INVITED PAPER: Instrumentation and Biological Applications of High-Resolution Frequency Modulation Atomic Force Microscopy in Liquid

2009 ◽  
Vol 4 ◽  
pp. 1-10 ◽  
Author(s):  
Takeshi Fukuma
Keyword(s):  
Atomic Force Microscopy ◽  
Frequency Modulation ◽  
Recent Progress ◽  
Imaging Techniques ◽  
Alkali Halides ◽  
Atomic Scale ◽  
Biological Applications ◽  
Force Microscopy ◽  
Organic Systems ◽  
Atomic Force

Frequency modulation atomic force microscopy (FM-AFM) has been a powerful tool for imaging atomic-scale structures and properties of various materials including metals, semiconductors, metal oxides, alkali halides and organic systems. Whilst the method has been used mainly in ultrahigh vacuum environments, recent progress in FM-AFM instrumentation made it possible to apply this technique also to investigations in liquid. This technological innovation opened up a variety of applications of FM-AFM in biology and electrochemistry. To date, the improved FM-AFM instrument and technique have been applied to investigations of several biological materials, providing novel information that has not been accessible with other imaging techniques. In this review, I will summarize the recent progress in FM-AFM instrumentation and biological applications in liquid.

Atomic-Scale Imaging of Surface and Hydration Structures of Stable and Metastable Acetaminophen Crystals by Frequency Modulation Atomic Force Microscopy

2018 ◽  
Vol 122 (38) ◽  
pp. 21983-21990
Author(s):  
Naritaka Kobayashi ◽  
Mihoko Maruyama ◽  
Yoichiro Mori ◽  
Suguru Fukukita ◽  
Hiroaki Adachi ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Frequency Modulation ◽  
Atomic Scale ◽  
Force Microscopy ◽  
Atomic Force

Subnanometer-scale imaging of nanobio-interfaces by frequency modulation atomic force microscopy

2020 ◽  
Vol 48 (4) ◽  
pp. 1675-1682
Author(s):  
Takeshi Fukuma
Keyword(s):  
Atomic Force Microscopy ◽  
Frequency Modulation ◽  
Critical Role ◽  
Surface Structures ◽  
Scale Model ◽  
Dynamic Mode ◽  
Biological Applications ◽  
Scanning Method ◽  
Force Microscopy ◽  
Atomic Force

Recently, there have been significant advancements in dynamic-mode atomic force microscopy (AFM) for biological applications. With frequency modulation AFM (FM-AFM), subnanometer-scale surface structures of biomolecules such as secondary structures of proteins, phosphate groups of DNAs, and lipid-ion complexes have been directly visualized. In addition, three-dimensional AFM (3D-AFM) has been developed by combining a high-resolution AFM technique with a 3D tip scanning method. This method enabled visualization of 3D distributions of water (i.e. hydration structures) with subnanometer-scale resolution on various biological molecules such as lipids, proteins, and DNAs. Furthermore, 3D-AFM also allows visualization of subnanometer-scale 3D distributions of flexible surface structures such as thermally fluctuating lipid headgroups. Such a direct local information at nano-bio interfaces can play a critical role in determining the atomic- or molecular-scale model to explain interfacial structures and functions. Here, we present an overview of these recent advancements in the dynamic-mode AFM techniques and their biological applications.

Improvements in fundamental performance of in-liquid frequency modulation atomic force microscopy

Microscopy ◽  
2020 ◽  
Vol 69 (6) ◽  
pp. 340-349
Author(s):  
Takeshi Fukuma
Keyword(s):  
Atomic Force Microscopy ◽  
Frequency Modulation ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Atomic Resolution ◽  
Scanning Method ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hydration Structure ◽  
Force Resolution

Abstract In-liquid frequency modulation atomic force microscopy (FM-AFM) has been used for visualizing subnanometer-scale surface structures of minerals, organic thin films and biological systems. In addition, three-dimensional atomic force microscopy (3D-AFM) has been developed by combining it with a three-dimensional (3D) tip scanning method. This method enabled the visualization of 3D distributions of water (i.e. hydration structures) and flexible molecular chains at subnanometer-scale resolution. While these applications highlighted the unique capabilities of FM-AFM, its force resolution, speed and stability are not necessarily at a satisfactory level for practical applications. Recently, there have been significant advancements in these fundamental performances. The force resolution was dramatically improved by using a small cantilever, which enabled the imaging of a 3D hydration structure even in pure water and made it possible to directly compare experimental results with simulated ones. In addition, the improved force resolution allowed the enhancement of imaging speed without compromising spatial resolution. To achieve this goal, efforts have been made for improving bandwidth, resonance frequency and/or latency of various components, including a high-speed phase-locked loop (PLL) circuit. With these improvements, now atomic-resolution in-liquid FM-AFM imaging can be performed at ∼1 s/frame. Furthermore, a Si-coating method was found to improve stability and reproducibility of atomic-resolution imaging owing to formation of a stable hydration structure on a tip apex. These improvements have opened up new possibilities of atomic-scale studies on solid-liquid interfacial phenomena by in-liquid FM-AFM.

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