Search query: AFM

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abstract: Atomic force microscopy based infrared spectroscopy (AFM IR) is a rapidly emerging technique that provides chemical analysis and compositional mapping with spatial resolution far below conventional optical diffraction limits. AFM IR works by using the tip of an AFM probe to locally detect thermal expansion in a sample resulting from absorption of infrared radiation. AFM IR thus can provide the spatial resolution of AFM in combination with the chemical analysis and compositional imaging capabilities of infrared spectroscopy. This article briefly reviews the development and underlying technology of AFM IR, including recent advances, and then surveys a wide range of applications and investigations using AFM IR. AFM IR applications that will be discussed include those in polymers, life sciences, photonics, solar cells, semiconductors, pharmaceuticals, and cultural heritage. In the Supporting Information the authors provide a theoretical section that reviews the physics underlying the AFM IR measurement and detection mechanisms.
author_names: Alexandre Dazzi

Craig B Prater
title: AFM IR: Technology and Applications in Nanoscale Infrared Spectroscopy and Chemical Imaging.
venue: Chemical reviews
year: 2017

abstract: Single molecule atomic force microscopy (AFM) was used to investigate the mechanical properties of titin, the giant sarcomeric protein of striated muscle. Individual titin molecules were repeatedly stretched, and the applied force was recorded as a function of the elongation. At large extensions, the restoring force exhibited a sawtoothlike pattern, with a periodicity that varied between 25 and 28 nanometers. Measurements of recombinant titin immunoglobulin segments of two different lengths exhibited the same pattern and allowed attribution of the discontinuities to the unfolding of individual immunoglobulin domains. The forces required to unfold individual domains ranged from 150 to 300 piconewtons and depended on the pulling speed. Upon relaxation, refolding of immunoglobulin domains was observed.
author_names: M Rief

Mathias Gautel

Filipp Oesterhelt

J M Fernandez

Hermann Eduard Gaub
title: Reversible unfolding of individual titin immunoglobulin domains by AFM.
venue: Science
year: 1997

abstract: Currently, biomechanics of living cells is in the focus of interest due to noticeable capability of such techniques like atomic force microscopy (AFM) to probe cellular properties at the single cell level directly on living cells. The research carried out, so far, delivered data showing, on the one hand, the use of cellular mechanics as a biomarker of various pathological changes, which, on the other hand, reveal relative nature of biomechanics. In the AFM, the elastic properties of living cells are delivered from indentation experiments and described quantitatively by Young's modulus defined here as a measure of cellular deformability. Here, the AFM studies directly comparing the mechanical properties of normal and cancerous cells are summarized and presented together with a few important issues related to the relativeness of Young's modulus.
author_names: Malgorzata Lekka
title: Discrimination Between Normal and Cancerous Cells Using AFM
venue: BioNanoScience
year: 2016

abstract: High resolution Atomic Force Microscopy (AFM) and Scanning Tunnelling Microscopy (STM) imaging with functionalized tips is well established, but a detailed understanding of the imaging mechanism is still missing. We present a numerical STM/AFM model, which takes into account the relaxation of the probe due to the tip sample interaction. We demonstrate that the model is able to reproduce very well not only the experimental intra and intermolecular contrasts, but also their evolution upon tip approach. At close distances, the simulations unveil a significant probe particle relaxation towards local minima of the interaction potential. This effect is responsible for the sharp sub molecular resolution observed in AFM/STM experiments. In addition, we demonstrate that sharp apparent intermolecular bonds should not be interpreted as true hydrogen bonds, in the sense of representing areas of increased electron density. Instead they represent the ridge between two minima of the potential energy landscape due to neighbouring atoms.
author_names: Prokop Hapala

Georgy Kichin

Christian Wagner

F Stefan Tautz

Ruslan Temirov

Pavel Jelinek
title: Mechanism of high resolution STM/AFM imaging with functionalized tips
year: 2014

abstract: A current challenge in the life sciences is to understand how biological systems change their structural, biophysical and chemical properties to adjust functionality. Addressing this issue has been severely hampered by the lack of methods capable of imaging biosystems at high resolution while simultaneously mapping their multiple properties. Recent developments in force distance (FD) curve based atomic force microscopy (AFM) now enable researchers to combine (sub)molecular imaging with quantitative mapping of physical, chemical and biological interactions. Here we discuss the principles and applications of advanced FD based AFM tools for the quantitative multiparametric characterization of complex cellular and biomolecular systems under physiological conditions.
author_names: Yves F Dufrene

David Martinez-Martin

Izhar D Medalsy

David Alsteens

Daniel J Muller
title: Multiparametric imaging of biological systems by force distance curve based AFM
venue: Nature Methods
year: 2013

abstract: The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH) temperature and anion type, which might be linked to volume changes (swelling and shrinkage) Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, stratlingite, hydroxy AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions. (C) 2015 Elsevier Ltd. All rights reserved.
author_names: Luis G Baquerizo

Thomas Matschei

Karen Scrivener

Mahsa Saeidpour

Lars Wadso
title: Hydration states of AFm cement phases
year: 2015

abstract: Polymer and life science applications of a technique that combines atomic force microscopy (AFM) and infrared (IR) spectroscopy to obtain nanoscale IR spectra and images are reviewed. The AFM IR spectra generated from this technique contain the same information with respect to molecular structure as conventional IR spectroscopy measurements, allowing significant leverage of existing expertise in IR spectroscopy. The AFM IR technique can be used to acquire IR absorption spectra and absorption images with spatial resolution on the 50 to 100 nm scale, versus the scale of many micrometers or more for conventional IR spectroscopy. In the life sciences, experiments have demonstrated the capacity to perform chemical spectroscopy at the sub cellular level. Specifically, the AFM IR technique provides a label free method for mapping IR absorbing species in biological materials. On the polymer side, AFM IR was used to map the IR absorption properties of polymer blends, multilayer films, thin films for active devices such as organic photovoltaics, microdomains in a semicrystalline polyhydroxyalkanoate copolymer, as well as model pharmaceutical blend systems. The ability to obtain spatially resolved IR spectra as well as high resolution chemical images collected at specific IR wavenumbers was demonstrated. Complementary measurements mapping variations in sample stiffness were also obtained by tracking changes in the cantilever contact resonance frequency. Finally, it was shown that by taking advantage of the ability to arbitrarily control the polarization direction of the IR excitation laser, it is possible to obtain important information regarding molecular orientation in electrospun nanofibers.
author_names: Alexandre Dazzi

Craig B Prater

Qichi Hu

D Bruce Chase

John F Rabolt

Curtis Marcott
title: AFM IR: Combining Atomic Force Microscopy and Infrared Spectroscopy for Nanoscale Chemical Characterization
venue: Applied spectroscopy
year: 2012

abstract: The stiffness of cancer cells and its changes during metastasis are very important for understanding the pathophysiology of cancer cells and the mechanisms of metastasis of cancer. As the first step of the studies on the mechanics of cancer cells during metastasis, we determined the elasticity and stiffness of cancer cells with an indentation method using an atomic force microscope (AFM) and compared with those of normal cells. In most of the past AFM studies, Young's elastic moduli of cells have been calculated from force indentation data using Hertzian model. As this model is based on several important assumptions including infinitesimal strain and Hooke's linear stress strain law, in the exact sense it cannot be applied to cells that deform very largely and nonlinearly. To overcome this problem, we previously proposed an equation F=a[exp(bd) 1] to describe relations between force (F) and indentation (d) where a and b are parameters relating with cellular stiffness. In the present study, we applied this method to cancer cells instead of Young's elastic modulus. The conclusions obtained are: 1) AFM indentation test data of cancer cells can be very well described by the above equation, 2) cancer cells are softer than normal cells, and 3) there are no significant locational differences in the stiffness of cancer cells between the central and the peripheral regions. These methods and results are useful for studying the mechanics of cancer cells and the mechanisms of metastasis.
author_names: Kozaburo Hayashi

Mayumi Iwata
title: Stiffness of cancer cells measured with an AFM indentation method.
venue: Journal of the mechanical behavior of biomedical materials
year: 2015

abstract: An atomic force microscope (AFM) is an extremely versatile investigative tool in the field of nanotechnology, the performance of which is significantly influenced by its conventional zig zag raster pattern scanning method. In this paper, in order to increase its imaging speed, we consider the use of a sinusoidal scanning method, i.e. a spiral scanning method with an improved model predictive control (MPC) scheme. In this approach, spirals are generated by applying waves, each with a single frequency and slowly varying amplitude, in the X piezo (sine wave) and Y piezo (cosine wave) of the piezoelectric tube scanner (PTS) of the AFM. As these input signals are single frequencies, the scanning can proceed faster than traditional raster scanning, without exciting the resonant mode of the PTS. The proposed MPC controller reduces the phase error between the reference position input and measured output sinusoids and provides better tracking of the reference signal. Also, a notch filter is designed and included in the feedback loop to suppress vibrations of the PTS at the resonant frequency. The experimental results show that, using the proposed method, the AFM is able to scan a 6 mm radius image within 2.04 s with a quality better than that obtained using the conventional raster pattern scanning method.
author_names: M S Rana

Hemanshu Roy Pota

Ian R Petersen
title: Performance of Sinusoidal Scanning With MPC in AFM Imaging
venue: IEEE/ASME Transactions on Mechatronics
year: 2015

abstract: The ability to perturb individual cells and to obtain information at the single cell level is of central importance for addressing numerous biological questions. Atomic force microscopy (AFM) offers great potential for this prospering field. Traditionally used as an imaging tool, more recent developments have extended the variety of cell manipulation protocols. Fluidic force microscopy (FluidFM) combines AFM with microfluidics via microchanneled cantilevers with nano sized apertures. The crucial element of the technology is the connection of the hollow cantilevers to a pressure controller, allowing their operation in liquid as force controlled nanopipettes under optical control. Proof of concept studies demonstrated a broad spectrum of single cell applications including isolation, deposition, adhesion and injection in a range of biological systems.
author_names: Orane Guillaume-Gentil

Eva Potthoff

Dario Ossola

Clemens M Franz

Tomaso Zambelli

Julia A Vorholt
title: Force controlled manipulation of single cells: from AFM to FluidFM.
venue: Trends in biotechnology
year: 2014