ILL EFFECTS OF CARBON NANOTUBE

Excerpt: Inhaled carbon nanotubes accumulate within cells at the pleural lining of the lung as visualized by light microscopy.

Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems. Now a collaborative study from North Carolina State University, The Hamner Institutes for Health Sciences, and the National Institute of Environmental Health Sciences shows that inhaling these nanotubes can affect the outer lining of the lung, though the effects of long-term exposure remain unclear.

Using mice in an animal model study, the researchers set out to determine what happens when multi-walled carbon nanotubes are inhaled. Specifically, researchers wanted to determine whether the nanotubes would be able to reach the pleura, which is the tissue that lines the outside of the lungs and is affected by exposure to certain types of asbestos fibers which cause the cancer mesothelioma. The researchers used inhalation exposure and found that inhaled nanotubes do reach the pleura and cause health effects.

Short-term studies do not allow conclusions about long-term responses such as cancer. However, the inhaled nanotubes "clearly reach the target tissue for mesothelioma and cause a unique pathologic reaction on the surface of the pleura, and caused fibrosis," says Dr. James Bonner, associate professor of environmental and molecular toxicology at NC State and senior author of the study. The "unique reaction" began within one day of inhalation of the nanotubes, when clusters of immune cells (lymphocytes and monocytes) began collecting on the surface of the pleura. Localized fibrosis, or scarring on parts of the pleural surface that is also found with asbestos exposure, began two weeks after inhalation.

The study showed the immune response and fibrosis disappeared within three months of exposure. However, this study used only a single exposure to the nanotubes. "It remains unclear whether the pleura could recover from chronic, or repeated, exposures," Bonner says. "More work needs to be done in that area and it is completely unknown at this point whether inhaled carbon nanotubes will prove to be carcinogenic in the lungs or in the pleural lining."

The mice received a single inhalation exposure of six hours as part of the study, and the effects on the pleura were only evident at the highest dose used by the researchers - 30 milligrams per cubic meter (mg/m3). The researchers found no health effects in the mice exposed to the lower dose of one mg/m3.

ELECTRONICS USING LIGHT

In any electronics circuit, we can see wide range of elements that are operating using electric circuitries. Each of them has different functionalities, such as inductors, capacitors, resistors, transistors and so forth. Scientists believe that if anyhow these elements could bring down to nanoscale level they could be operated with light instead of electricity.

Engheta, a scientist at the University of Pennsylvania, along with Andrea Alů, believe that it is possible to create a nanoscale circuit board that has the potential to be useful in communications.

According to them, going to them has three advantages:

1. Further miniaturization would ensure more compactness and smaller volume.

2. Using optical communication would provide more bandwidth.

3. Less energy requirement.

Though researchers have tried computer simulation to test their ideas related to nanoscale circuit boards, experimental realization of their theories with a proof of concept for lumped circuit elements is still to be done. They are thinking of constructing of nanowires to suit their purpose and to fabricate lumped optical circuit elements.

Once a proof of concept is realized for this circuit board, Engheta hopes to take optical nanocommunications to another level. “We are extending our concept to other elements that are non-linear,” he says. “This could allow us to develop switches, opening the door to computation.”

LIGHT AND SOUND VIBRATIONS TOGETHER IN NANOCRYSTAL

For the first time, researchers at the California Institute of Technology (Caltech) have created a nanoscale crystal device that permits scientists to confine both light and sound vibrations in the small space together.

Generally light and sound waves can be manipulated separately; but it is the first time that it is possible to accommodate and create the interaction between within a nanocrystal which is a single structure.

Mechanical vibrations, with frequencies as high as tens of gigahertz, can be produced due to the interactions between sound and light in this tiny device. This awesome facility will provide the ability of nanocrystals to send the large amount of information. In light wave communication system, where we need to achieve high frequencies, this device can give us a suitable option to fasten the speed of data transfer. In biosensor and nanomechanics, it can also serve us some useful purpose.

All of the above said techniques can be incorporated into a single silicon microchip.

In these types of crystals, two types of basic units are present: quanta of light and quanta of sound. Therefore researchers got the ability to manipulate sound and light in same nanoplatform and to interconvert the energy between two systems. So scientists got the ability to engineer this property in many ways.

As the light and sound waves are confined in small space, the interactions of the light and sound get stronger as the volume to which they are confined decreases. Second, the amount of mass that has to move to create the sound wave gets smaller as the volume decreases.

Researchers pointed out that, in addition to measuring high-frequency sound waves, it's actually possible to produce these waves using only light. Light waves can be converted into microwave-frequency sound waves on the surface of a silicon microchip.

These sound waves are analogous to the light waves of a laser. The way the system has been designed that makes it possible to use these sound waves by routing them around on the chip, and making them interact with other on-chip systems. Essentially, optomechanical crystals provide a whole new on-chip architecture in which light can generate, interact with, and detect high-frequency sound waves.