Swallow-the-Surgeon medical care relies on a three by four millimeter-sized submersible that navigates the bloodstream to deliver drugs and perform minor surgical procedures such as cleaning arteries. (Source: Stanford)
Edgar Albert Guest said "It couldn't be done" in the opening line of his 1916 poem by that name, but his point was to encourage inventors to seek supposedly unattainable goals, as indicated in the last line of his poem where he advises to just "tackle the thing that 'couldn’t be done,' and you’ll do it."
Electrical engineer Ada Poon recently took Guest's advice when she bucked conventional wisdom by suggesting that high-frequency radio waves could power tiny submersibles while they navigate the bloodstream to perform diagnostics, deliver payloads (drugs), and even perform minor surgical procedures such as dissolving blood clots or removing a blockage from sclerotic arteries.
Poon's research team at Stanford University recently showed prototypes of its "swallow-the-surgeon" submersibles that can swim through the blood stream at the International Solid-State Circuits Conference (ISSCC 2012, Feb 20-24, San Francisco, Calif.)
The self-propelled medical submersible measures just three millimeters wide by four millimeters long, small enough to be injected into the body where it can be directed by wireless power beams.
Today's medical implants require batteries, which often take up half the volume of the device. Usually these batteries must be periodically replaced, but even those that are rechargeable through the skin are too bulky to fit inside a millimeter-sized submersible.
Engineers before Poon also said "it couldn't be done" because even if a millimeter sized battery could be made, the muscle, fat, and bones of the body were electrical conductors and would hence block high-frequency power beams. Poon, however, was not cowed by convention, but instead explored modeling human tissue as a low-loss dielectric, resulting in millimeter sized antennas that have proven sensitive enough to gather the energy needed to power very small submersibles. Poon now maintains that a one gigahertz power beam can convey 100-times more energy than engineers had previously assumed, making self-propelled medical devices feasible.
Poon's demonstration at ISSCC showed how millimeter-sized submersibles could be powered by radio beams along with their on-board electronics. The antenna on the prototype measured just two millimeters square. Two types of motors were shown by Poon--one that used alternating current to create a swishing motion similar to a kayaker going upstream, and a second that uses direct current to propel fluid through the device to push it forward. The highest attainable speed so far is five millimeters per second.
Poon's team included Stanford doctoral candidates Daniel Pivonka and Anatoly Yakovlev. Funding was provided by C2S2 Focus Center, Olympus Corporation and Taiwan Semiconductor Manufacturing Company.
