnol. 2019, 10, 399–411, doi:10.3762/bjnano.10.39

• where interaction with the surrounding tissue is controlled at the surface of the material, whereas load is governed by bulk properties. The surface of a material is responsible for interactions with the surrounding tissue by directing protein absorption, which in turn controls cell adhesion and

• by our characterization of density and index of refraction of the films, even after leaching. We have recently compared the bioactivity of these films by growth of goblet cells showing comparable cell adhesion, viability and proliferation as anatase TiO2, however, all being significantly better than

Development of an anti-pollution coating process technology for the application of an on-site PV module

• Sejin Jung,
• Wonseok Choi,
• Jung Hyun Kim and
• Jang Myoun Ko

Beilstein J. Nanotechnol. 2019, 10, 332–336, doi:10.3762/bjnano.10.32

• angle, anti-pollution characteristics, adhesion and hardness of the functional coating films after using different annealing treatment times and methods were measured, and it was confirmed that these characteristics varied depending on the annealing treatment times and methods. Through this, it was

• natural water will significantly improve the economic efficiency of the maintenance of solar power generation systems [7]. Although a self-cleaning coating technique using a photocatalyst has been developed, the durability is poor due to low adhesion and hardness. Also, production is very difficult, an

• using different periods of time. For the fabricated specimens, the contact angle, anti-pollution characteristics, hardness, and adhesion were measured. The process conditions were optimized by analyzing the measurement results. Experimental The coating solution that was used to improve the anti

Interaction of Te and Se interlayers with Ag or Au nanofilms in sandwich structures

• Arkadiusz Ciesielski,
• Lukasz Skowronski,
• Marek Trzcinski,
• Ewa Górecka,
• Wojciech Pacuski and
• Tomasz Szoplik

Beilstein J. Nanotechnol. 2019, 10, 238–246, doi:10.3762/bjnano.10.22

• adhesion of plasmonic metals to almost any ultrasmooth substrate. However, most of the aforementioned elements migrate inside the metal structure as a result of either grain boundary diffusion or segregation [20][21]. This deteriorates both the optical and electrical properties of the plasmonic layers. The

• case of Ge-wetted films reported previously [12][28]. This indicates that the adhesion of the investigated plasmonic metals to Te is very poor. It is also worth noting that the main oscillations in the XRR spectra, related to the thickness of the metal layer, decay much faster than for samples

• deposited with a Ge interlayer – they cannot be observed at angles greater than 2° for silver films and 4° for gold films. This indicates a much higher surface roughness than for the Ge-wetted films. Metal layers deposited on Se exhibit an even worse adhesion – there is almost no change in the grain size

Scanning probe microscopy for energy-related materials

• Rüdiger Berger,
• Benjamin Grévin,
• Philippe Leclère and
• Yi Zhang

Beilstein J. Nanotechnol. 2019, 10, 132–134, doi:10.3762/bjnano.10.12

• the local dielectric distribution based on surface adhesion mapping by SPM [11]. This method is evidently easy in terms of operation and thus has the potential to be widely used. Finally, we want to highlight the contribution “Electrostatic force spectroscopy revealing the degree of reduction of

Pull-off and friction forces of micropatterned elastomers on soft substrates: the effects of pattern length scale and stiffness

• Peter van Assenbergh,
• Marike Fokker,
• Julian Langowski,
• Jan van Esch,
• Marleen Kamperman and
• Dimitra Dodou

Beilstein J. Nanotechnol. 2019, 10, 79–94, doi:10.3762/bjnano.10.8

• substrate between the dimples. Keywords: adhesion; biomimetic micropatterned adhesive; colloidal lithography; friction; pull-off; soft substrate; Introduction Pull-off and friction forces of micropatterned adhesives as a function of geometry, feature size, and stiffness Over the last few decades

• rigid glass substrate [24]. On very soft substrates (Young’s modulus E ≈ 10 kPa), the indentation depth of microscale features is determined by a balance between the elastic properties of the substrate and the substrate–micropattern adhesion effects [25]. The length scale at which these adhesion effects

• adhesive micropatterns with various stiffness degrees. Moreover, we expanded the fabrication method in order to fabricate two dimple sizes: sub-microscale and microscale. Finally, considering the positive effect of a terminal layer on the adhesion of micropatterns, we expanded the fabrication process in

A comparison of tarsal morphology and traction force in the two burying beetles Nicrophorus nepalensis and Nicrophorus vespilloides (Coleoptera, Silphidae)

• Liesa Schnee,
• Benjamin Sampalla,
• Josef K. Müller and
• Oliver Betz

Beilstein J. Nanotechnol. 2019, 10, 47–61, doi:10.3762/bjnano.10.5

• . Our results suggest that even subtle differences in the adhesion-mediating secretion in closely related species might result in qualitative performance shifts. Keywords: adhesion; friction; Insecta; locomotion; tarsus; Introduction Although mostly ground dwelling [1], burying beetles (Silphidae) of

• of insect adhesion have been performed with ‘good plant climbers’ [4][5][6][7]. Although burying beetles can be observed climbing plants to reach a better position from which to start flying to their carrion resources [1], they do not primarily use their tarsi in the context of plant climbing

• hairs. The precise way in which the viscosity of the adhesion-mediating tarsal secretion of insects influences friction performance remains the subject of debate. Nevertheless, subtle differences in the hydrocarbon profiles of the tarsal secretion, probably leading to a decreased fluidity in N

Contact splitting in dry adhesion and friction: reducing the influence of roughness

• Jae-Kang Kim and
• Michael Varenberg

Beilstein J. Nanotechnol. 2019, 10, 1–8, doi:10.3762/bjnano.10.1

• , stronger adhesion, and a more uniform stress distribution with higher tolerance to defects. However, while it is widely believed that contact splitting helps to mitigate the negative effects of roughness on adhesion- and friction-based attachment, no decisive experimental validation of this hypothesis has

• been performed so far for thin-film-based adhesives. To this end, we report on the behavior of original and split, wall-shaped adhesive microstructures on different surfaces ranging across four orders of magnitude in roughness. Our results clearly demonstrate that the adhesion- and friction-driven

• adhesion; surfaces; tribology; Introduction Biological attachment systems based on thin-film adhesion have drawn significant interest during the last two decades because of their ability to operate on nearly any surface, their efficient control of detachment and their high resistance to contamination [1

A new bioinspired method for pressure and flow sensing based on the underwater air-retaining surface of the backswimmer Notonecta

• Matthias Mail,
• Adrian Klein,
• Horst Bleckmann,
• Anke Schmitz,
• Torsten Scherer,
• Peter T. Rühr,
• Goran Lovric,
• Robin Fröhlingsdorf,
• Stanislav N. Gorb and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2018, 9, 3039–3047, doi:10.3762/bjnano.9.282

• detaching from the surface of N. glauca. The deformation of the droplet indicates adhesion between the droplet and the pin-setae. This suggests that the pin-setae penetrate the air–water interface and become wet. b) Water droplet lying on the club-setae of the superhydrophobic surface of N. glauca. c

In situ characterization of nanoscale contaminations adsorbed in air using atomic force microscopy

• Jesús S. Lacasa,
• Lisa Almonte and
• Jaime Colchero

Beilstein J. Nanotechnol. 2018, 9, 2925–2935, doi:10.3762/bjnano.9.271

• sides of the tip may be huge if two plane sides of the probe-tip and the sample-tip interact together. In a sense, such a tip-probe versus tip-sample system has an infinite effective radius R resulting in a huge adhesion force (Fadh = 4πR·γ·cos(φ), with γ being the surface energy of water and φ being

The effect of flexible joint-like elements on the adhesive performance of nature-inspired bent mushroom-like fibers

• Elliot Geikowsky,
• Serdar Gorumlu and
• Burak Aksak

Beilstein J. Nanotechnol. 2018, 9, 2893–2905, doi:10.3762/bjnano.9.268

• and the directional adhesion properties to attach strongly and efficiently to a surface. Recent studies have revealed that many of such organisms also feature materials with a graded elastic modulus that is tailored towards improving the contact area without sacrificing the fiber density. In

• : bent fibers; bioinspired dry adhesives; gecko adhesion; joint-like element; mushroom-like fibers; Introduction Most natural organisms that rely on temporary adhesion to surfaces for survival do so using tiny, densely packed fibers [1][2]. These fibers vary in dimension and material properties

• depending on the organism that bears them. They form an adhesive contact with the opposing surface, cumulatively providing a large enough force to support the organism’s body weight [3][4]. The strength of adhesion primarily depends on two quantities, the compliance of the fiber array as well as the number

Biomimetic surface structures in steel fabricated with femtosecond laser pulses: influence of laser rescanning on morphology and wettability

• Camilo Florian Baron,
• Alexandros Mimidis,
• Daniel Puerto,
• Evangelos Skoulas,
• Emmanuel Stratakis,
• Javier Solis and
• Jan Siegel

Beilstein J. Nanotechnol. 2018, 9, 2802–2812, doi:10.3762/bjnano.9.262

• surface structures; laser rescanning; steel; wettability; Introduction Complex structures found in nature often present properties that are attractive for applications in science and technology. The hydrophobicity found at the lotus leaf surface [1], the exceptional adhesion capability of gecko feet [2

Optimization of Mo/Cr bilayer back contacts for thin-film solar cells

• Nima Khoshsirat,
• Fawad Ali,
• Vincent Tiing Tiong,
• Mojtaba Amjadipour,
• Hongxia Wang,
• Mahnaz Shafiei and
• Nunzio Motta

Beilstein J. Nanotechnol. 2018, 9, 2700–2707, doi:10.3762/bjnano.9.252

• .9.252 Abstract Molybdenum (Mo) is the most commonly used material as back contact in thin-film solar cells. Adhesion of Mo film to soda–lime glass (SLG) substrate is crucial to the performance of solar cells. In this study, an optimized bilayer structure made of a thin layer of Mo on an ultra-thin

• chromium (Cr) adhesion layer is used as the back contact for a copper zinc tin sulfide (CZTS) thin-film solar cell on a SLG substrate. DC magnetron sputtering is used for deposition of Mo and Cr films. The conductivity of Mo/Cr bilayer films, their microstructure and surface morphology are studied at

• different deposition powers and working pressures. Good adhesion to the SLG substrate has been achieved by means of an ultra-thin Cr layer under the Mo layer. By optimizing the deposition conditions we achieved low surface roughness, high optical reflectance and low sheet resistivity while we could decrease

Characterization of the microscopic tribological properties of sandfish (Scincus scincus) scales by atomic force microscopy

• Weibin Wu,
• Christian Lutz,
• Simon Mersch,
• Richard Thelen,
• Christian Greiner,
• Guillaume Gomard and
• Hendrik Hölscher

Beilstein J. Nanotechnol. 2018, 9, 2618–2627, doi:10.3762/bjnano.9.243

• sandfish due to their ability to swim in loose, aeolian sand. Some studies report that this fascinating property of sandfish is accompanied by unique tribological properties of their skin such as ultra-low adhesion, friction and wear. The majority of these reports, however, is based on experiments

• conducted with a non-standard granular tribometer. Here, we characterise microscopic adhesion, friction and wear of single sandfish scales by atomic force microscopy. The analysis of frictional properties with different types of probes (sharp silicon tips, spherical glass tips and sand debris) demonstrates

• , it is highly unlikely that the surface structure of the scales is responsible for the observed low abrasion. Baumgartner and co-workers [10][11][16] measured adhesion by atomic force microscopy (AFM) on scales of S. scincus and observed extremely low values. They analysed the chemical composition of

Friction reduction through biologically inspired scale-like laser surface textures

• Johannes Schneider,
• Vergil Djamiykov and
• Christian Greiner

Beilstein J. Nanotechnol. 2018, 9, 2561–2572, doi:10.3762/bjnano.9.238

• were reported [15][16][27][28]. This is true for the dimple diameter [15][27][28], as well as for the dimple depth [16][28]. Size effects are a common phenomenon in materials science and have been found to influence mechanical and magnetic as well as surface properties like adhesion [38][39][40][41

Cytotoxicity of doxorubicin-conjugated poly[N-(2-hydroxypropyl)methacrylamide]-modified γ-Fe₂O₃ nanoparticles towards human tumor cells

• Zdeněk Plichta,
• Yulia Kozak,
• Rostyslav Panchuk,
• Viktoria Sokolova,
• Matthias Epple,
• Lesya Kobylinska,
• Pavla Jendelová and
• Daniel Horák

Beilstein J. Nanotechnol. 2018, 9, 2533–2545, doi:10.3762/bjnano.9.236

• stability in aqueous media and limited internalization by the cells, however, enabled adhesion to the cell surface. While the neat PHPMA-coated particles proved to be non-toxic, doxorubicin-conjugated particles exhibited enhanced cytotoxicity in both drug-sensitive and drug-resistant tumor cells compared to

• , however, still under study. It can be concluded that the newly designed γ-Fe2O3@P(HPMA-MMAA)-Dox nanoparticles are highly promising for the delivery of cancer medications into tumors, offering enhanced cell adhesion, increased apoptosis, minimal immunogenicity, lipid peroxidation, DNA damage, and reduced

Evidence of friction reduction in laterally graded materials

• Roberto Guarino,
• Gianluca Costagliola,
• Federico Bosia and
• Nicola Maria Pugno

Beilstein J. Nanotechnol. 2018, 9, 2443–2456, doi:10.3762/bjnano.9.229

• , the method of dimensionality reduction [24][25] has been extended to the axisymmetric frictionless contact of elastically graded materials [26], and solutions are also provided in the presence of adhesion [27]. In all these cases, the elastic gradients are considered with respect to the depth, with an

ZnO-nanostructure-based electrochemical sensor: Effect of nanostructure morphology on the sensing of heavy metal ions

• Marina Krasovska,
• Vjaceslavs Gerbreders,
• Irena Mihailova,
• Andrejs Ogurcovs,
• Eriks Sledevskis,
• Andrejs Gerbreders and
• Pavels Sarajevs

Beilstein J. Nanotechnol. 2018, 9, 2421–2431, doi:10.3762/bjnano.9.227

• obtaining ZnO nanostructures in various morphologies, such as ZnO nanoneedles, nanorods, nanotubes, nanoplates, etc. Also the purpose of our previous research was to identify optimal growth parameters for obtaining a homogeneous, dense, well-aligned nanostructured ZnO coating with good adhesion to hard

• with a ZnO seed layer in order to provide adhesion of the nanostructured ZnO film to the glass surface, as well as epitaxial growth and the vertical alignment of nanostructures. It was prepared by dip coating using 5 mM zinc acetate (Zn(O2CCH3)2) solution in ethanol. The seed layer film was dried in a

Adhesive contact of rough brushes

• Qiang Li and
• Valentin L. Popov

Beilstein J. Nanotechnol. 2018, 9, 2405–2412, doi:10.3762/bjnano.9.225

• structure and an elastic half-space is numerically simulated using the fast Fourier transform (FFT)-based boundary element method and the mesh-dependent detachment criterion of Pohrt and Popov. The problem is of interest in light of the discussion of the role of contact splitting in the adhesion strength of

• gecko feet and structured biomimetic materials. For rigid brushes, the contact splitting does not enhance adhesion even if all pillars of the brush are positioned at the same height. Introducing statistical scatter of height leads to a further decrease of the maximum adhesive strength. At the same time

• modification due to finite size effect of the brush. Keywords: adhesion; brushes; contact splitting; pressure sensitive adhesion; roughness; Introduction The study of adhesive contacts has been largely enhanced by studies of the extremely effective adhesion pads of geckos [1]. For example, the adhesion can

High-throughput micro-nanostructuring by microdroplet inkjet printing

• Hendrikje R. Neumann and
• Christine Selhuber-Unkel

Beilstein J. Nanotechnol. 2018, 9, 2372–2380, doi:10.3762/bjnano.9.222

• BCML can be biofunctionalized such that they serve as biomimetic anchorage sites for cell adhesion molecules, whereby their spacing has been shown to be highly decisive for cell adhesion [14]. Still, the anchorage site spacing required for cell adhesion depends on the chemistry of a particular adhesion

• ligand [15]. It has even been reported that cells can respond to differences in ligand spacing as small as 1 nm across the cell diameter [16]. Therefore, the fabrication of complex patterns of gold nanoparticles is highly relevant in the context of the biomimicry of cell adhesion environments. Whereas

Nanotribology

• Enrico Gnecco,
• Susan Perkin,
• Andrea Vanossi and
• Ernst Meyer

Beilstein J. Nanotechnol. 2018, 9, 2330–2331, doi:10.3762/bjnano.9.217

• : nanotribology; nanoadhesion; nanofriction; Nanotribology is a young and dynamic field of research which aims to investigate friction, wear and adhesion phenomena down to the nanometer scale. Since these phenomena occur in all natural, artificial or conceptual situations involving two surfaces (at least) in

Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

• Valerio F. Gili,
• Lavinia Ghirardini,
• Davide Rocco,
• Giuseppe Marino,
• Ivan Favero,
• Iännis Roland,
• Giovanni Pellegrini,
• Lamberto Duò,
• Marco Finazzi,
• Luca Carletti,
• Andrea Locatelli,
• Aristide Lemaître,
• Dragomir Neshev,
• Costantino De Angelis,
• Giuseppe Leo and
• Michele Celebrano

Beilstein J. Nanotechnol. 2018, 9, 2306–2314, doi:10.3762/bjnano.9.215

• SiOx are deposited on the surface via plasma-enhanced chemical vapor deposition (PECVD) to later improve the adhesion of the negative-tone HSQ resist on the III–V layer. A first positive-tone lithography step with PMMA resist is performed to realize the alignment structures, followed by electron beam

Nanoscale characterization of the temporary adhesive of the sea urchin Paracentrotus lividus

• Ana S. Viana and
• Romana Santos

Beilstein J. Nanotechnol. 2018, 9, 2277–2286, doi:10.3762/bjnano.9.212

• terms of adhesion forces, higher values were obtained in dry conditions, reaching up to 50 nN. Under native conditions, lower adhesive forces were obtained (up to 500 pN) but the adhesive seemed to behave like a functional amyloid, as evidenced by the recorded characteristic sawtooth force–extension

• . Keywords: adhesive footprint; atomic force microscopy; nanomechanical properties; sea urchin; temporary adhesion; Introduction Unlike the thin homogeneous films that are typical for adhesives produced by humans, biological adhesives present complex hierarchical micro- and nanostructures. Among marine

• such as Entobdella solae temporarily attach to fish skin using anterior pads located in the head [1]. Adhesion is brought about by interaction between two kinds of glandular secretions which are extruded together to form the adhesive [11]. The later consists of a network of highly insoluble