arXiv subjects

Kenichi Umeda

Publications and source records attributed to Kenichi Umeda.

5 recordsLinked to original sources

arXiv2026

UMEX Viewer - Software Suite for High-Speed AFM Data Analysis and Its Applications

Recent technical advances in atomic force microscopy (AFM) have led to the development of high-speed AFM (HS-AFM), which enables video-rate imaging and direct visualization of the nanoscale dynamics of biomolecules functioning in solution. Because HS-AFM rapidly generates large datasets, dedicated software is essential for efficient processing, organization, and analysis. Recent improvements in imaging speed have further increased data throughput, underscoring the need for faster analysis software with improved usability. To address this need, we developed Ultrafast Microscopy Exploration (UMEX) Viewer, a software suite for HS-AFM data analysis. UMEX Viewer provides an integrated environment for HS-AFM data handling, including image processing, drift correction, image and movie export, data management, and quantitative analysis. These capabilities have enabled the software to be applied to a wide range of recent studies. In this article, we describe the core functions of UMEX Viewer and demonstrate its practical applications for HS-AFM data analysis aimed at elucidating biological functions.

physics.app-ph↗

arXiv2026

Feedforward Compensation of Piezo Nonlinearity for High-Precision High-Speed Atomic Force Microscopy

Atomic force microscopy (AFM) enables nanoscale characterization and has been widely applied to a broad range of systems. Over the past two decades, advances in high-speed AFM have enabled not only the imaging of static structures but also the direct observation of nanoscale dynamics in real time. However, because the tip or sample is typically scanned using piezoelectric actuators, nonlinearities in their response to the input signal can introduce image-scaling errors of up to 20-30%. Consequently, there is a strong demand for a method to correct piezoelectric nonlinearity that can reliably support quantitative dynamic structural measurements. Here, we propose a simple software-based feedforward method to generate scan waveforms that can be readily implemented. We identify four distinct sources of positioning error in piezo scanners and demonstrate that these errors can be compensated, achieving an order-of-magnitude improvement in positioning accuracy compared with uncompensated operation. Because the proposed method is software-based and requires no additional hardware, it preserves imaging speed and is well suited for high-speed AFM. It is also compatible with a wide range of AFM and other scanning probe systems.

physics.app-ph↗

arXiv2025

Excitation frequency dependence of noise and minimum detectable force in amplitude-modulation atomic force microscopy

Atomic force microscopy (AFM) is a versatile nanoscale imaging technique. Since its spatiotemporal resolution is fundamentally limited by the minimum detectable force (MDF) arising from system noise, a deep understanding of MDF is essential for improving instrumentation. However, the theoretical MDF of amplitude-modulation (AM) AFM has long remained inconsistent, with three reported expressions yielding conflicting coefficients: 1.84, 1.41, and 0.71 times those of other dynamic modes. Moreover, although we recently clarified the strong dependence of force sensitivity on the cantilever's driving frequency, previous theories overlooked this effect. Here, we present an exact solution for the MDF of AM-AFM that accounts for noise frequency dependence, excitation efficiency, and arbitrary cantilever Q-factors. Our results clarify that the coefficient strongly depends on the driving frequency and Q-factor. Notably, when driven at the resonance slope, it stays within 1 and 1.41, thus resolving this long-standing inconsistency. Our findings provide essential guidance for improving instrumentation to visualize previously inaccessible phenomena.

physics.app-ph↗

arXiv2024

Quantitative Formulation of Frequency-Dependent Average Force in AM-AFM

Amplitude-modulation atomic force microscopy (AM-AFM) measures nanoscale surface structures by detecting changes in the cantilever oscillation amplitude, contributing to materials research. AM-AFM can non-destructively observe fragile molecules, such as biomolecules, even while the probe is in intermittent contact with the sample. However, it remains unclear why the tip-sample interaction force estimated from an experimental amplitude value is substantially greater than the actual molecular binding force, despite the successful visualization of molecular dynamics. Here, we formulate a quantitative force conversion equation for arbitrary driving frequencies. Comprehensive theoretical analysis reveals that when the cantilever is excited at the resonance slope, the conventional equation overestimates the actual force by approximately five times, as it is valid only for excitation at the resonance frequency. The theory is validated by simulations and experiments and can be applied to various AM-AFM applications in materials research.

physics.app-ph↗

arXiv2024

Guidelines for Fast and Nondestructive Imaging in AM-AFM

Amplitude-modulation atomic force microscopy enables observation of fragile molecules at the nanometer scale. To shorten measurement times and capture dynamic molecules, increasing the frame rate is essential. Traditionally, maximum frame rates were thought to be limited by device bandwidth. However, for fragile molecules, imaging speed is often constrained by disruption from tip-sample interaction forces. Despite its significance, no comprehensive theoretical study has addressed this limitation. Here, we establish guidelines for high-speed, nondestructive AM-AFM imaging of fragile molecules. Our analysis identifies two types of forces: an impulsive force on the molecule's uphill side and a steady force linked to error saturation on the downhill side. By examining the frequency dependence of the amplitude-distance curve, we demonstrate that exciting at the resonance slope minimizes feedback error forces and allows for their easy estimation using simple equations. These findings provide valuable insights for studying fragile materials, particularly biomolecules.

physics.app-ph↗