Molecular dynamics simulations of mechanical failure in polymorphic arrangements of amyloid fibrils containing structural defects

• Hlengisizwe Ndlovu,
• Alison E. Ashcroft,
• Sheena E. Radford and
• Sarah A. Harris

Beilstein J. Nanotechnol. 2013, 4, 429–440, doi:10.3762/bjnano.4.50

• simulation were used to ensure that the trajectories sampled different areas of phase space. The SMD simulations all used a spring constant of 500 pN/Å with a constant pulling velocity of 0.01 Å/ps unless otherwise stated. The duration of the SMD simulations were 4 ns for “stretch”, “slide” and “shear

Optimal geometry for a quartz multipurpose SPM sensor

• Julian Stirling

Beilstein J. Nanotechnol. 2013, 4, 370–376, doi:10.3762/bjnano.4.43

• excited at or near one of its eigenfrequencies, properties such as the Q factor, eigenfrequencies, effective spring constant [1] and other geometrical properties [2] of the eigenmodes become important. AFM and LFM sensors have evolved from gold foil with diamond tip [3] and bent tungsten wires [4

• atomic-resolution imaging the effective spring constant of the excited eigenmode should be low [13]. However, as the spring constant normal to the surface lowers, the risk of the probe snapping to contact with the surface increases. This produces a problem for combined AFM/LFM using the principal and

• first torsional eigenmode of a cantilever, as the torsional mode can have an effective spring constant of up to approximately two orders of magnitude higher than the principal mode [10]. This results in a difficult tradeoff. To avoid snap to contact, the following condition must be satisfied [14]: where

Polynomial force approximations and multifrequency atomic force microscopy

• Daniel Platz,
• Daniel Forchheimer,
• Erik A. Tholén and
• David B. Haviland

Beilstein J. Nanotechnol. 2013, 4, 352–360, doi:10.3762/bjnano.4.41

• drive force and a time-dependent tip–surface force where the dot denotes differentiation with respect to time, ω0, Q and kc are the mode’s resonance frequency, quality factor and spring constant respectively, and h is the static equilibrium position of the tip above the surface. One should note that the

• cantilever (Bruker MPP-11120) was calibrated by a noninvasive thermal method [30] and had a resonance frequency of f0 = 229.802 kHz, a quality factor of Q = 396.9 and a spring constant of kc = 16.0 N m−1. The slow surface approach velocity was 2 nm s−1. PS (Mw = 280 kDa, Sigma-Aldrich) and PMMA (Mw = 120 kDa

• , Sigma-Aldrich) were spin-cast from toluene solution with a concentration of 0.53 %wt at a ratio of 3:1 (PMMA:PS). The sample was scanned in a Bruker Multimode 2 AFM system with a cantilever BS 300Al-G (Budget Sensors) having a resonance frequency f0 = 343.379 kHz, quality factor Q = 556.9 and spring

High-resolution nanomechanical analysis of suspended electrospun silk fibers with the torsional harmonic atomic force microscope

• Mark Cronin-Golomb and
• Ozgur Sahin

Beilstein J. Nanotechnol. 2013, 4, 243–248, doi:10.3762/bjnano.4.25

• measuring the quasi-static force from vertical deflections while monitoring the torsional deflection signal. Note that the same force acts on both vertical and torsional modes. Therefore, after calibrating the vertical spring constant, the gain of the torsional mode can be determined by comparing time

• various physical models to obtain parameters describing the mechanical response of the sample. In the case of electrospun silk fibers, we have calculated both the local elastic modulus and the local spring constant values. The elastic modulus is calculated according to the Derjaguin–Muller–Toporov (DMT

• ) model and the spring constant (stiffness) is calculated by fitting the unloading portion of the force–distance curve with a straight line. For the DMT model, we used a tip radius of 7 nm, which is characterized by blind reconstruction from a sample with sharp edges. Our calculations assumed that the

Selective surface modification of lithographic silicon oxide nanostructures by organofunctional silanes

• Thomas Baumgärtel,
• Christian von Borczyskowski and
• Harald Graaf

Beilstein J. Nanotechnol. 2013, 4, 218–226, doi:10.3762/bjnano.4.22

• ethanol followed by drying in a nitrogen stream. LAO experiments as well as topography measurements were conducted with an Anfatec Level AFM (Anfatec Instruments AG, Germany) by using platinum-coated silicon tips (”NSC18/Pt”, resonance frequency 75 Hz, spring constant 3.5 N/m, Mikromash, Estonia). As the

Calculation of the effect of tip geometry on noncontact atomic force microscopy using a qPlus sensor

• Julian Stirling and
• Gordon A. Shaw

Beilstein J. Nanotechnol. 2013, 4, 10–19, doi:10.3762/bjnano.4.2

• has a tip comparable in length to the tine [10]. Hence, the macroscopic geometry of the tip also cannot be ignored [11]. The spring constant of the sensor must be known for any conversion from raw data to meaningful force measurements [12]. However, despite the quoted piconewton precision of qPlus

• measurements [3], the spring constant is often left unmeasured and is assumed to be k ≈ 1800 N·m−1 from the geometry of the bare tine [10]. Measurements of the spring constants of qPlus sensors have produced conflicting results [4][13], which highlights the need for more detailed analysis. Tung et al. [11

• for the deflection, elastic potential energy, and spring constant of the tine of a qPlus sensor, for an arbitrary tip geometry. Furthermore, we derive the resulting lateral component of the motion of the tip apex, showing it, both theoretically and experimentally, to be comparable to the amplitude of

Characterization of the mechanical properties of qPlus sensors

• Jan Berger,
• Martin Švec,
• Martin Müller,
• Martin Ledinský,
• Antonín Fejfar,
• Pavel Jelínek and
• Zsolt Majzik

Beilstein J. Nanotechnol. 2013, 4, 1–9, doi:10.3762/bjnano.4.1

• microscope utilized in this work has a resolution of about 2 μm, from this we estimate an error of the length measurement less than 1% and for the diameter of ≈8%. Consequently, the estimation of the added mass has a maximal error of about 11%. Because the spring constant depends on the added mass linearly

• vibration). This method is the only one mentioned in this paper that is able to estimate the spring constant during the course of an UHV AFM experiment. Generally, UHV AFM/STM instruments are able to reach a high level of vibrational isolation, which is needed to minimize extra mechanical excitation from

Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

• Baran Eren,
• Dorothée Hug,
• Laurent Marot,
• Rémy Pawlak,
• Marcin Kisiel,
• Roland Steiner,
• Dominik M. Zumbühl and
• Ernst Meyer

Beilstein J. Nanotechnol. 2012, 3, 852–859, doi:10.3762/bjnano.3.96

• fundamental frequency, spring constant, and quality factor of the cantilever were equal to f0 = 142 kHz, k = 20 N/m, Q = 300, respectively. We avoided performing electron microscopy on the HOPG samples because the electron beam energy could ionize H2O and NH3 adsorbents and cause additional effects [43]. XPS

Spring constant of a tuning-fork sensor for dynamic force microscopy

• Dennis van Vörden,
• Manfred Lange,
• Merlin Schmuck,
• Nico Schmidt and
• Rolf Möller

Beilstein J. Nanotechnol. 2012, 3, 809–816, doi:10.3762/bjnano.3.90

• Dennis van Vorden Manfred Lange Merlin Schmuck Nico Schmidt Rolf Moller Faculty of Physics, University of Duisburg-Essen, Lotharstr. 1–21 47048 Duisburg, Germany 10.3762/bjnano.3.90 Abstract We present an overview of experimental and numerical methods to determine the spring constant of a quartz

• taking account of the real geometry including the glue that is used to mount the tuning fork. Keywords: atomic force microscopy; finite element method; spring constant; thermal fluctuation; tuning fork; Introduction Quartz tuning forks provide excellent self-sensing probes in scanning probe microscopy

• and sample surface, according to where is the average force gradient between tip and sample, Δf is the frequency shift, k is the spring constant of the sensor and f0 is the resonance frequency of the sensor without interaction with the sample. While the resonance frequency may be measured accurately

Growth behaviour and mechanical properties of PLL/HA multilayer films studied by AFM

• Cagri Üzüm,
• Johannes Hellwig,
• Narayanan Madaboosi,
• Dmitry Volodkin and
• Regine von Klitzing

Beilstein J. Nanotechnol. 2012, 3, 778–788, doi:10.3762/bjnano.3.87

• . The full-indentation method requires a stiff, calibrated cantilever equipped with a tip that is significantly longer than the film is thick. The measurements are reasonably fast and reproducible, and the film damage caused is limited to a small area (r ≈ 50 nm). The spring constant of the cantilever

• rigid surface and driving it further down by the piezo unit for a known distance. As there could not be any indentation on a hard surface, the driving distance was equal to the deflection of the cantilever. This step is crucial both for determination of the spring constant and for indentation

• measurements. Although the spring constant kc was given by the manufacturer as 0.05 N/m (unless stated otherwise), its exact value was determined before each measurement by the thermal noise method, which is a built-in procedure in the MFP-3D instrument (Asylum Research, CA, USA). Thickness measurements Two

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

• mode, in which the deflection sensitivity obtained from the force curve was multiplied by the change in setpoint voltage. For single-nanoparticle contact, a sharp silicon tip (FORT series, Applied NanoStructures, Inc., Santa Clara, CA,) with a spring constant k = 3 N/m and nominal radius of 15 nm was

• of friction, a soda lime glass sphere (Duke Scientific Corporation, Palo Alto, CA) of nominal radius 15 µm attached to a silicon probe (FORT series, Applied NanoStructures, Inc., Santa Clara, CA,) with a spring constant k = 3 N/m was used. Coefficient of friction data were obtained by plotting the

Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing

• Blake W. Erickson,
• Séverine Coquoz,
• Jonathan D. Adams,
• Daniel J. Burns and
• Georg E. Fantner

Beilstein J. Nanotechnol. 2012, 3, 747–758, doi:10.3762/bjnano.3.84

• . Quantitative Nanomechanical Mapping (QNM) – AFM imaging in fluid Images were captured on a Multimode system with an E-scanner (Bruker Nano: Santa Barbara, CA, USA). A standard DNP-A (Bruker AFM Probes: Camarillo, CA, USA) cantilever was used with a spring constant of 0.40 N/m. Images at 5 µm were captured at

• modified Multimode system with an E-scanner (Bruker Nano: Santa Barbara, CA, USA). A customized small-lever head allowed for the use of small cantilevers (SCL-Sensor.Tech., Vienna, Austria). The cantilever had a resonance frequency in fluid of 266.49 kHz, a spring constant of 0.54 N/m and a Q value of 2.68

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

• Nanoscale surface roughness and coefficient of friction were measured by using a commercial AFM system (Dimension Nanoscope IIIa, Veeco, Santa Barbara, CA) under ambient conditions. Fort A-20 tips (Si, N-type, 10 nm radius, spring constant of 3 N/m) (Appnano, Santa Clara, CA) were used. The coefficient of

Mapping mechanical properties of organic thin films by force-modulation microscopy in aqueous media

• Jianming Zhang,
• Zehra Parlak,
• Carleen M. Bowers,
• Terrence Oas and
• Stefan Zauscher

Beilstein J. Nanotechnol. 2012, 3, 464–474, doi:10.3762/bjnano.3.53

• angular frequency of the actuation, kc is the spring constant of the AFM cantilever, and k* is the contact stiffness, The contact stiffness is a function of the reduced Young’s modulus, E*, the tip radius, R, and the applied force, F. Equation 1 explains how the amplitude of the AFM cantilever deflection

• a gold surface, are shown in Figure 2. For these experiments, we used a cantilever with a spring constant of 0.9 N/m and a resonance frequency of 47.8 kHz in solution. The different regions of the deflection (Figure 2a) and amplitude curves (Figure 2b and Figure 2d) indicate both the position of the

• be soft to prevent destructive forces on compliant samples. Therefore we used ScanAsyst-Fluid cantilevers (Bruker Probes) that have 0.7 N/m nominal spring constant and 50 kHz free resonance frequency in solution. The deflection sensitivity of each cantilever was determined from a force–displacement

Colloidal lithography for fabricating patterned polymer-brush microstructures

• Tao Chen,
• Debby P. Chang,
• Rainer Jordan and
• Stefan Zauscher

Beilstein J. Nanotechnol. 2012, 3, 397–403, doi:10.3762/bjnano.3.46

• -grade water, dried under a stream of nitrogen, and mounted on steel sample disks prior to AFM measurements. AFM topographic images were collected in contact mode by using V-shaped silicon nitride cantilevers (Nanoprobe, Veeco, spring constant 0.12 N/m; tip radius 20–60 nm) using a MultiMode atomic force

Pulse-response measurement of frequency-resolved water dynamics on a hydrophilic surface using a Q-damped atomic force microscopy cantilever

• Masami Kageshima

Beilstein J. Nanotechnol. 2012, 3, 260–266, doi:10.3762/bjnano.3.29

• held and the duty cycle of the input signal was immediately changed to 99.5% so that a square pulse with a duration of 10 μs was applied to the driver circuit. Since a soft cantilever with a nominal spring constant of 0.03 N/m was used, once it drifted into contact with the substrate during data

Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique

• Zsolt Majzik,
• Martin Setvín,
• Andreas Bettac,
• Albrecht Feltz,
• Vladimír Cháb and
• Pavel Jelínek

Beilstein J. Nanotechnol. 2012, 3, 249–259, doi:10.3762/bjnano.3.28

• the important oscillation stability [8][9][10]. The key factor to achieve atomic resolution is the proper choice of several parameters, for example, the spring constant and the oscillation amplitude (see Table I in [11]). Theoretically, the optimal signal-to-noise ratio (SNR) is achieved at a value of

Analysis of force-deconvolution methods in frequency-modulation atomic force microscopy

• Joachim Welker,
• Esther Illek and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2012, 3, 238–248, doi:10.3762/bjnano.3.27

• one oscillation cycle, which is fulfilled, for example, for small amplitudes, the actual resonance frequency f can be calculated with an effective spring constant k + kts where m is the effective mass and k the spring constant of the cantilever. For kts << k we can expand the square root in Equation 1

• (maximum attractive force). Therefore, we also compare the deviation from the model values: To calculate the frequency shift we chose a tuning fork sensor in the qPlus design [13] with a spring constant of k = 1800 N/m and a resonance frequency of f0 = 32768 Hz. This sensor can operate with very small

Modeling noncontact atomic force microscopy resolution on corrugated surfaces

• Kristen M. Burson,
• Mahito Yamamoto and
• William G. Cullen

Beilstein J. Nanotechnol. 2012, 3, 230–237, doi:10.3762/bjnano.3.26

• spring constant k = 40 N/m and resonant frequency f0 = 300 kHz. We then convert to the normalized frequency shift γ, which is defined as [20] Results and Discussion Using the model, we arrive at several key results. First, we find that the generally assumed Hamaker force law for the interaction between a

A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

• Manfred Lange,
• Dennis van Vörden and
• Rolf Möller

Beilstein J. Nanotechnol. 2012, 3, 207–212, doi:10.3762/bjnano.3.23

• to its large spring constant of about 9000 N/m. The force-spectroscopy measurements were performed on the organic molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) grown on a Ag/Si(111) √3 × √3 surface. PTCDA has been extensively studied as a candidate for organic devices [10][11][12][13

• regime due to its large spring constant of about 9000 N/m, preventing a jump to contact. This offers the advantage that in this regime the measurements are more sensitive to short-range forces and dissipation processes. The resonance frequency and quality factor of the tuning fork at 77 K temperature and

qPlus magnetic force microscopy in frequency-modulation mode with millihertz resolution

• Maximilian Schneiderbauer,
• Daniel Wastl and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2012, 3, 174–178, doi:10.3762/bjnano.3.18

• fork. The qPlus sensor [8] is based on a quartz tuning fork, in which one prong is attached to a carrier substrate. The large spring constant of the qPlus, k = 1800 Nm−1, allows one to overcome the snap-to-contact-problem in small-amplitude operation [9]. In this mode, the qPlus setup is customized for

• noise Here A is the cantilever amplitude, f0 the undisturbed resonance frequency of the cantilever, k the spring constant, Q the quality factor of the oscillation, nq the deflection-noise density, B the bandwidth of the measurement, kB the Boltzmann constant and T the temperature. In each term, the

• necessary in order to reduce the noise by reducing the bandwidth. In Figure 2b the flattened raw data of the frequency-shift channel gathered in lift-mode show an image contrast of ±5 mHz along the bit tracks. According to the resonance frequency f0 = 24097 Hz and spring constant k = 1250 Nm−1 of the sensor

Self-assembly of octadecyltrichlorosilane: Surface structures formed using different protocols of particle lithography

• ChaMarra K. Saner,
• Kathie L. Lusker,
• Zorabel M. LeJeune,
• Wilson K. Serem and
• Jayne C. Garno

Beilstein J. Nanotechnol. 2012, 3, 114–122, doi:10.3762/bjnano.3.12

• reflex coating, with a spring constant of 48 N/m (Nanoscience Instruments, Phoenix, AZ). For contact-mode images, V-shaped tips (Veeco Probes, Santa Barbara, CA) with an average force constant of 0.5 N/m were used. Data files were processed by using Gwyddion open-source software, which is freely

Electron-beam patterned self-assembled monolayers as templates for Cu electrodeposition and lift-off

• Zhe She,
• Andrea DiFalco,
• Georg Hähner and
• Manfred Buck

Beilstein J. Nanotechnol. 2012, 3, 101–113, doi:10.3762/bjnano.3.11

• structures were characterised by scanning electron microscopy (Hitachi S4800) and atomic force microscopy (PicoPlus, Molecular Imaging). Using Veeco NPS10 nonconductive silicon nitride tips (spring constant 0.06 N/m) AFM images were recorded in contact mode by using forces between 7 and 13 nN and scan rates

Direct monitoring of opto-mechanical switching of self-assembled monolayer films containing the azobenzene group

• Einat Tirosh,
• Enrico Benassi,
• Silvio Pipolo,
• Marcel Mayor,
• Michal Valášek,
• Veronica Frydman,
• Stefano Corni and
• Sidney R. Cohen

Beilstein J. Nanotechnol. 2011, 2, 834–844, doi:10.3762/bjnano.2.93

• measurement, Au and glass are considered equally stiff since the modulus signal saturates at about 5 GPa due to the limits of the cantilever spring constant and the signal sensitivities. The glass surface then serves as an in situ reference to which the film modulus can be compared. Scanning these samples

Manipulation of gold colloidal nanoparticles with atomic force microscopy in dynamic mode: influence of particle–substrate chemistry and morphology, and of operating conditions

• Samer Darwich,
• Karine Mougin,
• Akshata Rao,
• Enrico Gnecco,
• Shrisudersan Jayaraman and
• Hamidou Haidara

Beilstein J. Nanotechnol. 2011, 2, 85–98, doi:10.3762/bjnano.2.10

• amplitude of a piezo-element coupled to the cantilever, f0, k and Q are the resonance frequency, the spring constant and the quality factor of the free cantilever, respectively, and is the phase shift caused by the interaction between the tip and the underlying particles or surface. The calculation of the