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Raman spectroscopy has been used as a laboratory tool for decades. The analytical technique has matured to the point that it can now be used out in the field, including in applications involving robotics.
While the combination of Raman spectroscopy and robotics is not widespread, there are a couple of prominent applications using this combination which are described in this article.
Detecting Chemical, Biological, and Explosive Weapons
The ability to detect and identify weaponized biological and chemical agents as well as explosives is of vital importance for safeguarding soldiers on the battlefield, counterterrorism agents in the field, and first responders.
In 2006, a team of researchers from the University of Pittsburgh and the US Army showed that a drone using Raman spectroscopy could be used to identify chemical, biological, and explosive weapons.
The use of a Raman-equipped drone has major benefits over conventional detection and identification strategies. Raman spectroscopy does not require a sample collection or the use of chemical reagents, which may be cumbersome.
Raman measurements could be also used to identify a wide variety of chemical, biological, and explosive threats with just a single measurement cycle. This approach does not require the presumption of threat, as is the case with more intrusive, deliberate testing systems.
With a Raman-equipped drone, an operator can safely guide the system to an area of interest, which limits exposure to personnel. Being able to bring the testing apparatus to target also minimizes sampling issues, such as cross-contamination, along with the difficulties related to the disposal of potentially hazardous samples.
The research team’s objective was to produce a system capable of identifying chemical, biological, and explosive agents on surfaces out in the field. In this approach, the Raman system will be examining a potential agent spectrum against the background of a non-hazardous surface.
In most real-life scenarios, the ratio of agents to other materials in the background has substantial spatial variation. This variation leads to different Raman spectra from areas on the sample itself. These variances in spectra offer enough data for the accurate processing of the information and enable the identification of agents.
The drone system uses a Raman proximity sensor that must be close to the tested surface but does not necessarily have to be touching it in order to perform an analysis. The drone has separate subsystems for its video camera, Raman laser, Raman-specific optics, spectrometer, communications, and control.
The system uses a spectra database for the identification of known substances. It is also capable of detecting an unknown agent, and then flagging it for additional analysis, particularly if the spectrum of an unknown agent closely resembles that of a known spectrum. Ideally, more and more unknown spectra can be added to the system's database.
With its ability to warn about the presence of a potential threat, this robotic Raman system can be invaluable to soldiers, law enforcement, intelligence services, and first responders.
Studying Weather with Raman-Equipped Drones
In pursuit of more accurate weather forecasting, scientists from Oregon State University have created a drone-based approach that uses Raman spectroscopy in order to track air temperature about 120 meters in the air, down to a resolution of approximately 0.01 °C.
The technique developed by the team involves sending a nanosecond laser through a fiber-optic cable that descends from a drone overhead. Most of the laser light passes through the cable, but some photons rebound inside it.
A small ratio of that scattered light goes through Raman scattering. The Oregon researchers said that the amount of scattering is strongly related to the temperature of the location on the glass struck by the photon. This association allows for high-resolution temperature measurements that can be used for all kinds of weather-related applications.
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