Long Term Implantable Bio-Sensors Developed Using Carbon Nanotubes

Using carbon nanotubes, scientists have developed a biosensor that can be implanted under the skin that will last more than a year. They have also developed a short term biosensor that can travel through the blood stream flowing through the different organs of the body without causing damage.

In order to get a reading and collect data from the sensors, a laser that produces near-infrared light is used to detect the fluorescent signal off of the nanotube based devices.

The long term biosensor was made to detect nitric oxide (NO) levels in the body for monitoring cancerous cells. This is the first time that implantable nanosensors could be used within the body for this extended period of time.

For the biosensor to last under the skin, it is embedded in a gel made from a polymer called alginate for protection.

This application is not limited to NO detection, it can also be used to detect glucose (blood sugar) levels in the body for monitoring diabetes.

Imaging Individual Molecules Possible Through Magnetic Resonance Imaging and Carbon Nanotubes

Scientists are looking into imaging of individual molecules by using carbon nanotubes and magnetic resonance imaging (MRI). MRI is an imaging technology that uses magnets and radiowaves to construct an internal 3D image of the target.

Graphene is a one atom thick layer of carbon atoms and is considered a 2 dimensional object. The structure of graphene resembles that of chicken wire. When it is rolled up to form a cylinder, it is called a carbon nanotube.

Graphene is one of the strongest material around and is also the thinnest. It also conducts electricity efficiently and is a very good conductor of heat. Graphene is almost completely transparent, yet so dense that even the smallest atom helium cannot pass through it.

Carbon nanotubes also retain these properties and are used in different technologies such as nanotechnology, material science, electronics, and even in bionanotechnology.

Damaged and Impure Carbon Nanotubes Provide Attractive, Low-cost Alternative Catalysts In Fuel Cells.

This drawing shows a double-walled carbon nanotube. Each tube is made of a rolled-up sheet of carbon that’s one-atom thick.
Credit: Guosong Hong

A carbon nanotube is a tiny cylinder that is one atom thick. The structure is made up of a single layer of carbon atoms that are rolled up to form the cylinder. These single layer carbon atom structure is graphene. Graphene has been touted as the "wonder" material of the 21st century.

There are many techniques to produce carbon nanotubes, two of them are by Arc-discharge and Chemical vapor deposition (CVD).

With arc-discharge, a chamber is filled with non-reactive gas. Two rods of graphite are placed in the chamber; one is an anode, the other the cathode. A current is run through the rods to produce a spark. The spark vaporizes the tip of the rods and carbon gas is released. On the cathode, carbon nanotubes are formed.

CVD is done by using carbon based gas and a metal catalyst particle. A non reactive gas is passed through the heated carbon gas. This is then passed through a furnace that's heated up to 1150 C. Nanotubes form at the tubes in the furnace and is then collected.

CVD is the most promising in terms of commercial production but research is still ongoing to find the most efficient way to produce carbon nanotubes.

'Unzipped' carbon nanotubes could help energize fuel cells and batteries, Stanford scientists say

Multi-walled carbon nanotubes riddled with defects and impurities on the outside could replace some of the expensive platinum catalysts used in fuel cells and metal-air batteries, according to scientists at Stanford University. Their findings are published in the May 27 online edition of the journal Nature Nanotechnology.

"Platinum is very expensive and thus impractical for large-scale commercialization," said Hongjie Dai, a professor of chemistry at Stanford and co-author of the study. "Developing a low-cost alternative has been a major research goal for several decades."