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Cafolla C, Voïtchovsky K, Payam AF. Simultaneous quantification of Young's modulus and dispersion forces with nanoscale spatial resolution. NANOTECHNOLOGY 2023; 34:505714. [PMID: 37699380 DOI: 10.1088/1361-6528/acf8ce] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/11/2023] [Indexed: 09/14/2023]
Abstract
Many advances in polymers and layered materials rely on a precise understanding of the local interactions between adjacent molecular or atomic layers. Quantifying dispersion forces at the nanoscale is particularly challenging with existing methods often time consuming, destructive, relying on surface averaging or requiring bespoke equipment. Here, we present a non-invasive method able to quantify the local mechanical and dispersion properties of a given sample with nanometer lateral precision. The method, based on atomic force microscopy (AFM), uses the frequency shift of a vibrating AFM cantilever in combination with established contact mechanics models to simultaneously derive the Hamaker constant and the effective Young's modulus at a given sample location. The derived Hamaker constant and Young's modulus represent an average over a small (typically <100) number of molecules or atoms. The oscillation amplitude of the vibrating AFM probe is used to select the length-scale of the features to analyse, with small vibrations able to resolve the contribution of sub-nanometric defects and large ones exploring effectively homogeneous areas. The accuracy of the method is validated on a range of 2D materials in air and water as well as on polymer thin films. We also provide the first experimental measurements of the Hamaker constant of HBN, MoT2, WSe2and polymer films, verifying theoretical predictions and computer simulations. The simplicity and robustness of the method, implemented with a commercial AFM, may support a broad range of technological applications in the growing field of polymers and nanostructured materials where a fine control of the van der Waals interactions is crucial to tune their properties.
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Affiliation(s)
- Clodomiro Cafolla
- Physics Department, Durham University, Durham, DH1 3LE, United Kingdom
| | | | - Amir Farokh Payam
- Nanotechnology and Integrated Bioengineering Centre (NIBEC), School of Engineering, Ulster University, United Kingdom
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Almonte L, Colchero J. True non-contact atomic force microscopy imaging of heterogeneous biological samples in liquids: topography and material contrast. NANOSCALE 2017; 9:2903-2915. [PMID: 28181615 DOI: 10.1039/c6nr07967a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The present work analyses how the tip-sample interaction signals critically determine the operation of an Atomic Force Microscope (AFM) set-up immersed in liquid. On heterogeneous samples, the conservative tip-sample interaction may vary significantly from point to point - in particular from attractive to repulsive - rendering correct feedback very challenging. Lipid membranes prepared on a mica substrate are analyzed as reference samples which are locally heterogeneous (material contrast). The AFM set-up is operated dynamically at low oscillation amplitude and all available experimental data signals - the normal force, as well as the amplitude and frequency - are recorded simultaneously. From the analysis of how the dissipation (oscillation amplitude) and the conservative interaction (normal force and resonance frequency) vary with the tip-sample distance we conclude that dissipation is the only appropriate feedback source for stable and correct topographic imaging. The normal force and phase then carry information about the sample composition ("chemical contrast"). Dynamic AFM allows imaging in a non-contact regime where essentially no forces are applied, rendering dynamic AFM a truly non-invasive technique.
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Affiliation(s)
- Lisa Almonte
- Centro de Investigación en Óptica y Nanofísica (CIOyN), Departamento Física, Facultad de Química (Campus Espinardo), Universidad de Murcia, E-30100 Murcia, Spain.
| | - Jaime Colchero
- Centro de Investigación en Óptica y Nanofísica (CIOyN), Departamento Física, Facultad de Química (Campus Espinardo), Universidad de Murcia, E-30100 Murcia, Spain.
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Dynamic modeling and sensitivity analysis of dAFM in the transient and steady state motions. Ultramicroscopy 2016; 169:55-61. [DOI: 10.1016/j.ultramic.2016.05.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/20/2016] [Accepted: 05/26/2016] [Indexed: 11/23/2022]
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Ares P, Fuentes-Perez ME, Herrero-Galán E, Valpuesta JM, Gil A, Gomez-Herrero J, Moreno-Herrero F. High resolution atomic force microscopy of double-stranded RNA. NANOSCALE 2016; 8:11818-11826. [PMID: 26876486 DOI: 10.1039/c5nr07445b] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Double-stranded (ds) RNA mediates the suppression of specific gene expression, it is the genetic material of a number of viruses, and a key activator of the innate immune response against viral infections. The ever increasing list of roles played by dsRNA in the cell and its potential biotechnological applications over the last decade has raised an interest for the characterization of its mechanical properties and structure, and that includes approaches using Atomic Force Microscopy (AFM) and other single-molecule techniques. Recent reports have resolved the structure of dsDNA with AFM at unprecedented resolution. However, an equivalent study with dsRNA is still lacking. Here, we have visualized the double helix of dsRNA under near-physiological conditions and at sufficient resolution to resolve the A-form sub-helical pitch periodicity. We have employed different high-sensitive force-detection methods and obtained images with similar spatial resolution. Therefore, we show here that the limiting factors for high-resolution AFM imaging of soft materials in liquid medium are, rather than the imaging mode, the force between the tip and the sample and the sharpness of the tip apex.
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Affiliation(s)
- Pablo Ares
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, E-28049 Madrid, Spain.
| | - Maria Eugenia Fuentes-Perez
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco, Madrid, Spain.
| | - Elías Herrero-Galán
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco, Madrid, Spain.
| | - José M Valpuesta
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco, Madrid, Spain.
| | - Adriana Gil
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco, Madrid, Spain.
| | - Julio Gomez-Herrero
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, E-28049 Madrid, Spain. and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049, Madrid, Spain
| | - Fernando Moreno-Herrero
- Department of Macromolecular Structures, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, 28049 Cantoblanco, Madrid, Spain.
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Payam AF, Martin-Jimenez D, Garcia R. Force reconstruction from tapping mode force microscopy experiments. NANOTECHNOLOGY 2015; 26:185706. [PMID: 25876817 DOI: 10.1088/0957-4484/26/18/185706] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Fast, accurate, and robust nanomechanical measurements are intensely studied in materials science, applied physics, and molecular biology. Amplitude modulation force microscopy (tapping mode) is the most established nanoscale characterization technique of surfaces for air and liquid environments. However, its quantitative capabilities lag behind its high spatial resolution and robustness. We develop a general method to transform the observables into quantitative force measurements. The force reconstruction algorithm has been deduced on the assumption that the observables (amplitude and phase shift) are slowly varying functions of the tip-surface separation. The accuracy and applicability of the method is validated by numerical simulations and experiments. The method is valid for liquid and air environments, small and large free amplitudes, compliant and rigid materials, and conservative and non-conservative forces.
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Affiliation(s)
- Amir F Payam
- Instituto de Ciencia de Materiales de Madrid, CSIC Sor Juana Inés de la Cruz 3 28049 Madrid, Spain
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Castañeda-Uribe OA, Reifenberger R, Raman A, Avila A. Depth-sensitive subsurface imaging of polymer nanocomposites using second harmonic Kelvin probe force microscopy. ACS NANO 2015; 9:2938-47. [PMID: 25591106 DOI: 10.1021/nn507019c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We study the depth sensitivity and spatial resolution of subsurface imaging of polymer nanocomposites using second harmonic mapping in Kelvin Probe Force Microscopy (KPFM). This method allows the visualization of the clustering and percolation of buried Single Walled Carbon Nanotubes (SWCNTs) via capacitance gradient (∂C/∂z) maps. We develop a multilayered sample where thin layers of neat Polyimide (PI) (∼80 nm per layer) are sequentially spin-coated on well-dispersed SWCNT/Polyimide (PI) nanocomposite films. The multilayer nanocomposite system allows the acquisition of ∂C/∂z images of three-dimensional percolating networks of SWCNTs at different depths in the same region of the sample. We detect CNTs at a depth of ∼430 nm, and notice that the spatial resolution progressively deteriorates with increasing depth of the buried CNTs. Computational trends of ∂C/∂z vs CNT depth correlate the sensitivity and depth resolution with field penetration and spreading, and enable a possible approach to three-dimensional subsurface structure reconstruction. The results open the door to nondestructive, three-dimensional tomography and nanometrology techniques for nanocomposite applications.
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Affiliation(s)
- Octavio Alejandro Castañeda-Uribe
- †Department of Electrical and Electronic Engineering and Centro de Microelectrónica (CMUA), Universidad de los Andes, Bogotá 11001, Colombia
| | | | | | - Alba Avila
- †Department of Electrical and Electronic Engineering and Centro de Microelectrónica (CMUA), Universidad de los Andes, Bogotá 11001, Colombia
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Guzman HV, Garcia PD, Garcia R. Dynamic force microscopy simulator (dForce): A tool for planning and understanding tapping and bimodal AFM experiments. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:369-79. [PMID: 25821676 PMCID: PMC4362491 DOI: 10.3762/bjnano.6.36] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 01/08/2015] [Indexed: 05/23/2023]
Abstract
We present a simulation environment, dForce, which can be used for a better understanding of dynamic force microscopy experiments. The simulator presents the cantilever-tip dynamics for two dynamic AFM methods, tapping mode AFM and bimodal AFM. It can be applied for a wide variety of experimental situations in air or liquid. The code provides all the variables and parameters relevant in those modes, for example, the instantaneous deflection and tip-surface force, velocity, virial, dissipated energy, sample deformation and peak force as a function of time or distance. The simulator includes a variety of interactions and contact mechanics models to describe AFM experiments including: van der Waals, Hertz, DMT, JKR, bottom effect cone correction, linear viscoelastic forces or the standard linear solid viscoelastic model. We have compared two numerical integration methods to select the one that offers optimal accuracy and speed. The graphical user interface has been designed to facilitate the navigation of non-experts in simulations. Finally, the accuracy of dForce has been tested against numerical simulations performed during the last 18 years.
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Affiliation(s)
- Horacio V Guzman
- Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juan Inés de la Cruz 3, 28049 Madrid, Spain
| | - Pablo D Garcia
- Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juan Inés de la Cruz 3, 28049 Madrid, Spain
| | - Ricardo Garcia
- Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juan Inés de la Cruz 3, 28049 Madrid, Spain
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Weber SAL, Kilpatrick JI, Brosnan TM, Jarvis SP, Rodriguez BJ. High viscosity environments: an unexpected route to obtain true atomic resolution with atomic force microscopy. NANOTECHNOLOGY 2014; 25:175701. [PMID: 24717916 DOI: 10.1088/0957-4484/25/17/175701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Atomic force microscopy (AFM) is widely used in liquid environments, where true atomic resolution at the solid-liquid interface can now be routinely achieved. It is generally expected that AFM operation in more viscous environments results in an increased noise contribution from the thermal motion of the cantilever, thereby reducing the signal-to-noise ratio (SNR). Thus, viscous fluids such as ionic and organic liquids have been generally avoided for high-resolution AFM studies despite their relevance to, e.g. energy applications. Here, we investigate the thermal noise limitations of dynamic AFM operation in both low and high viscosity environments theoretically, deriving expressions for the amplitude, phase and frequency noise resulting from the thermal motion of the cantilever, thereby defining the performance limits of amplitude modulation, phase modulation and frequency modulation AFM. We show that the assumption of a reduced SNR in viscous environments is not inherent to the technique and demonstrate that SNR values comparable to ultra-high vacuum systems can be obtained in high viscosity environments under certain conditions. Finally, we have obtained true atomic resolution images of highly ordered pyrolytic graphite and mica surfaces, thus revealing the potential of high-resolution imaging in high viscosity environments.
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Affiliation(s)
- Stefan A L Weber
- Conway Institute of Biomedical and Biomolecular Research, University College Dublin, Belfield, Dublin 4, Ireland. Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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