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

• testing different scenarios, LDP results have shown the significant influence of the stiffness gradient in the robustness of the adhesion and the adaptability of the contact. Parness et al. [23] fabricated one of the first synthetic structures which performed similar to a gecko. While their adhesion was

• compliance and facilitates the use of such a stiff polymer. The joint stiffness was controlled using three polyurethane materials of elastic moduli Ej = 0.45, 8.89 and 126 MPa as the joint material. The final array of the composite fibers consisted of a stiff stalk and tip linked by a soft joint as shown in

• . Let us model the flexible joint as a torsional spring of stiffness added to the end of the fiber, where Ej is the elastic modulus of the joint material and f is the thickness of the joint in terms of overall effective length L of the fiber, and I is the area moment of inertia of the fiber assuming

Effective sensor properties and sensitivity considerations of a dynamic co-resonantly coupled cantilever sensor

• Julia Körner

Beilstein J. Nanotechnol. 2018, 9, 2546–2560, doi:10.3762/bjnano.9.237

• maintaining the ease of detection. Experimentally, a low-stiffness nanocantilever is coupled to an easy to read out microcantilever and the eigenfrequencies of both beams are brought close to one another. This results in a strong interplay between both beams and, hence, any interaction applied at the

• cantilever mass. Another approach of reaching femtonewton force sensitivity has been demonstrated for optomechanical cantilever sensors by optimizing cantilever design for high quality factors (in the order of 106). Consequently, cantilevers with rather high stiffness (kN/m) can be used, avoiding the snap-to

• stiffness of the nanocantilever and room temperature were assumed. A decrease in stiffness, especially of the nanocantilever, and low temperatures will lead to much more gain in sensitivity. With the derived expressions within this work, a fast and easy way to estimate the potential sensitivity is given

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

• graded materials; numerical simulations; Introduction Materials with a gradient in their physical or elastic properties are widely found in nature. Several known biological systems have developed specialized functionalities due to stiffness, density or composition gradients. Beetles, for instance

• , display setae with a graded stiffness that optimises the adhesive performance on rough surfaces [1]. Hardness and stiffness gradients are of fundamental importance in the biomechanics of contacts, since they allow increased resistance against wear, impact, penetration and crack propagation [2][3][4][5][6

• stiffness of the springs along the axis is set to Kint = 3/4 Elz, and of the diagonal springs to Kint/2 [37]. Thus, the internal elastic force exerted on the generic block i by its neighbour j is Fint(ij) = kij (rij − lji) (rj − ri) /rij, where ri and rj are the position vectors of blocks i and j

Magnetism and magnetoresistance of single Ni–Cu alloy nanowires

• Andreea Costas,
• Camelia Florica,
• Elena Matei,
• Maria Eugenia Toimil-Molares,
• Ionel Stavarache,
• Andrei Kuncser,
• Victor Kuncser and
• Ionut Enculescu

Beilstein J. Nanotechnol. 2018, 9, 2345–2355, doi:10.3762/bjnano.9.219

• also related to an exchange length parameter, λex = π√(A/K), where A is the exchange stiffness and K is the anisotropy constant, respectively. Even for single-component metallic nanowires (e.g., Ni) of high aspect ratio, different magnetization reversal mechanisms might be in work (from the simplest

• gradient method were performed for all points obtained on the hysteresis plot. In addition to the abovementioned geometrical aspects, the simulations require also two additional magnetic parameters: (i) the spontaneous magnetization (well approximated by the saturation magnetization) and (ii) the stiffness

• [27]. However, the above estimations allowed us to perform micromagnetic simulations on similar cylindrical magnetic structures of high aspect ratio with saturation magnetizations of about 105 A·m−1 and stiffness constants of about 10−22 J·m−1 (as specific to Ni and Ni alloys) [31][32]. The

Fabrication of photothermally active poly(vinyl alcohol) films with gold nanostars for antibacterial applications

• Mykola Borzenkov,
• Maria Moros,
• Claudia Tortiglione,
• Serena Bertoldi,
• Nicola Contessi,
• Silvia Faré,
• Angelo Taglietti,
• Agnese D’Agostino,
• Piersandro Pallavicini,
• Maddalena Collini and
• Giuseppe Chirico

Beilstein J. Nanotechnol. 2018, 9, 2040–2048, doi:10.3762/bjnano.9.193

• stress–strain curves of the three types of films followed the same trend, however being characterized by different elastic modulus, maximum stress and maximum strain values. In particular, PVA films without GNSs showed the lowest stiffness value in comparison with both types of PVA-GNS films (p < 0.05

Recent highlights in nanoscale and mesoscale friction

• Andrea Vanossi,
• Dirk Dietzel,
• Andre Schirmeisen,
• Ernst Meyer,
• Rémy Pawlak,
• Thilo Glatzel,
• Marcin Kisiel,
• Shigeki Kawai and
• Nicola Manini

Beilstein J. Nanotechnol. 2018, 9, 1995–2014, doi:10.3762/bjnano.9.190

Preparation of micro/nanopatterned gelatins crosslinked with genipin for biocompatible dental implants

• Reika Makita,
• Tsukasa Akasaka,
• Seiichi Tamagawa,
• Yasuhiro Yoshida,
• Saori Miyata,
• Hirofumi Miyaji and
• Tsutomu Sugaya

Beilstein J. Nanotechnol. 2018, 9, 1735–1754, doi:10.3762/bjnano.9.165

• of vinculin spots on pillars with heights of 2 µm after 7 days of culturing appeared weaker than the strength after 1 day of culturing. The difference in distribution or strength of vinculin spots may be caused by substrate stiffness [63]. These data support the concept that patterning of gelatin

Electrostatically actuated encased cantilevers

• Benoit X. E. Desbiolles,
• Gabriela Furlan,
• Adam M. Schwartzberg,
• Paul D. Ashby and
• Dominik Ziegler

Beilstein J. Nanotechnol. 2018, 9, 1381–1389, doi:10.3762/bjnano.9.130

• immersed in a viscous fluid. Quantitative measurements of stiffness, energy dissipation and tip–sample interactions using dynamic force sensors remain challenging due to spurious resonances of the system. Results: We demonstrate for the first time electrostatic actuation with a built-in electrode. Solely

• ≈ 90 μm) with a stiffness of k = 4 N·m−1 and a resonance frequency of f0 = 144.525 kHz and Qair = 36.5 is used. After immersion in water the quality factor remained high Qwater = 27.4, which enables high-resolution imaging with small interaction forces in liquids. Moreover, the clean electrostatic

• , the well-known expression for deflection of a uniformly loaded cantilever can be used. y(l) = ql4/(8EI). Inserting the static stiffness kstat = 3EI/l3 and q = Fdc/l we can express y(l) as a function of the capacitance gradient (C′), stiffness (kstat) and electrical potentials (Udc, UCPD, and Uac): To

Atomistic modeling of tribological properties of Pd and Al nanoparticles on a graphene surface

• Alexei Khomenko,
• Miroslav Zakharov,
• Denis Boyko and
• Bo N. J. Persson

Beilstein J. Nanotechnol. 2018, 9, 1239–1246, doi:10.3762/bjnano.9.115

• different temperatures, and showed how the static friction and contact stiffness depend on the contact area. They observed “contact aging” due to stress-aided, thermally activated atomic rearrangement processes. The term “contact aging” [6] is related to time-dependent atomic reconstructions at the

Electrostatic force spectroscopy revealing the degree of reduction of individual graphene oxide sheets

• Yue Shen,
• Ying Wang,
• Yuan Zhou,
• Chunxi Hai,
• Jun Hu and
• Yi Zhang

Beilstein J. Nanotechnol. 2018, 9, 1146–1155, doi:10.3762/bjnano.9.106

• force gradients cause shifts of Δf0 in the resonance frequency with a proportional relationship [30]: where k is the stiffness (or spring constant) of the cantilever. Resonance shifts also give rise to phase shifts, ∆φ, used to generate an image of the electric force gradients. In EFM imaging, the

Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

• Anulekha De,
• Sucheta Mondal,
• Sourav Sahoo,
• Saswati Barman,
• Yoshichika Otani,
• Rajib Kumar Mitra and
• Anjan Barman

Beilstein J. Nanotechnol. 2018, 9, 1123–1134, doi:10.3762/bjnano.9.104

• Oe−1, anisotropy field Hk = 0, saturation magnetization Ms = 860 emu cm−3, and exchange stiffness constant A = 1.3 × 10−6 erg cm−1. The material parameters were extracted by measuring the variation of precessional frequency (f) with bias magnetic field H for a Py thin film and by fitting them using

• Kittel formula, The exchange stiffness constant A is obtained from literature [39]. A pulsed field of peak value of 30 Oe, 10 ps rise/fall time and 20 ps pulse duration is used perpendicular to the sample plane, while a damping coefficient α = 0.008 is used during dynamic simulations. The experimentally

Imaging of viscoelastic soft matter with small indentation using higher eigenmodes in single-eigenmode amplitude-modulation atomic force microscopy

• Miead Nikfarjam,
• Enrique A. López-Guerra,
• Santiago D. Solares and
• Babak Eslami

Beilstein J. Nanotechnol. 2018, 9, 1116–1122, doi:10.3762/bjnano.9.103

• the first three flexural eigenmodes, using an individual equation of motion for each of them, all coupled through the tip–sample forces: Here zi, ki, Qi and refer to the i-th (with i = 1, 2, 3) eigenmode displacement, cantilever stiffness, cantilever quality factor, and resonance frequency

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

• Jaison Jeevanandam,
• Ahmed Barhoum,
• Yen S. Chan,
• Alain Dufresne and
• Michael K. Danquah

Beilstein J. Nanotechnol. 2018, 9, 1050–1074, doi:10.3762/bjnano.9.98

• stiffness, and as transparent layers used for heated, mist and ice-free, window panes [35]. By the end of 2003, Mercedes-Benz brought a NP-based clear coat into series production for both metallic and nonmetallic paint finishes. The coating increases the scratch resistance and enhances the gloss. Liquid

• nanocomposite. Nacre is designed by alternating micrometer-sized and sub-micrometer CaCO3 aragonite platelets, which are separated by a thin layer of bio-macromolecular “glue”. Enhanced stiffness, impact resistance, strength, and toughness are some of the mechanical properties that enable using nacre’s unique

Automated image segmentation-assisted flattening of atomic force microscopy images

• Yuliang Wang,
• Tongda Lu,
• Xiaolai Li and
• Huimin Wang

Beilstein J. Nanotechnol. 2018, 9, 975–985, doi:10.3762/bjnano.9.91

• AFM (Resolve, Bruker) in tapping mode with 96% setpoint value. A silicon cantilever (NSC36/ALBS, MikroMasch) with quoted stiffness of 0.6 N/m and tip radius of 8 nm was used for scanning. The scanning frequency and scanning angle were 2 Hz and 0°, respectively. Methods The step-by-step procedure of

Scanning speed phenomenon in contact-resonance atomic force microscopy

• Christopher C. Glover,
• Jason P. Killgore and
• Ryan C. Tung

Beilstein J. Nanotechnol. 2018, 9, 945–952, doi:10.3762/bjnano.9.87

• hydrophilic sample to show that hydrodynamic stiffness of an adsorbed water layer is a plausible explanation for scan speed-induced changes in the mechanical coupling of tip and sample. Theory In air, a native adsorbed layer of water exists on all surfaces. This layer, in some cases, is several nanometers

• stiffness is now a series combination of the fluid film stiffness kf and the material stiffness ks. There may also be additional damping effects introduced by the fluid film, which we would like to address in future research studies. For instance, it is known that the modulation of the tip–sample contact

• approximately as Vs/h3 for a simple two-dimensional slider model [20], where Vs is the velocity of the slider and h is the fluid gap height. Using this simple model, the hydrodynamic stiffness kf, which is proportional to ∂F/∂h (), varies approximately as Vs/h4. A very small fluid film layer can provide a very

Effect of microtrichia on the interlocking mechanism in the Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae)

• Jiyu Sun,
• Chao Liu,
• Bharat Bhushan,
• Wei Wu and
• Jin Tong

Beilstein J. Nanotechnol. 2018, 9, 812–823, doi:10.3762/bjnano.9.75

• friction force of the DS–DS and VS–VS interactions is greater than that of the interaction between the VS and the abdomen. An additional explanation is that the vein is like a spring-loaded tape measure (that is, a carpenter’s tape) that can stabilize in the unfolded shape and confer sufficient stiffness

Lyapunov estimation for high-speed demodulation in multifrequency atomic force microscopy

• David M. Harcombe,
• Michael G. Ruppert,
• Michael R. P. Ragazzon and
• Andrew J. Fleming

Beilstein J. Nanotechnol. 2018, 9, 490–498, doi:10.3762/bjnano.9.47

• stiffness, elasticity and adhesiveness [10]. The acquisition of these observables requires tracking the amplitude and phase of additional frequencies of interest. These include higher harmonics of the fundamental frequency [11], higher flexural eigenmodes [12] and intermodulation products [13]. Higher

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

• Liga Jasulaneca,
• Jelena Kosmaca,
• Raimonds Meija,
• Jana Andzane and
• Donats Erts

Beilstein J. Nanotechnol. 2018, 9, 271–300, doi:10.3762/bjnano.9.29

• , initiation of a current flow in the circuit (Figure 1b,d; Figure 2b) [13][15][32][40][68]. The jump-in voltage depends on the geometry of the device and the stiffness of the switching element. Switching from the on to off state (jump-off) occurs when the spring constant of the switching element exceeds the

• restoring force to the switching element in the 3T configuration reduces the requirements to elastic properties (stiffness) of the active element necessary for switching to the off position and allows reducing the jump-in voltage by diminishing the separation gap width. However, the gap cannot be smaller

• ] (Table 1). Thus, the contact area experiences higher current density than that inside the nanowire. This should be taken into account during analysis performed on NEM switch operation. The nanocontact area and stiffness of the switching element determine the on–off hysteresis width of a NEM switch. With

Anchoring of a dye precursor on NiO(001) studied by non-contact atomic force microscopy

• Sara Freund,
• Antoine Hinaut,
• Nathalie Marinakis,
• Edwin C. Constable,
• Ernst Meyer,
• Catherine E. Housecroft and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2018, 9, 242–249, doi:10.3762/bjnano.9.26

• ), using silicon cantilever (Nanosensors PPP-NCR, stiffness k = 20–30 N/m, resonance frequency f1 around 165 kHz, Qf1 factor around 30000, torsional frequency fTR around 1.5 MHz, and QTR factors around 100000) with compensated contact potential difference (CPD). Kelvin probe force microscopy was performed

Liquid-crystalline nanoarchitectures for tissue engineering

• Baeckkyoung Sung and
• Min-Ho Kim

Beilstein J. Nanotechnol. 2018, 9, 205–215, doi:10.3762/bjnano.9.22

• shown to result in enhanced cellular reorganization and facilitated tissue morphogenesis [55]. Mechanical stiffness of tissues is an important physical cue for modulating the behavior of adhered or embedded cells [56][57]. The LC architectures of ECM fibers may influence the functionality of target

• tissue by altering the elastic modulus of tissue [58]. Hard tissues Skeletal tissues are mineralized compact matrices of ordered biopolymers [59]. In vertebrates, bones consist of a dense mesophase of collagen fibrils [60], which has been believed to render mechanical stiffness to the skeletal tissues

• exhibited a high stiffness (570 kPa of Young’s modulus). Optical transparency of the dense collagen film in the visible spectral range could be maintained after formation of an epithelium of human corneal epithelial cells in vitro [87]. The cornea-like 3D plywood cholesteric organization of the collagen

Humidity-dependent wound sealing in succulent leaves of Delosperma cooperi – An adaptation to seasonal drought stress

• Olga Speck,
• Mark Schlechtendahl,
• Florian Borm,
• Tim Kampowski and
• Thomas Speck

Beilstein J. Nanotechnol. 2018, 9, 175–186, doi:10.3762/bjnano.9.20

• -sectional area (). The strain (ε) was calculated (Equation 4) as the fraction of the displacement (ΔL) divided by the original length (L0) of a tested sample. The elastic modulus, a measure of material stiffness, was calculated (Equation 5) from the slope of the initial (in good approximation) linear (i.e

A robust AFM-based method for locally measuring the elasticity of samples

• Alexandre Bubendorf,
• Stefan Walheim,
• Thomas Schimmel and
• Ernst Meyer

Beilstein J. Nanotechnol. 2018, 9, 1–10, doi:10.3762/bjnano.9.1

• [7]. In Hurley and Turner’s [6] method, the stated equations for the computation of the normal sample stiffness by numerical methods (analytical expression for normal sample stiffness formulated by Bubendorf [8] and given in Supporting Information File 1) used to determine sample elasticity are based

• . Analysis of the force–displacement curve evidences the same relations with, however, a linear relation in the nonlinear domain of the frequency shift–displacement curves. This is explained by the low spring constant of the cantilever in comparison to the normal sample stiffness, beginning at a certain Z

• -displacement value. A good model of the cantilever in contact with the sample surface is two springs in series, k1 and ksample,norm, representing the spring constant of the cantilever and the normal sample stiffness (of constant value in the elastic phase), respectively (Figure 4a). As shown in Figure 4b, the

Material discrimination and mixture ratio estimation in nanocomposites via harmonic atomic force microscopy

• Weijie Zhang,
• Yuhang Chen,
• Xicheng Xia and
• Jiaru Chu

Beilstein J. Nanotechnol. 2017, 8, 2771–2780, doi:10.3762/bjnano.8.276

• cantilever deflection. Fn = knAn/Qn is the drive force. kn, An, Qn and ωn are the equivalent cantilever stiffness, amplitude, quality factor and angular resonance frequency, respectively. The interaction forces Fts, depend on the instantaneous gap, d, and they are simplified as, Here the attractive forces

• frequencies [33][34]. A higher elastic modulus, and therefore higher stiffness, will lead to a larger frequency shift, as schematically illustrated by the solid line, see Figure 4b. Similarly, a smaller elastic modulus causes a smaller frequency shift, as depicted by the dotted line. When the drive frequency

Exploring wear at the nanoscale with circular mode atomic force microscopy

• Olivier Noel,
• Aleksandar Vencl and
• Pierre-Emmanuel Mazeran

Beilstein J. Nanotechnol. 2017, 8, 2662–2668, doi:10.3762/bjnano.8.266

• range of cantilever stiffness. Experimental images as shown in Figure 3C and in Figure 4 also show that the material is not uniformly worn along the circular wear track. Wear is more intensive at some random locations of the material, evidencing heterogeneous wear (as in Figure 3C) or production of wear

• stiffness was 12 N/m and 0.4 N/m, respectively (as determined by the thermal noise method [27][28]). For each set of wear experiments, a unique AFM tip was used. After each measurement, force curves on a silicon wafer were performed to verify the state of the tip. Every data point represented in Figure 5

Robust nanobubble and nanodroplet segmentation in atomic force microscope images using the spherical Hough transform

• Yuliang Wang,
• Tongda Lu,
• Xiaolai Li,
• Shuai Ren and
• Shusheng Bi

Beilstein J. Nanotechnol. 2017, 8, 2572–2582, doi:10.3762/bjnano.8.257

• both air and DI water using a commercial AFM (Resolve, Bruker) in tapping mode with 96% setpoint value. Silicon cantilevers (NSC36/ALBS, MikroMasch) with a quoted stiffness of 0.6 N/m and tip radius of 8 nm were used for scanning. The measured resonance frequencies of the cantilever were 55 kHz and 16