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Cephalopod City!

Welcome to the squid skin simulator! The code here can be used to generate the simulations from the paper: http://rsif.royalsocietypublishing.org/content/12/108/20150281

Cephalopods are awesome, especially the way their skin rapidly changes colour. https://www.youtube.com/watch?v=PmDTtkZlMwM

The magic is in their chromatophores cells - https://www.youtube.com/watch?v=1pJPnZFSy5o - these little ones expand and contract to change the host's perceived skin colour. Perhaps one day we could mimic their chromomorphic wizardry into something wearable.

Here we consider Dielectric Elastomer coated with a bunch of coloured electrodes that serve as the cells. Three independantly controlled artificial chromatophores have already been fabricated: https://www.youtube.com/watch?v=W2CgtJU3ckY

By coordinating cell actuation in a cellular-automata like fashion, we can impose simple rules that yield complex patterns which propagate over the surface of the skin.

Videos generated with this simulator:

• Type II Behaviour https://www.youtube.com/watch?v=H5wG2jPh2cE
• Type III Behaviour https://www.youtube.com/watch?v=nWg-Lu5Xzm8

This was the first non-tiny MATLAB project I have ever done... and I didn't enjoy the way they implemented objects. The lack of package management also makes it hard to grow projects. Also its proprietary-ness makes this code less accessible for many people. In the future I'd like to make these things more accesible :)

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Performing simulations:

Look at the examples in the /Sims/ folder for direction.

Basic flow is:

1. Construct a Thread object

2. Construct a SimulateThread object using that thread

3. On the SimulateThread object use RunSim to run a simulation from the start (which will OVERWRITE any previous data of the same name)

Since large threads take rather long to simulate you can crtl+c out of them. They can be continued with the static SimulateThread.ContinueSim(name, tMax) method. This can help if you want to view the output as you go along.

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Output format:

Output data from the SimulateThread.m class is stored in the /Sims/ folder with two files:

• <name>.csv stores time, local state and global state data
• <name>.mat stores the instance of the SimulateThread object

There are scripts in the /Sims/ folder that generate the simulations using each type of behaviour discussed in the paper.

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Viewing the Output:

Use the SimViewer class for this. If too much data is being loaded during class construction, include the resolution argument

SimViewer contains many functions to view output. Your best buddies here are:

• PlotMaterial
• PlotGlobal

TODO: talk about report generation

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Constructing Threads:

When you construct your thread, view it with Thread.Plot

In general, use the static Thread.ConstructThreadWithSpacedElectrodes to construct your thread (the actual Thread constructor provides a more flexible way, but will require more work to make it sim ready). This makes a thread with equally spaced, locally controlled electrodes, with the first electrode externally controlled

WARNING: This tries to figure out the coarsest possible element length, so keep an ```I''' on it. If it messes up you might get one that is stupidly coarse (though it works as it should for the provided sims)

Prior to constructing the thread you'll need to construct the following:

• LocalSwitchingModel (for the self-sensing cells, look in the SwitchingModelsLocal folder)
• ExternalSwitchingModel (look in the SwitchingModelsExternal folder, includes cyclic/step)
• ... as well as arguments for the number of cells, prestretch, their dimensions and spacing

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Adjusting Other model parameters:

Other things that you may want to adjust:

• Element subclasses
• MaterialParameters