Medical researchers would like to use nano-scale tubes to push very tiny amounts of drugs dissolved in water to exactly where they are needed in the human body. The roadblock to putting this theory into practical use has been the challenge of building pumps small enough to do the job. In addition to the engineering challenge of building a nano-scale pump, there is the added complication of clogging by any biological molecule that can occur in valves small enough to fit a channel the size of bacteria.
The solution – discovered by researchers at Arizona State University – is to create a system that does not rely on mechanical parts.
The ASU team of scientists and engineers reports in the American Chemical Society journal Langmuir (Thursday, August 29, 2002) on a technique they developed to pull water up a tube tinier than a straw by shining a beam of light on the surface of the tube. This technological advance, referred to as photocapillarity, may one day find a use in nanotechnology applications, such as the targeted distribution of medicine in the body.
"As the size of capillaries or channels in devices shrinks, it becomes very difficult to control the movement of "liquid," says Dr. Antonio Garcia, Arizona State University Bioengineering professor. "The everyday use of mechanical valves and pumps becomes difficult in nanotechnology because making them tinier is a manufacturing challenge. Also, any real-life application would be prone to operational problems, such as clogging of the pump or valve by tiny molecules."
Garcia, and colleagues Devens Gust and Mark Hayes, professors in the ASU Department of Chemistry & Biochemistry, have combined their bioengineering and chemistry skills to build upon the research on light responsive molecules.
With proceeds from a National Science Foundation grant, the researchers found a way of attaching the molecules to the surface and structuring the surrounding surface to control the spread of water.
"When we shine light just beyond the visible range, the light responsive molecules attract water and trigger the advancement of water through the channel," says Garcia.
An added benefit to the research is the development of a science lab demonstration. By the end of the year, students and teachers can order inexpensive glass tubes prepared by the ASU researchers and a laboratory guide to exploring the phenomena.
"Our hope is that by making this lab kit available it will stimulate the creativity of the next generation of scientists and engineers who will routinely design new products using nanotechnology," Garcia says.
Materials provided by Arizona State University. Note: Content may be edited for style and length.
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