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August 03, 2010

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Micro-motors would fit to swim human arteries

Jan. 20, 2009
Courtesy Monash Univeristy
and World Science staff

Many com­plex sur­geries for stroke, hard­ened ar­ter­ies or blood ves­sel block­ages are about to be­come safer as re­search­ers fi­nal­ize the de­sign of micro-mo­tors small enough for in­jec­tion in­to the blood­stream, sci­en­tists say.

A pa­per pub­lished Jan. 20 in the Jour­nal of Mi­crome­chan­ics and Mi­cro­engi­neer­ing de­tails how re­search­ers are har­ness­ing piezo­elec­tricity—the en­er­gy force most com­monly used to trigger-start a gas stove—to pro­duce “mi­crobot mo­tors” a fourth of a mil­li­me­tre wide.

The re­mote-controlled robots, small enough to swim up ar­ter­ies, are designed to save lives by reach­ing re­mote parts of the blood­stream with­out dis­rupt­ing del­i­cate tis­sues. With sen­sor equip­ment at­tached to the mi­crobot mo­tor, a sur­geon’s view of, say, an ar­tery could be en­hanced; it’s al­so hoped that the abil­ity to work re­motely would in­crease the sur­geon’s dex­ter­ity.

Mo­tors have lagged be­hind in the age of tech­no­log­i­cal minia­turisa­t­ion and they pro­vide the key to mak­ing robots small enough for the blood­stream, said James Friend, lead­er of the re­search team at Aus­trali­a’s Monash Uni­ver­s­ity.

“If you pick up an elec­tron­ics cat­a­logue, you’ll find all sorts of sen­sors, LEDs, mem­o­ry chips, etc. that rep­re­sent the lat­est in tech­nol­o­gy and minia­turisa­t­ion,” he said. But take a look at the mo­tors “and there are few changes from the mo­tors avail­a­ble in the 1950s.”

Friend and col­leagues be­gan their re­search over two years ago in the be­lief that piezo­elec­tricity was the best en­er­gy force for micro-mo­tors be­cause the en­gines can be scaled down while re­main­ing force­ful enough, even at the sizes nec­es­sary to en­ter the blood­stream, for mo­tors to swim against the blood’s cur­rent and reach spots dif­fi­cult to op­er­ate up­on.

Piezo­elec­tricity is most com­monly found in quartz watches and gas stoves. It’s based on the abil­ity of some ma­te­ri­als to gen­er­ate elec­tric po­ten­tial, en­a­bling a flow of cur­rent, in re­sponse to me­chan­i­cal stress.

In the case of a gas stove, the ig­ni­tion switch on a stove trig­gers a spring to re­lease a ball that smashes against a piece of piezo­elec­tric ma­te­ri­al, of­ten kinds of crys­tal, which trans­lates the force of the ball in­to more than 10,000 volts of elec­tricity which then trav­els down wires, reaches the gas, and starts the stove fire. 

Piezo­elec­tric de­signs “have fa­vour­a­ble scal­ing char­ac­ter­is­tics and, in gen­er­al, are sim­ple,” Friend said. The team has pro­duced pro­to­types of the mo­tors and is now work­ing on ways to im­prove the as­sembly meth­od and the me­chan­i­cal de­vice that con­trols the micro-mo­tors, he added.

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Many complex surgies for stroke, hardened arteries or blood vessel blockages are about to become safer as researchers finalize the design of micro-motors small enough for injection into the bloodstream, scientists say. A paper published Jan. 20 in the Journal of Micromechanics and Microengineering details how researchers are harnessing piezoelectricity—the energy force most commonly used to trigger-start a gas stove—to produce “microbot motors” a fourth of a millimetre wide. The remote-controlled robots are small enough to swim up arteries could save lives by reaching remote parts of the bloodstream without violating delicate tissues. With sensor equipment attached to the microbot motor, a surgeon’s view of, say, an artery could be enhanced; it’s also hoped that the ability to work remotely would increase the surgeon’s dexterity. Motors have lagged behind in the age of technological miniaturisation and provide the key to making robots small enough for the bloodstream, said James Friend, leader of the research team at Australia’s Monash University. “If you pick up an electronics catalogue, you’ll find all sorts of sensors, LEDs, memory chips, etc. that represent the latest in technology and miniaturisation. Take a look however at the motors and there are few changes from the motors available in the 1950s,” he remarked. Friend and colleagues began their research over two years ago in the belief that piezoelectricity was the best energy force for micro-motors because the engines can be scaled down while remaining forceful enough, even at the sizes necessary to enter the bloodstream, for motors to swim against the blood’s current and reach spots difficult to operate upon. Piezoelectricity is most commonly found in quartz watches and gas stoves. It’s based on the ability of some materials to generate electric potential, enabling a flow of current, in response to mechanical stress. In the case of a gas stove, the ignition switch on a stove triggers a spring to release a ball that smashes against a piece of piezoelectric material, often kinds of crystal, which translates the force of the ball into more than 10,000 volts of electricity which then travels down wires, reaches the gas, and starts the stove fire. “Opportunities for micro-motors abound in fields as diverse as biomedicine, electronics, aeronautics and the automotive industry. Responses to this need have been just as diverse, with designs developed using electromagnetic, electrostatic, thermal and osmotic driving forces,” Friend said. “Piezoelectric designs however have favourable scaling characteristics and, in general, are simple designs, which have provided an excellent platform for the development of micro-motors.” The team has produced prototypes of the motors and is now working on ways to improve the assembly method and the mechanical device which moves and controls the micro-motors, he added.