According to researchers at Rice University, fibers made of carbon nanotubes configured as wireless antennas perform as well as copper antennas but are 20 times lighter. The antennas may offer practical advantages for aerospace applications and wearable electronics where weight and flexibility are factors.
The discovery offers more potential applications for the strong, lightweight nanotube fibers developed by chemical engineer Matteo Pasquali in the Rice lab. The lab introduced the first practical method for making high-conductivity carbon nanotube fibers in 2013 and has since tested them for use as brain implants and in heart surgeries, among other applications.
The research could help engineers who seek to streamline materials for airplanes and spacecraft where weight equals cost. Increased interest in wearables like wrist-worn health monitors and clothing with embedded electronics could benefit from strong, flexible and conductive fiber antennas that send and receive signals.
The Rice team and colleagues at the National Institute of Standards and Technology (NIST) developed a metric they called “specific radiation efficiency” to judge how well nanotube fibers radiated signals at the common wireless communication frequencies of 1 and 2.4 GHz and compared their results with standard copper antennas. They made thread comprising from eight to 128 fibers that are about as thin as a human hair and cut to the same length to test on a custom rig that made straightforward comparisons with copper practical.
Contrary to earlier results by other labs (which used different carbon nanotube fiber sources), the Rice researchers found the fiber antennas matched copper for radiation efficiency at the same frequencies and diameters. Their results support theories that predicted the performance of nanotube antennas would scale with the density and conductivity of the fiber.
Researchers got the same performance as copper for the same diameter and cross-sectional area, but once they took the weight into account, they found that they are basically doing this for 1/20th the weight of copper wire. Although manufacturers could simply use thinner copper wires instead of the 30-gauge wires they currently use but those wires would be very fragile and difficult to handle.
