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RHEOSafm is an extension of the software package written in the Julia programming language RHEOS that provides tools for importing and preprocessing rheological data collected using Atomic Force Microscopy.
Atomic Force Microscopy (AFM) is a widely experimental technique used by scientist and engineers to study the local mechanical response of materials. The key AFM component is a nanoscale tip attached to a cantilever that is indented within the material. The deflection of the cantilever is read via a laser directly pointed towards the indenting end of the cantilever. By knowing the spring constant of the cantilever and the deflection of the laser, the force applied to the sample can be calculated.
There are different modes of operation in which an AFM can be used. The easiest way is to indent the probe at constant rate within the sample with a given force while recording the tip deflection. Another common class of tests are known as viscoelastic measurements: the cantilever is indented within the sample at a given force, and the force or the measured displacement is kept constant for a given time (i.e. creep and relaxation tests). The recorded time-force-displacement values allow us to extract the mechanical properties of the tested material.
The determination of such unique parameters that describe a material requires two main steps:
- a contact model to convert force and displacement into stress and strain
- a relationship between time-stress-strain (often referred to as constitutive model) Although most of commercial AFM software programs provide a wide variety of processing tools to extract material parameters, those are limited to approximation of an elastic material, thus allowing the user to only extract the Young's modulus. Here we provide a preprocessing interface to transform time-force-displacement values into time-stress-strain that can be directly processed within RHEOS. This interface allows the user to fit the experimental data not only with a simple elastic model, but with a wide variety of viscoelastic constitutive models (for more information refer to RHEOS models).
RHEOSafm package provides the utilities to:
- build a direct interface with a widely commercially available testing set-up, RHEOSafm provides features to directly import experimental data collected using BRUKER - JPK products;
- identify the contact point.
The sections in this documentation each aim to provide tutorials for the elements of RHEOSafm. For more information regarding the functionalities of RHEOS please refer to RHEOS documentation.
- Install Julia (latest version recommended)
- From interactive command-line Julia REPL, enter pkg mode by pressing
] - (Optional) Enable desired Project.toml environment
- Run the command
add RHEOSto install the main RHEOS software package - Run the command
add https://github.com/JuliaRheology/RHEOSafm.jlto install the extension RHEOSafm
If you believe you have found any bugs or invalid behaviour in RHEOSafm, please feel free to file an issue on this repository. You can also raise an issue if you feel that any part of the documentation needs clarification, or for any feature requests. Even better than just raising an issue, you could both raise an issue and issue a pull request which fixes that issue. Please be aware that RHEOSafm is released with a Contributor Code of Conduct and by participating in this project you agree to abide by its terms.
If you use RHEOSafm in your work, please consider citing the following papers as appropriate:
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J. L. Kaplan, A. Bonfanti, A. J. Kabla (2019). RHEOS.jl -- A Julia Package for Rheology Data Analysis. Journal of Open Source Software, 4(41), 1700, https://doi.org/10.21105/joss.01700
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A. Bonfanti, J. L. Kaplan, G. Charras, A. J. Kabla (2020). Fractional viscoelastic models for power-law materials. Soft Matter, 16, 6002-6020, https://doi.org/10.1039/D0SM00354A