Miniature sensors with self-sealing valves may advance climate studies

A news release from Sandia National Laboratories: An air sampler the size of an ear plug is expected to cheaply and easily collect atmospheric samples to improve computer climate models. “We now have an inexpensive tool for collecting pristine vapor samples in the field,” said Sandia National Laboratories researcher Ron Manginell, lead author of the cover story for the Review of Scientific Instruments, the often-cited journal of the American Institute of Physics.

The novel design employs a commonly used alloy to house an inexpensive microvalve situated above the sample chamber. Sandia ear-plug-sized samplers, with silvery microvalves and solder connectors, seemingly hang poised to sample gases relevant to climate and weather. The prototype devices actually rest on a mirror, reflecting the day’s Albuquerque weather.

When heated, the alloy — a kind of solder — melts and flows, blocking the inlet hole. When cooled, the alloy resolidifies into an impermeable block that seals the gas sample inside the inert chamber below. Low cost should make widespread distribution of these sensors possible, while the noncontaminating nature of the design helps meet stringent technical requirements.

Better data collection is important because uncertainties in fact-gathering is one reason climate models reach a variety of conclusions. Winds may blow gases toward or away from a sampling site, gas contents at any location may vary by the hour and by the season, and samples collected by containers in the field may evaporate or become corrupted before analysis in a distant laboratory. Compounding the problem are difficulties in widely distributing sensors, which can be heavy, fragile and require expensive tending by humans.

The Sandia phase-change micro-valve sensor is light, cheap, tough, inexpensive to fabricate and simple to operate. It takes in gas in seconds through a tiny hole about the diameter of three human hairs. The hole closes when a tiny, low-energy hotplate on the canister’s surface melts shut the alloy through which the hole passes, sealing it.

Because the little container doesn’t outgas internally, the trapped sample remains uncorrupted until analyzed in the laboratory. The miniature sensor’s simplicity means it could travel in unmanned aerial vehicles (UAVs) or as unmonitored cargo in atmospheric balloons. The poorest countries could afford to play a role in global climate data collection....

Image from the Sandia Labs website