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Application of AC current injection through surface electrodes in frequency domain analysis in skin
Posted Feb 7, 2024, 1:15 p.m. EST 4 Replies
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Hello, I have been looking for a method to inject AC current through skin surface electrodes and perform frequency domain analysis at each time point (represented by a parametric sweep across various geometrical changes). This is low amperage and betwen 10KHz to 100KHz.
I am unsure how to perform this analysis or go about specifying the AC current source frequency since I am analyzing in the frequency domain, not in time. Ideally, I would like to sweep across multiple frequencies to test electrode performance.
Thank you.
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- You can do a frequency sweep in frequency domain. If time truly doesn't matter from the perspective of the physics, then you don't have to care about it. If you wish, you can (mentally, or with a pencil and paper) associate each frequency with whatever time you wish (e.g., "If this is Belgium, it must be Thursday.") Now, if the physics involved actually depend on time, then you should use a time-domain model. But I doubt that is the case here.
- Based on your description, I suspect you will be (or should be) using the Electric Currents (EC) interface, which is part of the AC/DC module. That's where I would start, anyway. That should support your frequency domain model. You'll need to specify the conductivity of the skin/flesh, of course. I hope that helps.
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Hello Robert,
Thank you for your reply. Your advice is very helpful. I am using the EC interface model from the AC/DC module. The main concern that I had is, how do I define my input current as an AC signal. I use a simple "Terminal" definition for the injection current at 0.4mA and a "Ground". This is where I'm curious as to how to define a driving frequency of 10kHz for the AC current at Terminal 1? Is this accomplished through simply defining the freq in frequency domain study? To respond to point 1: to the best of my knowledge (I may be complete wrong), but in this case I simulate "time" by doing a parametric sweep of the geometrical changes with time that has been calculated previously. Since the physical changes are expected to be significantly slower than AC freq, this should be ok.
Thank you very much, I greatly appreciate your kind assistance.
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Defining the frequency in the frequency domain study does indeed define the frequency. If/when you specify 0.4mA for the input current, that will then set the amplitude of the implied sinusoidal current (at the subject frequency) to 0.4mA. I'm not entirely sure what you are doing in detail in regard to this or your other boundary conditions, but I think (tentatively) that you are on the right track. You might also want to check if there are some similar (even if just vaguely similar) models in the Comsol-supplied Application Library.
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Hello, See, for example, these resources:
https://www.comsol.com/support/learning-center/article/27591/132
https://www.comsol.com/blogs/understanding-the-excitation-options-for-modeling-electric-currents/
https://www.comsol.com/blogs/modeling-dispersion-in-an-electric-currents-model/