Aster moving a glass bead
The fodder for many science fiction stories, robots in the blood stream, has taken a step towards science reality. The bots are not little machines in this case, but a machine made of little ferromagnetic particles. From Argonne National Laboratories comes the "Asters."
Nicknamed by DOE-Argonne's physicists Alexey Snezhko and Igor Aronson. The partners figures a way to coax the particles, suspended in a fluid, to perform a few different operations. Under normal conditions, the particles are just aimlessly drifting through a fluid. Apply a alternating magnetic field perpendicular to the liquid's surface and the particles for a half-millimeter wide"star" shape, or Aster (Short for asterisk). If particles are lost in the Aster, the structure just reconfigures itself either autonomously or on command. In other words, the bots are self repairing.
From here the Asters are made to move using a second magnetic field. Aronson explained, "...apply a second small magnetic field parallel to the surface, they begin to move. The field breaks the symmetry of the asters' hydrodynamic flow, and the asters begin to swim." Full motion control was achieved using this method they discovered.
Using the principle, the Asters can also be manipulated to separate, creating a jaw like structure that can be used to pick up, transport, and drop non ferromagnetic objects. In the demonstration video, Asters are show to be able to move objects 10 times their own weight.
The team discovered that the asters can take on two different form configurations, flow either goes inward or outward. Depending on which direction the particles flow in the Aster determines the direction it moves. Using this discovery, the team was able to use the movement to precisely control the Asters in useful ways. For example, forming a "vacuum" collecting arrant particles.
This project is funded by the U.S. Department of Energy (DOE) for the purpose of understanding how to build and use active self-assembling materials. Who knows, maybe we will all have Asters in our blood stream.
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