AFM point-mass model with DMT tip-sample interaction

AFM point-mass Simulink model with DMT interaction. Outputs amplitude & phase observables. Packaged as AFM_by_JRR for MATLAB.

Project Overview

This repository provides a clean, self-contained Simulink model paired with a MATLAB automation script to simulate dynamic Amplitude Modulation AFM (AM-AFM / Tapping Mode). The simulator utilizes point-mass cantilever dynamics interacting with a sample surface via a mathematically continuous and precise formulation of Derjaguin-Muller-Toporov (DMT) contact mechanics.

By ensuring a correct physical and mathematical transition at the contact interface threshold (d=a0​), the model leverages MATLAB's high-performance ode15s (stiff) solver instead of traditional, inefficient Runge-Kutta methods. This drastically eliminates solver stalling and enables fast, robust parameter sweeps.

Academic Validation

The simulation parameters and physical constants implemented in this project are rigorously benchmarked against literature, specifically adapted from:

Page 211 of García, R. and Pérez, R., 2002. Dynamic atomic force microscopy methods. Surface Science Reports, 47(6-8), pp.197-301.

What’s Included in the Box

Download and extract the provided afm_by_jrr.zip file to access the complete standalone simulator suite:

• afm.slx – The core physical engine housing the point-mass differential equations, virtual lock-in amplifier, and the non-linear DMT interaction function block.
• parameters_DMT.m – The complete configuration dataset containing the precise material and cantilever properties cited from the García & Pérez reference text.
• amplitude_and_phase.m – The master driver script that defines the sweep variables, coordinates the batch Simulink runs, and extracts the final steady-state data.

Quick Start

1. Unzip the archive into your preferred directory.
2. Open MATLAB and navigate to that folder.
3. Run the script Amplitude_vs_Phase.m to execute the simulation and view the outputs.

Expected Output

When you open the project and run the script with the default parameter set, the system automatically sweeps the tip-sample separation. The output cleanly maps out the classic AM-AFM curves, capturing the signature bistable oscillation regime (the sudden, hysteretic jump between the attractive non-contact state and the repulsive contact state) exactly as seen in physical experiments.

Future Roadmap (AFM_by_JRR)

This project serves as the foundation for the AFM_by_JRR tool suite. It is designed from the ground up to be fully modular and scalable. Future updates to this package will expand on this framework to include alternative contact mechanics models (e.g., JKR, viscoelastic damping) and other AFM-related topics.

Feedback & Contributions

If you find this model helpful for your research, lab group, or coursework, please leave a rating or a comment! For technical questions, bugs, or feature requests, feel free to start a discussion in the comments below.