The same kind of patterns can be seen at the microscopic scale in colonies of bacteria or in living tissues.
And recently, I've been working on non-living microscopic particles that self-propel, displaying the same kind of patterns.
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| Long exposure picture of self-propelled particles |
A lot of beautiful physics has been done in the last decade about this class of system. Now it's known as "Active Matter".
Patterns are mesmerizing, physics is intellectually pleasing, but what is the purpose? What do you make out of this "Active Matter"? Can you build a bridge? Power your home? Cure cancer ?
Well, maybe.
It becomes clearer by the day that cancer metastasis is a swarm of cancer cells migrating through the body, very close to the above patterns. In which conditions the solid tumour becomes a liquid-like swarm? How to influence this transition? These are actual questions physicists and biophysicists are asking right now.
Maybe you can't power a house with active matter, but maybe you can make it do the worm of pumping the water of your shower. It has been found that a suspension of swimming micro-organisms flow more readily (has a lower viscosity) than the suspension of dead micro-organisms. Furthermore, in some situations, the viscosity is even lower than the liquid alone, without micro-organisms! They swim, converting their food into movement, and this moment helps the water flow up the pipe.
And can we build something? Maybe not a bridge, but a muscle that would be able to contract from the action of trillions of micro-motors. Or some kind of new material that would react to a push to the left by deforming to the right?
To understand this last point, I am looking for a PhD student interested in physics, mechanics, materials and afraid neither to code nor to perform experiments. This is an experimental investigation. See the announcement (2 pages, FR then EN) on my lab's website.
