In experiments that pave the way for tiny mobile surgical tools activated by heat or chemicals, Johns Hopkins University researchers have invented dust-particle-size devices that can be used to grab and remove living cells from hard-to-reach places without the need for electrical wires, tubes or batteries. Instead, the devices are actuated by thermal or biochemical signals. The mass-producible microgrippers each measure approximately one-tenth of a millimeter in diameter. In lab tests, they have been used to perform a biopsy-like procedure on animal tissue placed at the end of a narrow tube. Experiments using the devices were reported last week in the online edition of Proceedings of the National Academy of Sciences. Although the devices will require further refinement before they can be used in humans, David H. Gracias, who supervised the project, said these micro-tools represent a major engineering advance. “We’ve demonstrated tiny inexpensive tools that can be triggered en masse by nontoxic biochemicals,” said Gracias. “This is an important first step toward creating a new set of biochemically responsive and perhaps even autonomous micro- and nanoscale surgical tools that could help doctors diagnose illnesses and administer treatment in a more efficient, less invasive way.”

Today, doctors who wish to collect cells or manipulate a bit of tissue inside a patient’s body often use tethered microgrippers connected to thin wires or tubes. But these tethers can make it difficult navigate the tool through tortuous or hard-to-reach locations. To eliminate this problem, the untethered grippers devised by Gracias’ team contain gold-plated nickel, allowing them to be steered by magnets outside the body. The microgrippers are triggered to close and extricate cells from tissue when exposed to certain biochemicals or biologically relevant temperatures.” That grasping ability is rooted in the chemical composition of the joints embedded in the tiny crab-shaped device’s finger-like digits. These joints contain thin layers of chromium and copper with stress characteristics that would normally cause the digits to curl themselves closed like fingers clasping a baseball. But the researchers added a polymer resin, giving the joints rigidity to keep the fingers from closing. When the microgrippers arrive at their destination, however, the researchers raise the temperature to 40 degrees C, which softens the polymer and causes the fingers to flex shut. The Hopkins TTO has obtained a provisional U.S. patent covering the technology and is seeking international patent protection.

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Posted January 21st, 2009 under Innovation of the Week, Tech Transfer

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