Crafting a good title for your research can be difficult. You need it to sound intriguing, yet still be firmly rooted in the reality and scope of your work. For this reason, research talks are quite often more interesting that you might be led to believe from the title alone, as the speaker has the chance to put their work into context and to communicate its true significance. In addition, titles generally highlight the broader scope of your research rather than making specific claims, which often come across as something of a sales pitch — not the greatest idea in a community that takes pride in its skepticism. What this can mean is that it may be hard to judge exactly what a research presentation is about, and whether or not it is interesting enough to attend.
Magnetic cilia?
This was the case two weeks ago, when Dr. Igor Aronson gave a seminar in my department. From the title of his talk, “Active Magnetic Colloids: from Self-Assembled Swimmers to Simple Robots“, I inferred that his research involved magnetically activated cilia on the surface of microparticles — a neat idea, but one that I had read about before and which did not seem like a terribly promising research avenue. I guess it didn’t help that the image printed on the flyer basically looked like a ciliated particle.
I’m glad I decided not to skip the talk, because the actual research was way cooler than my preconception. Basically, it consists of floating magnetic particles on a fluid surface in the presence of a magnetic field. When the field is static, each particle aligns itself with the field, and the aligned dipoles repel each other, spacing themselves out on the surface of the fluid. When the field is an alternating field, the rapid flipping of the floating particle dipoles allows for some attractive interactions between particles, and they form ordered assemblies of particles which writhe and motor rapidly around the surface of the liquid. (Check out a video here.)
The locomotion of these “snakes” seems to derive from a collective impelling of the liquid at both its ends, due to the oscillatory motions of the particles. If the snake is symmetric, the flows from either end offset, creating a rather efficient-looking pump:
This symmetry can be broken by placing a larger glass bead on one end, which results in roughly straight (OK, at least non-chaotic) locomotion:
When the magnetic particles are positioned at the interface between oil and water, both fluids are impelled by their oscillation, which leads to the formation of “asters”, single annular assemblies of particles. Due to the nature of the flow, larger particles will become trapped at the center of the aster, whose position can be remotely controlled using additional local magnetic fields. (This is what the image on the flyer was actually depicting.)
Looking back, Dr. Aronson’s title was certainly adequate, and not at all inaccurate, but my assumptions about the content of his talk almost led me to skip it to get some work done. However, I’m glad that I attended the talk, as I was able to learn about the really cool phenomenon of magnetic snakes.
