Microgripper Can Harvest “Microbiopsies” Via Minimally Invasive Surgery

Pathologists may eventually have a new tool that makes it possible to collect microbiopsies using minimally-invasive surgery. The invention is a product of research at Johns Hopkins University and uses biochemicals to operate the device. A tiny handlike gripper is 500 micrometers (0.05 centimeters) in diameter, and made of a film of copper and chromium covered with polymer. Scientists say the gripper can grasp tissue or cell samples inside the body.

As a proof of concept, researchers used the device to perform an in vitro biopsy on a cow’s bladder. The technology also might work in clinical labs, the researchers said. The device can be moved remotely by using a magnet. It has “fingers” that will close around the target object in response to chemical triggers.

An article in MIT’s Technology Review explained how it works. The gripper remains open if the polymer stays rigid. Researchers can activate the gripper’s fingers to make them curl inward to form a ball that is 190 micrometers wide by adding a chemical trigger or lowering the temperature, thus softening the polymer. Adding a second chemical sends a signal to reopen the gripper. The chemicals used as triggers are harmless to humans.

For clinical labs, these microgrippers could be used for lab-on-a-chip applications, the article said. The microgrippers could move samples around a chip or clean debris. One drawback, however, is that using chemical triggers can make the device difficult to control. If the chemical environment changes, it can change how the device performs.

The lead researcher is David Gracias, Ph.D., a biomolecular- and chemical-engineering professor at Johns Hopkins University. During a meeting of the American Chemical Society earlier this year, Gracias and colleagues demonstrated how the microgripper could grasp and maneuver tiny beads and clumps of cells in a petri dish.

Researchers believe the technology is a step toward surgical tools that move freely inside the human body. The gripper would respond autonomously to chemical cues in the body, and could, for example, react to the biochemicals released by infected tissue. The microgripper could close around the tissue, so that doctors could remove the pieces for analysis, the article said.

“This is the first mobile micromachine that has been shown convincingly to do very useful things,” Gracias says. “And it does not require electric power for operation. We want to make mobile surgical tools. The ultimate goal is to have a machine that you can swallow, or inject small structures that move and can do things.”

Although introduction of this tool for microsurgery is likely to be years away, it is a demonstration of micro-technologies and nano-technologies that have the potential to give pathologists new capabilities. This invention is also consistent with the trend to perform laboratory tests with smaller specimens.