Dr. Feng Liu is designing devices so tiny that they could be measured in terms of merely a few atoms. Called nanostructures and nanodevices, these objects are even smaller than the wavelength of light-making them even tinier than microscopic.
One nanometer is equal to one billionth of a meter. “To give you some perspective on nanotechnology, ten atoms laid out side by side would be equal to one nanometer,” says Dr. Liu, a professor in the Department of Materials Science and Engineering.
These infinitesimal structures and devices are potentially very important to many industries. In high-tech electronics, for example, silicon nanoelectronic devices could hold far more information than current microelectronic technologies are capable of.
“The advantage of creating electronics on a nanoscale level is that not only would they be smaller than current technology, but the density would be greater, and therefore, the nanodevices would be much faster for information processing,” says Dr. Liu. Nanoelectronics could be used in computers for storing vast amounts of data.
Dr. Liu is specifically interested in designing and creating nanotubes-round or coiled structures that resemble tiny tubes, which have many potential applications.
One promising method for making nanostructures is by utilizing the scientific principle of self-assembly or self-organization, which is very common in nature. For example, the planets in the solar system self-assemble through gravitational forces, and similarly, tiny atoms arrange or order themselves through chemical bonding.
Nanotubes are made through a process called atomic layer deposition by combining together tiny, thin sheets of elements (perhaps with just a single layer of atoms), such as carbon and hydrogen. A layer of hydrogen is stretched over a smaller sheet of carbon and compressed together. When released from stretching, elastic forces take over and the carbon and hydrogen curl up into a tubelike structure.
One future application for nanotubes involves measuring the pressure inside a human organ. Current methods of measuring pressure are not accurate or sensitive enough. “Several diseases, such as glaucoma, are either related to or caused by pressure inside an organ,” Dr. Liu says. “It would be beneficial to have a way to very precisely measure organ pressure.”
Dr. Liu is collaborating with medical researchers at the U to create a nanotube-based continuous organ pressure monitor that measures the pressure at any given moment inside the body.
“This is a novel way to measure tissue pressure,” says Dr. Liu. “No one has ever used nanotubes to measure pressure before.”
In the case of glaucoma, the highly sensitive and minimally invasive nanotube would be implanted inside the eye, where it would relay electrical signals to a recording chip. Since the length of the perimeter of the nanotube is fixed, it could only bend and flatten as pressure inside the organ develops. In a normal eye, the nanotube would maintain its shape. However, in an eye with glaucoma, the pressure would build around the tiny device. The hard tube would then be squeezed until it bent into an elliptical shape, and finally, into a peanut shape. Once collapsed, the tube would become very soft and highly sensitive in measuring pressure.
When a nanotube collapses from a circle into an ellipse and finally into a dumbbell shape, Dr. Liu found that the area ratio of these two transitions makes up a new geometrical constant that is used in determining pressure. “From this constant, we can define the ratio of pressure as the nanotube transitions from one shape to another,” he says. “This helps us measure pressure.”
The nanotube device will also have other applications for testing other tissue and organs, such as in the brain and the stomach, to measure pressure and detect disease.
For further information, visit Dr. Liu’s research lab page.