The monitoring of air quality can be a tricky business. Gases may be blown into the sampling site from another area, they may leak out of an air sample before it can be analyzed, or the sampling container itself may introduce compounds, emitted through off-gassing. If samples are being gathered in remote areas, it can also be difficult getting bulky equipment to and from the sampling site. Now, scientists from Sandia National Laboratories have announced a tiny new type of air sampler, that addresses these and other challenges.
Each sampling container is only about the size of an earplug, and incorporates a chamber made from commonly-available alumina alloy, that is topped with a tough, inexpensive micro-valve. An electric pulse (provided by an external source) causes that valve to open, drawing the necessary volume of air into the chamber within a few seconds, through an opening with a diameter close to that of three human hairs.
A tiny hotplate built into the top of the chamber then heats the alloy adjacent to that opening. Because alumina is a type of solder, it liquefies, filling in the opening. Once the melted solder cools and resolidifies, the air is sealed inside the chamber. It can stay in there indefinitely, until the sampler is opened at a laboratory for analysis. The alloy doesn’t off-gas at all, so the sample inside the chamber should remain uncorrupted.
Because the air samplers are so small, simple and light, the researchers say that they could be put in locations that larger, traditional samplers could not. This means that they could perhaps be mounted on unmanned aerial vehicles, or slung beneath atmospheric balloons. Conversely, geologists could also lower them into the earth through narrow bore holes, physicians could use them to gather patients’ breath samples, and soldiers could use them to detect toxic gases on the battlefield.
First and foremost, however, the samplers may to be put to work in a study of greenhouse gases. A plan has been proposed to send batches of 100 of the samplers into the atmosphere on board tethered, unmanned blimps in a remote region of Alaska. There, they will gather sample particles around which cloud droplets form, in order to corroborate air pollution data gathered by NASA satellites.
A paper on the research was recently published in the journal Review of Scientific Instruments.
Source: Sandia National Laboratories
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