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Flagella seem to embody simplicity on the microscopic scale. But appearances can be deceptive: they are composed of 650 different types of proteins. (Credit: iStockphoto)

flagella

How to make tiny robots move like flagella

The whip-like organelles that help sperm swim and sponges eat have a fluid movement that is difficult to mimic in microrobots.

Scientists have struggled to build a simple, controllable model that can recreate how flagella move.

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Now, Michael Hagan, associate professor of physics at Brandeis University, and researchers in his lab have built the first viable computer model to generate flagella-like movement with man-made structures.

Hagan’s computer model significantly simplifies the motion of complex flagella, using spherical self-propelled particles called colloids in a structure resembling a string of beads. The colloids exert pressure on themselves, causing the filament to beat.

Just the right strength and length

Flagella seem to embody simplicity on the microscopic scale. But appearances can be deceptive: they are composed of 650 different types of proteins.

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Their length depends on their purpose but flagellas’ structure and rhythmic, beating movement remain the same across functions and species.

To make the model viable, the team first had to figure out the proper strength of the colloids’ attachment. If the connections were too tight, the string would be stiff and unmoving; too loose, and it would be floppy and ineffective.

Next, Hagan determined the length of the filament required for motion—too short or too long and it wouldn’t be able to propel anything.

After determining the strength and length of the filament, the team anchored one end of it, as if to a cell wall, and observed those graceful, beating motions on their computer model.

“Because this system is so simple, and its construction so different from that of flagella, we should be able to elucidate the most fundamental features of flagella that give rise to and control motion. These features can be understood without having to unravel all 650 moving parts of a flagellum,” Hagan says.

The research may pave the way to develop flagella-like microrobots to carry drugs to targeted cells, or fertilize an egg, or to create microfluidic devices that could pump and circulate fluid.

Hagan’s research is published in the Journal of Royal Society Interface, coauthored by former Brandeis University postdoctoral fellows Raghunath Chelakkot and Arvind Gopinath, along with L. Mahadevan, professor of physics, biology, and applied mathematics, at Harvard University. The Material Research Science and Engineering Center at Brandeis University funded the work.

Source: Brandeis University

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