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1. Large-range high-speed dynamic-mode atomic force microscope imaging: adaptive tapping towards minimal force

   https://doi.org/10.1088/1361-6528/acd700  

   Chen, Jiarong; Zou, Qingze (May 2023, Nanotechnology)

   Abstract This paper presents a software-hardware integrated approach to high-speed large-range dynamic mode imaging of atomic force microscope (AFM). High speed AFM imaging is needed to interrogate dynamic processes at nanoscale such as cellular interactions and polymer crystallization process. High-speed dynamic-modes such as tapping-mode AFM imaging is challenging as the probe tapping motion is sensitive to the highly nonlinear probe-sample interaction during the imaging process. The existing hardware-based approach via bandwidth enlargement, however, results in a substantially reduction of imaging area that can be covered. Contrarily, control (algorithm)-based approach, for example, the recently developed adaptive multiloop mode (AMLM) technique, has demonstrated its efficacy in increasing the tapping-mode imaging speed without loss of imaging size. Further improvement, however, has been limited by the hardware bandwidth and online signal processing speed and computation complexity.Thus, in this paper, the AMLM technique is further enhanced to optimize the probe tapping regulation and integrated with a field programmable gate array (FPGA) platform to further increase the imaging speed without loss of imaging quality and range. Experimental implementation of the proposed approach demonstrates that the high-quality imaging can be achieved at a high-speed scanning rate of 100 Hz and higher, and over a large imaging area of over 20 µm. 

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2. Nanomechanical mapping in air or vacuum using multi-harmonic signals in tapping mode atomic force microscopy

   https://doi.org/DOI: 10.1088/1361-6528/ab9390  

   Shaik, N. H. (August 2020, Nanotechnology)

   We present a method by which multi-harmonic signals acquired during a normal tapping mode (amplitude modulated) AFM scan of a sample in air or vacuum with standard microcantilevers can be used to map quantitatively the local mechanical properties of the sample such as elastic modulus, adhesion, and indentation. The approach is based on the observation that during the tapping mode operation in air or vacuum, the 0th and 2nd harmonic signals of microcantilever vibration are encountered under most operating conditions and can be mapped with sufficient signal to noise ratio. By measuring the amplitude and phase of the driven harmonic as well as the 0th and 2nd harmonic observables, we find analytical/semi-analytical formulas that relate these multi-harmonic observables to local mechanical properties for several classical tip-sample interaction models. Least squares estimation of the local mechanical properties is performed pixel by pixel. The method is validated through computations as well as experimental data acquired on a polymer blend made of Polystyrene and Polyolefin elastomer. 

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3. High-speed large-range dynamic-mode atomic force microscope imaging: Adaptive tapping approach via Field Programmable Gate Array

   Chen, Jiarong; Zou, Qingze (July 2020, Proceedings of the American Control Conference)
4. Investigation of temperature induced mechanical changes in supported bilayers by variants of tapping mode atomic force microscopy: Investigation of mechanical changes in bilayers

   https://doi.org/10.1002/sca.21175  

   Shamitko-Klingensmith, Nicole; Legleiter, Justin (January 2015, Scanning)
5. Correlation of Atomic Force Microscopy Tapping Forces to Mechanical Properties of Lipid Membranes

   https://doi.org/10.1115/DETC2012-70233  

   Shamitko-Klingensmith, Nicole; Wambaugh, Kelley M.; Burke, Kathleen A.; Magnone, George J.; Legleiter, Justin (August 2012, ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference)

   There is considerable interest in measuring, with nanoscale spatial resolution, the physical properties of lipid membranes because of their role in the physiology of living systems. Due to its ability to nondestructively image surfaces in solution, tapping mode atomic force microscopy (TMAFM) has proven to be a useful technique for imaging lipid membranes. However, further information concerning the mechanical properties of surfaces is contained within the time-resolved tip/sample force interactions. The tapping forces can be recovered by taking the second derivative of the cantilever deflection signal and scaling by the effective mass of the cantilever; this technique is referred to as scanning probe acceleration microscopy. Herein, we describe how the maximum and minimum tapping forces change with surface mechanical properties. Furthermore, we demonstrate how these changes can be used to measure mechanical changes in lipid membranes containing cholesterol. 

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