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.

For instance, the highly mobile machines could capture and retrieve objects in hard-to-reach spots, such as inside capillaries.

The minuscule gadgets are also relatively inexpensive and can be mass-produced, added Gracias, whose research appeared earlier this month in the journal Proceedings of the National Academy of Science.

Mauro Ferrari, deputy chairperson of the Department of Biomedical Engineering at the University of Texas Health Science Center in Houston, called the new study a "quantum leap."

"It is a very clever idea. You can find some foundations in the work of many labs over the years," said Ferrari, who was not involved in the research.


However, major obstacles must be scaled before wireless microgrippers hit doctors' offices.

For one, the device can become lost in the body, or lodged in tissue.

That could be remedied if the tool could be made to move on its own, without the aid of a magnet—a major goal of Gracias and his team.

Likewise, in the body the gripper can only grab a target once and cannot be instructed to release tissue and grab another piece. This could get complicated if the device grabs onto the wrong object in a body, said Ferrari of the University of Texas.

The ability to biologically activate small tools is a "wonderful notion," but getting from this point to a clinical application is 10 to 15 years away, Ferrari cautioned.

Using the wireless microgrippers to reach now inaccessible parts of the brain to close aneurysms may be a more practical use, Ferrari added.

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