Ever wonder how a germ knows where to attack the body or how a white blood cell knows where to counter attack? How bacteria find food? Or how cells organize themselves to close a wound? How can something so simple do things so complex? A team of MIT researchers is seeking the answers as they develop "microwalkers" – microscopic machines that can move unguided across the surface of a cell as they seek out particular areas.

Though they may not seem so at first glance, microorganisms are remarkable pieces of engineering. Lacking nervous systems, senses, or any way of understanding the world around them, they can look for and find places in the body or on cell surfaces where they can carry out their functions.

Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering and his team at MIT believe that if they can mimic this process, it will provide scientists with a valuable tool for constructing sensors and medical devices that can find their way to specific areas of a cell surface without outside guidance.

The MIT microwalker system is, like that of microorganisms, based on friction. On cell membranes, areas with a concentration of cell receptors tend to be rougher. White blood cells and other microorganisms use these friction gradients to find their destination in a sort of blind man's bluff called "chemotaxis" as they feel their way along. What the MIT team is trying to do is come up with a mechanical way of duplicating this.

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