When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

• Niall Crawford,
• Thomas Endlein,
• Jonathan T. Pham,
• Mathis Riehle and
• W. Jon P. Barnes

Beilstein J. Nanotechnol. 2016, 7, 2116–2131, doi:10.3762/bjnano.7.201

• ]. With slip angles, an angle of 90° represents the maximum friction force that this technique can measure. One might therefore predict that, if a frog did not slip by 90° then it should not slip at all, but simply fall from the platform when the angle for maximum adhesion was reached. This occurred in

• friction force was related to the density of asperities, and thus could have been caused by interlocking of the 2 µm diameter asperities with the 1–2 µm channels between the toe pad epithelial cells. An alternative explanation for this increase in friction relates to the fact that the toe pad epithelium

• can be thought of as a viscoelastic material and, as such, will dissipate energy when it is deformed [29]. Such energy would contribute to the friction force on rough surfaces. Indeed, such viscoelastic deformations can also enhance adhesion [30]. For larger roughnesses on the polishing disc surfaces

Generalized Hertz model for bimodal nanomechanical mapping

• Aleksander Labuda,
• Marta Kocuń,
• Waiman Meinhold,
• Deron Walters and
• Roger Proksch

Beilstein J. Nanotechnol. 2016, 7, 970–982, doi:10.3762/bjnano.7.89

• ][5], force modulation [6][7], phase imaging [8][9], loss tangent imaging [10], friction force microscopy [11], creep compliance [12], shear modulation force microscopy [13], pulsed force microscopy [14] and torsional approaches [15]. These techniques can be broadly classified as either “parametric

Probing fibronectin–antibody interactions using AFM force spectroscopy and lateral force microscopy

• Andrzej J. Kulik,
• Małgorzata Lekka,
• Kyumin Lee,
• Grazyna Pyka-Fościak and
• Wieslaw Nowak

Beilstein J. Nanotechnol. 2015, 6, 1164–1175, doi:10.3762/bjnano.6.118

• perpendicular (normal) to the surface and a relative position on a sample. In the AFM-FS measurement, force curves are recorded point-by-point, requiring a precise but tedious and very time consuming procedure. Lateral force microscopy (LFM), also called friction force microscopy (FFM) is another operational

• -functionalized) cantilever. As shown in Figure 2, the fibronectin molecules had a regular globular shape and were uniformly distributed over the entire scanned area. The FN height ranged from 0.5 to 3.5 nm with a mean value of 2.4 ± 0.9 nm. Dependence of friction force on normal load The frictional interaction

• between surfaces observed on the macroscale is typically modelled using Amonton’s law, where a frictional force is linearly dependent on a load force. The proportionality factor is the constant friction coefficient. To verify whether any friction force is observed between the FN-coated surface and the FN

Stick–slip behaviour on Au(111) with adsorption of copper and sulfate

• Nikolay Podgaynyy,
• Sabine Wezisla,
• Christoph Molls,
• Shahid Iqbal and
• Helmut Baltruschat

Beilstein J. Nanotechnol. 2015, 6, 820–830, doi:10.3762/bjnano.6.85

• the interpretation that the tip penetrates the electrochemical double layer at this point. At the potential (or point) of zero charge (pzc), stick–slip resolution persists at all normal forces investigated. Keywords: AFM; friction; friction force microscopy; nanotribology; underpotential deposition

• friction forces on single crystal electrodes under electrochemical conditions. In [10][11] we investigated the effect of copper under potential deposition (UPD) on Au(111) and Pt(111) on friction and found an increase in friction force after adsorption of a sub- or monolayer of copper. A particularly high

• exerted by the tip. The friction force on UPD copper in presence of chloride is much smaller than in sulfuric acid solution. Upon the adsorption of sulfate ions on Au(111), we observed a considerable increase in friction force [10][13]. Bennewitz, Hausen and Gosvami showed that stick–slip resolution can

Aquatic versus terrestrial attachment: Water makes a difference

• Petra Ditsche and
• Adam P. Summers

Beilstein J. Nanotechnol. 2014, 5, 2424–2439, doi:10.3762/bjnano.5.252

• ]. In terrestrial systems, we can distinguish between two cases in which friction plays different roles in adhesion, namely dry and wet. Dry friction occurs between dry, clean surfaces in a very dry atmosphere. In this case, the friction force is usually proportional to the real contact area, as it is

Probing viscoelastic surfaces with bimodal tapping-mode atomic force microscopy: Underlying physics and observables for a standard linear solid model

• Santiago D. Solares

Beilstein J. Nanotechnol. 2014, 5, 1649–1663, doi:10.3762/bjnano.5.176

• a ‘friction’ force opposite to its motion, regardless of the direction in which it travels (upward or downward). In contrast, in the SLS model, the dissipation is a consequence of the simple fact that the work done by the cantilever against the surface during the approach is greater than the work

Physical principles of fluid-mediated insect attachment - Shouldn’t insects slip?

• Jan-Henning Dirks

Beilstein J. Nanotechnol. 2014, 5, 1160–1166, doi:10.3762/bjnano.5.127

• mediating fluid to friction forces can be estimated by using a simple model of a mercury thread moving through a glass tube [55]. For a simplified model with a circular contact area with radius r, and α1 and α2 as the leading and trailing edge contact angles [57], the retentive “friction” force F acting on

• account the viscosity of the mediating fluid layer. Two parallel smooth surfaces with a distance of h sliding at a velocity v relative to each other generate the friction force where ηeff is the effective viscosity of the mediating fluid layer and A the size of the contact area. Again, similar to the time

Dry friction of microstructured polymer surfaces inspired by snake skin

• Martina J. Baum,
• Lars Heepe,
• Elena Fadeeva and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2014, 5, 1091–1103, doi:10.3762/bjnano.5.122

• beyond these parameters, also a critical stiction length due to microstructure dimension is of importance. Furthermore Sondhauß et al. [38] investigated the influence of microstructures in a smaller dimension on frictional properties. By using a friction force microscope, they have shown that the

A nanometric cushion for enhancing scratch and wear resistance of hard films

• Katya Gotlib-Vainshtein,
• Olga Girshevitz,
• Chaim N. Sukenik,
• David Barlam and
• Sidney R. Cohen

Beilstein J. Nanotechnol. 2014, 5, 1005–1015, doi:10.3762/bjnano.5.114

• µN. Applied load vs friction force curves and µ evaluated by lateral force microscopy. FEA model for 7 nm titania layer for 10 nN force showing z-component of global stress distribution for a) PDMS substrate, and b) Si substrate. Inset shows the deformation, with z enlarged by 7× for PDMS and 70× for

Manipulation of nanoparticles of different shapes inside a scanning electron microscope

• Boris Polyakov,
• Sergei Vlassov,
• Leonid M. Dorogin,
• Jelena Butikova,
• Mikk Antsov,
• Sven Oras,
• Rünno Lõhmus and
• Ilmar Kink

Beilstein J. Nanotechnol. 2014, 5, 133–140, doi:10.3762/bjnano.5.13

• oscillation parallel to the manipulation direction is more preferable for the manipulation of NPs because of the better control over the NP movement and a more accurate estimation of the force. Static friction analysis. To analyze the results of the experimentally measured static friction force of the NPs, we

• calculated the friction force values, Ffriction, by using a simple relation: where τ is the interfacial shear stress/strength and A is the contact area [26]. The shear strength is defined as an ultimate shear stress τ before the object is displaced, and can be estimated by using the relation τtheo = G*/Z

• parameters were used: E1 = 71.7 GPa, ν1 = 0.17, E2 = 78 GPa, ν2 = 0.36, Z = 30 [4]. The static friction force values for Au NPs of different geometries were calculated according to Equation 1 and presented in Table 1. The detailed calculation is given in Supporting Information File 1. Analyzing the

Effect of normal load and roughness on the nanoscale friction coefficient in the elastic and plastic contact regime

• Aditya Kumar,
• Thorsten Staedler and
• Xin Jiang

Beilstein J. Nanotechnol. 2013, 4, 66–71, doi:10.3762/bjnano.4.7

• plasticity index and contact load. Their recent work [10] showed that the static friction coefficient (ratio of friction force and normal load) depends on the external force and nominal contact area. Recently, FEM based work by Flores et al. [11] showed that the apparent friction coefficient at a low level

• coefficient decreases here with increasing load following Hertzian behavior. Another study [12] shows the effect of normal load on the friction coefficient. In this work the friction coefficient is defined as the slope of the friction force with respect to normal load [13]; it is observed that the coefficient

• of the behavior of the friction force or friction coefficient with respect to the contact regime has been achieved, i.e., the effect of load and/or roughness on the friction coefficient is not fully understood for different contact modes. Today the technological progress in scanning-probe techniques

Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

• Dave Maharaj and
• Bharat Bhushan

Beilstein J. Nanotechnol. 2012, 3, 759–772, doi:10.3762/bjnano.3.85

• single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the

• used to push the nanoparticle laterally (lateral manipulation). Manipulation studies of nanoparticles, with the aid of an AFM have shown that there is a contact-area dependence of the friction force. Several types of nanoparticles with reported diameters, such as latex spheres (80–100 nm) [28], Sb

• ]. In the study by Mougin and co-workers [32], it was found that Au nanoparticles could not be moved in an ultrahigh vacuum (UHV) as compared to an ambient environment under otherwise identical manipulating conditions. Palacio and Bhushan [31] found that for larger nanoparticles, the friction force was

Friction and durability of virgin and damaged skin with and without skin cream treatment using atomic force microscopy

• Bharat Bhushan,
• Si Chen and
• Shirong Ge

Beilstein J. Nanotechnol. 2012, 3, 731–746, doi:10.3762/bjnano.3.83

• friction was calibrated by the method described by Bhushan [33]. The friction force measurements were made over a scan length of 10 µm and at a scan rate of 1 Hz at various increments of normal load ranging from 25 nN to 250 nN. By plotting the friction force as a function of the normal load, an average

• environment over a stroke length of 10 mm and at a velocity of 0.4 mm/s and at a normal load ranging from 20 mN to 60 mN, unless otherwise noted. A sapphire ball with a 1.5 mm radius and surface roughness of about 2 nm RMS was fixed in a stationary holder. The normal load and friction force were measured with

• and lead to a lower contact angle. Figure 5 shows curves of friction force as a function of normal load for virgin rat and pig skin. An average value of coefficient of friction was obtained from the slope of the fitted line of the data. The intercept on the horizontal axis of normal load is the

Current-induced forces in mesoscopic systems: A scattering-matrix approach

• Niels Bode,
• Silvia Viola Kusminskiy,
• Reinhold Egger and
• Felix von Oppen

Beilstein J. Nanotechnol. 2012, 3, 144–162, doi:10.3762/bjnano.3.15

• the scattering matrix and its parametric derivatives. These are given by Equation 39 for the mean force Fν(X), Equation 42 for the correlator Dνν′(X) of the stochastic force ξν, and Equation 47, and Equation 50 for the two kinds of forces (dissipative-friction force and effective “Lorentz” force, as

Current-induced dynamics in carbon atomic contacts

• Jing-Tao Lü,
• Tue Gunst,
• Per Hedegård and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2011, 2, 814–823, doi:10.3762/bjnano.2.90

• properties when exchanging modes(n ↔ m) and electrodes(α ↔ β), and which are helpful when examining the terms in Equation 11, which are summarized in the following: Friction – The first term in Equation 11 is imaginary and symmetric in mode index m,n. It describes the friction force due to the generation of

• electron–hole pairs in the electronic environment by the ionic motion. This process exists even in equilibrium [31]. For slowly varying AL/R with energy as compared to the vibrational energies (wide-band limit) we obtain the simple time-local electron friction force, , with NC (wind) force – The second

The description of friction of silicon MEMS with surface roughness: virtues and limitations of a stochastic Prandtl–Tomlinson model and the simulation of vibration-induced friction reduction

• W. Merlijn van Spengen,
• Viviane Turq and
• Joost W. M. Frenken

Beilstein J. Nanotechnol. 2010, 1, 163–171, doi:10.3762/bjnano.1.20

• frequency. The results obtained agree very well with measurement data reported previously. Keywords: MEMS; microscale friction reduction; normal force modulation; stochastic Prandtl–Tomlinson model; surface roughness; Introduction With the invention of the friction force microscope (FFM) by Mate et al. [1

• lateral force only when sliding in two directions takes place (Figure 3). From this dissipated energy, we calculated the average friction force such as plotted in the succeeding graphs, by dividing this energy by the distance slid. In the measurements used for this paper, we systematically varied the

• normal force, while keeping the support position speed and environmental conditions constant. This resulted in a friction force that is more or less linear in the normal force, with a friction coefficient of 0.27 at a temperature of 27 °C and 25% RH (Figure 4). The fact that the friction force becomes

A collisional model for AFM manipulation of rigid nanoparticles

• Enrico Gnecco

Beilstein J. Nanotechnol. 2010, 1, 158–162, doi:10.3762/bjnano.1.19

• and r' is the first derivative of r(φ) with respect to φ (Figure 1b). In contact mode the tip hits the particle along the x direction and the force F can be oriented as in tapping mode only if the static friction force f between tip and particle is high enough to prevent sliding along the island profile

• , where a ‘mean free path’ d of the nanoparticles was introduced. If the friction force between particle and substrate decreases, and consequently the distance d increases, then the pathway of the nanoparticle fluctuates more and more, but the form of the function θ(b) remains essentially unchanged [8

Scanning probe microscopy and related methods

• Ernst Meyer

Beilstein J. Nanotechnol. 2010, 1, 155–157, doi:10.3762/bjnano.1.18

• molecules on surfaces. AFM has evolved considerably in the last few years, where new operation modes, such as non-contact force microscopy (nc-AFM), Kelvin probe force microscopy (KPFM) or friction force microscopy (FFM), were developed. One main focus is the high resolution capabilities of nc-AFM, which