This month we have a special antenna that helps robotic submarines to stay in touch with their handlers, a self-powered nanoscale sensor, and a novel MEMS sensor that can measure the shear stress generated by turbulent flows.
Antennas Aweigh
There's quite a bit of interest in using small robotic submarines these days. Oceanographers want them to for research purposes, countries and oil and gas companies want them for resource exploration, and the military wants them for surveillance, repair, and monitoring uses. Unfortunately, water is a very poor transmission medium for radio waves which means that these devices have difficulty transmitting messages to their handlers or receiving GPS signals unless they pop up to the surface. Mechanical engineer Jake Piskura of Brook Ocean Technology, funded by the U.S. Office of Navy Research, took miniaturized GPS and communications chips and created a small tethered antenna that piggybacks on the submarine but can ascend to the ocean surface to maintain communications and receive GPS signals for location, leaving the submarine itself submerged. (You can read more in the article "Tethered antenna keeps subs in touch," at New Scientist.)
Self-Powered Nanosensors
Zhong Lin Wang, Regents professor in the School of Materials Science and Engineering at the Georgia Institute of Technology, and his collaborators have been very busy with zinc oxide nanowires. The nanowires turn out to be piezoelectric—when mechanically stressed they produce an electrical charge. The researchers have created nanogenerators, arrays of zinc oxide nanowires, that can generate 1.2 V for a strain rate of <2%/s. By coupling nanogenerators with a tiny pH sensor and a UV sensor, they've developed tiny self-powered nanosensors. For far more technical detail, I'll refer you to the Georgia Tech news release, "Improved Nanogenerators Power Sensors Based on Nanowires."
Tiny Sensor for Turbulent Flows
Vijay Chandrasekharan of the University of Florida has created a tiny MEMS-based sensor that can measure the shear stress generated as turbulent flows pass over a surface—a boon for anyone interested in reducing the shear stress experienced by an aircraft. The research was the result of a NASA Research Announcement (NRA) study contract awarded by the Subsonic Fixed Wing Project of NASA's Aeronautics Research Mission Directorate. Dr. Mark Sheplak, of the Department of Mechanical and Aerospace Engineering at the University of Florida was the NRA's principal investigator. As detailed in the article "The Sheer Delight of Tackling Shear Stress," the sensor has already been used to characterize wind tunnels and is notable for both its small size and its ability to measure a far greater range of shear stress than was possible with existing sensors. Work is already underway to develop a wireless version of the device.