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Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment

Scanning specimens in liquids using commercial atomic force microscopy (AFM) is very time-consuming due to the necessary try-and-error iteration for determining appropriate triggering frequencies and probes. In addition, the iteration easily contaminates the AFM tip and damages the samples, which co...

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Autor principal: Shih, Po-Jen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4118394/
https://www.ncbi.nlm.nih.gov/pubmed/24865882
http://dx.doi.org/10.3390/s140609369
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author Shih, Po-Jen
author_facet Shih, Po-Jen
author_sort Shih, Po-Jen
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description Scanning specimens in liquids using commercial atomic force microscopy (AFM) is very time-consuming due to the necessary try-and-error iteration for determining appropriate triggering frequencies and probes. In addition, the iteration easily contaminates the AFM tip and damages the samples, which consumes probes. One reason for this could be inaccuracy in the resonant frequency in the feedback system setup. This paper proposes a frequency function which varies with the tip-sample separation, and it helps to improve the frequency shift in the current feedback system of commercial AFMs. The frequency function is a closed-form equation, which allows for easy calculation, as confirmed by experimental data. It comprises three physical effects: the quasi-static equilibrium condition, the atomic forces gradient effect, and hydrodynamic load effect. While each of these has previously been developed in separate studies, this is the first time their combination has been used to represent the complete frequency phenomenon. To avoid “jump to contact” issues, experiments often use probes with relatively stiffer cantilevers, which inevitably reduce the force sensitivity in sensing low atomic forces. The proposed frequency function can also predict jump to contact behavior and, thus, the probe sensitivity could be increased and soft probes could be widely used. Additionally, various tip height behaviors coupling with the atomic forces gradient and hydrodynamic effects are discussed in the context of carbon nanotube probes.
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spelling pubmed-41183942014-08-01 Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment Shih, Po-Jen Sensors (Basel) Article Scanning specimens in liquids using commercial atomic force microscopy (AFM) is very time-consuming due to the necessary try-and-error iteration for determining appropriate triggering frequencies and probes. In addition, the iteration easily contaminates the AFM tip and damages the samples, which consumes probes. One reason for this could be inaccuracy in the resonant frequency in the feedback system setup. This paper proposes a frequency function which varies with the tip-sample separation, and it helps to improve the frequency shift in the current feedback system of commercial AFMs. The frequency function is a closed-form equation, which allows for easy calculation, as confirmed by experimental data. It comprises three physical effects: the quasi-static equilibrium condition, the atomic forces gradient effect, and hydrodynamic load effect. While each of these has previously been developed in separate studies, this is the first time their combination has been used to represent the complete frequency phenomenon. To avoid “jump to contact” issues, experiments often use probes with relatively stiffer cantilevers, which inevitably reduce the force sensitivity in sensing low atomic forces. The proposed frequency function can also predict jump to contact behavior and, thus, the probe sensitivity could be increased and soft probes could be widely used. Additionally, various tip height behaviors coupling with the atomic forces gradient and hydrodynamic effects are discussed in the context of carbon nanotube probes. MDPI 2014-05-26 /pmc/articles/PMC4118394/ /pubmed/24865882 http://dx.doi.org/10.3390/s140609369 Text en © 2014 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).
spellingShingle Article
Shih, Po-Jen
Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title_full Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title_fullStr Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title_full_unstemmed Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title_short Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment
title_sort frequency function in atomic force microscopy applied to a liquid environment
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4118394/
https://www.ncbi.nlm.nih.gov/pubmed/24865882
http://dx.doi.org/10.3390/s140609369
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