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“Fantastic Voyage”-inspired Chip Is Made To Move

Stanford researchers present a way to move chips through the body using magnetic fields

2 min read
“Fantastic Voyage”-inspired Chip Is Made To Move

For a number of basic physics reasons, the world of the 1960’s movie Fantastic Voyage will always remain out of reach. We won’t ever shrink humans and submarines down to microscopic sizes to perform medical interventions inside the human body.

But hasn’t stopped researchers from attempting to develop devices that could do much the same thing. Some have opted for pills that propel themselves with mechanical parts, like jarringly sharp insect-inspired legs or moving clamps that perform an inchworm crawl. Others are exploring more passive schemes that use magnetic fields to guide ferromagnetic objects through the bloodstream.

A team led by Ada Poon of Stanford University has devised a different approach. After convincing themselves that ultra-small wireless antennas can receive a fair amount of power even after transmissions pass through human tissue, Poon and colleagues built a 3 mm x 4 mm prototype chip that exploits an external magnetic field to actively propel and steer itself.

The chip harnesses the Lorentz force, the force that arises when an electric charge moves in a magnetic field. One scheme (illustrated above) uses electrodes at the rear of the chip to run a current through a fluid. The other uses a loop of wire attached to the chip. Alternating the direction of current in the loop will allow the chip to wiggle itself forward by virtue of asymmetric drag.

Experimenting in water, Poon’s team found they could propel the chip at speeds of 0.53 centimeters per second with a magnetic field that’s about 1% as strong as the field in an MRI. Stanford graduate student Anatoly Yakovlev presented the chip designs on Tuesday at the IEEE International Solid-State Circuits Conference in San Francisco, Calif.

Poon says this approach to locomotion requires less energy and will be easier to miniaturize than mechanical locomotion. And unlike approaches that use passive magnetic materials, Poon says her team's current propulsion schemes shouldn’t need strong or complex magnetic fields to work. At its present size, she says the chip is suitable for the stomach or digestive track and perhaps the larger vessels of the body’s venous system.

Attendees of Yakovlev’s talk brought up a few safety concerns, including the possibility that the chip’s electrodes could create unwanted chemical reactions. But Poon says careful selection of electrode materials will cut down on that risk and that the biggest foreseeable danger is that the device might get lost as it’s guided through the body. This is unlikely to be much of an issue in the digestive system, but “for motion through the blood stream, the danger is much higher because the device must be removed after use,” Poon says. She says adding feedback control to the chip to assist with navigation might help prevent an operator from losing the device.

Poon says that it should be fairly straightforward to shrink down the device and lists drug delivery and diagnostic imaging and sensing as potential applications. But we’re still a far way from Richard Feynman’s “swallow the surgeon” vision of the future or even in vivo tests of the device. In the short term, Poon says the locomotion schemes the team has devised could help improve existing medical equipment, by, for example, helping guide the tips of catheters used in cardiovascular surgery.

Image courtesy of Ada Poon

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A photo showing machinery in a lab

Foundries such as the Edinburgh Genome Foundry assemble fragments of synthetic DNA and send them to labs for testing in cells.

Edinburgh Genome Foundry, University of Edinburgh

In the next decade, medical science may finally advance cures for some of the most complex diseases that plague humanity. Many diseases are caused by mutations in the human genome, which can either be inherited from our parents (such as in cystic fibrosis), or acquired during life, such as most types of cancer. For some of these conditions, medical researchers have identified the exact mutations that lead to disease; but in many more, they're still seeking answers. And without understanding the cause of a problem, it's pretty tough to find a cure.

We believe that a key enabling technology in this quest is a computer-aided design (CAD) program for genome editing, which our organization is launching this week at the Genome Project-write (GP-write) conference.

With this CAD program, medical researchers will be able to quickly design hundreds of different genomes with any combination of mutations and send the genetic code to a company that manufactures strings of DNA. Those fragments of synthesized DNA can then be sent to a foundry for assembly, and finally to a lab where the designed genomes can be tested in cells. Based on how the cells grow, researchers can use the CAD program to iterate with a new batch of redesigned genomes, sharing data for collaborative efforts. Enabling fast redesign of thousands of variants can only be achieved through automation; at that scale, researchers just might identify the combinations of mutations that are causing genetic diseases. This is the first critical R&D step toward finding cures.

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