February R&D Round Up

E-mail Melanie Martella

Ah, February, shortest of months and yet simultaneously the winter month that seems the longest. To cheer you up (or at least intrigue and educate you), this month's sensor developments include novel materials to get rid of biofilms, nanotubes to the rescue for making optical power measurements, and spray-on organic electronics to boost the light sensitivity of CMOS image sensors.

Biofilms Beware
Biofilms, those strange guck-like layers that form on ship hulls or, really, anything that sits in water for any length of time, are unwanted, to put it mildly. Biofilm build-up on ship hulls slows them down (and can attract barnacles and other aquatic beasties who then attach themselves to the vessel—picture the Flying Dutchman's ship and crew from the Pirates of the Caribbean movies). People who put sensors and other devices into the water don't like them because they can prevent the devices from working properly by gumming up the works. So, preventing biofilms from getting a foothold is a very desirable thing. Researchers from Duke University's Pratt School of Engineering have come up with a new material that can help. As described in the article, "Novel Materials Shake Ship Scum" the material wrinkles its surface when a stimulus—an electrical signal, pressure, being stretched—is applied, dislodging any bacteria or other undesirables.

Carbon Nanotubes for Optical Power Measurement
Carbon nanotubes are very versatile, which explains the sheer number and variety of research projects that use them. Now they can be used to measure the absolute power produced by lasers, particularly those used in optical telecommunications. NIST's new chip-scale cryogenic radiometer, as described in "NIST's 'Nanotubes on a Chip' May Simplify Optical Power Measurements", incorporates circular patches of vertically-aligned carbon nanotubes (VANTAs) grown on a micromachined silicon chip to create a tiny, highly-efficient, and accurate optical power detector. The VANTAs act, variously, as the different components required for the radiometer to function, in this case as an electrical heater and a thermistor. The chip-scale device does not have to hand assembled and is smaller, easier to make, and can be more readily adjusted than the traditional devices.

Plastics for More Light-Sensitive Cameras
The future of image sensors just got rather more interesting. Researchers at the Technische Universität München (TUM) have discovered that they can improve the sensors' light sensitivity by spray-coating CMOS image sensor chips with a very thin film of electrically conductive plastic. The plastic film is far more light-sensitive than the traditional silicon CMOS sensors. The article, "Image sensors out of a spray can" describes the research in more detail and points out that, by altering the properties of the organic compound used to coat the chips, this technique could lead to low-cost IR sensors.