Dust-Size "Crabs" Grab Living Cells in Lab Video

Christine Dell'Amore
National Geographic News
January 26, 2009

New wireless machines the size of dust particles can grab and manipulate tiny objects, a breakthrough that could lead to devices that can perform surgery, a new study says.

The joints of these so-called microgrippers clench when exposed to cues such as chemicals or high temperatures, allowing the devices to grasp objects.

In the new research, the devices were used to pick up a bead and remove living cells at the end of a vein-like tube, similar to a biopsy in humans.

In the old days, large cuts were the only ways a surgeon could access an organ. Today, doctors can sometimes operate using small incisions and tiny, tethered tools such as microgrippers.

Now the "ultimate vision [is] a small machine that can be swallowed or injected that can perform the same function and reduce the invasiveness, so you don't have to cut," said study author David Gracias, a chemical and biomolecular engineer at Johns Hopkins University in Baltimore, Maryland.

But Gracias and others caution that such medical advances are still many years down the road.

Quantum Leap

The microgrippers' design—six three-jointed digits attached to a "palm"—was inspired by crabs.

When exposed to certain chemicals or a temperature greater than 104 degrees Fahrenheit (40 degrees Celsius)—about the temperature of a human with a moderate-to-high fever—a polymer in the joints softens and makes the fingers spring shut.

Conventional microgrippers are usually attached to wires and triggered with mechanical or electrical signals—limiting the machines' mobility.

But the new device could be maneuvered through the body by moving a simple bar magnet above the skin, Gracias said.

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