In the 1966 science fiction classic "Fantastic Voyage," a tiny submarine with a crew of five is miniaturized and injected into a comatose man to surgically laser a blood clot in his brain and save his life.
At this week's American Chemical Society Nanoengineering expert Joseph Wang detailed his latest work in developing micromotors and microrockets that are so small that thousands would fit inside this "o" that could bring new medical and industrial applications.
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Such machines could someday perform microsurgery, clean clogged arteries or transport drugs to the right place in the body. But there are also possible uses in cleaning up oil spills, monitoring industrial processes and in national security, Wang said.
"We have developed the first self-propelled micromotors and microrockets that use the surrounding natural environment as a source of fuel," Wang said in a statement. "The stomach, for instance, has a strongly acid environment that helps digest food. Some of our microrockets use that acid as fuel, producing bubbles of hydrogen gas for thrust and propulsion. The use of biocompatible fuels is attractive for avoiding damage to healthy tissue in the body."
Fuel and propulsion systems have been a major barrier in moving science fiction closer to practical reality, Wang said. Some micromotors and even-smaller nanomotors have relied on hydrogen peroxide fuel, which could damage body cells. Others have needed complex magnetic or electronic gear to guide their movement.
Wang's University of California, San Diego lab has developed two types of self-propelled vehicles - microrockets made of zinc and micromotors made of aluminum. The lab has developed what it calls a tubular zinc micromotor, which is one of the world's fastest, able to move 100 times its 0.0004-inch length in just one second. That's like a sprinter running 400 miles per hour, said Wei Gao, a graduate student in the lab. The zinc lining is biocompatible. It reacts with the hydrochloric acid in the stomach, which consists of hydrogen and chloride ions. It releases the hydrogen gas as a stream of tiny bubbles, which propel the motor forward. "This rocket would be ideal to deliver drugs or to capture diseased cells in the stomach," said Gao.
The newest vehicles are first-of-their-kind aluminum micromotors. One type, which also contains gallium, uses water as a fuel. It splits water to generate hydrogen bubbles, which move the motor. "About 70% of the human body is water, so this would be an ideal fuel for vehicles with medical uses, such as microsurgery. They also could have uses in clinical diagnostic tests, in the environment and in security applications," Gao stated.
Another development - an aluminum micromotor -- doesn't have gallium and is the first such motor that can use multiple fuels -- acids, bases and hydrogen peroxide, depending upon its surroundings, opening it up for use many more environments than ever before, Gao noted.
According to a Wikipedia entry, Wang has long led development of biosensors, bioelectronics and nanotechnology. Wang's work in the field of nanomachines, involving novel motor designs and applications, has led to the world fastest nanomotor, to a novel motion-based DNA biosensing, and nanomachine-enabled isolation of biological targets, such as cancer-cell isolation and to advanced motion control in the nanoscale. He has also pioneered the use of body-worn printed flexible electrochemical sensors including textile and tattoo biosensors.
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