PORTLAND, Ore. — Next on the frontier for micro-electromechanical systems (MEMS) is the downsizing of analytic instruments like mass spectrometers -- essentially electronic noses that can sniff out nearly any substance. The enabling technology is the world's first MEMS vacuum pump small enough to fit inside a mobile device. Invented at Honeywell to enable military micro-drones to detect chemical and biological agents, these penny-sized MEMS vacuum pumps are now poised to enter the industrial, medical and consumer markets.
Honeywell's penny-sized vacuum pump (upper right) enables handheld analytic instruments by virtue of MEMS turbine-like blades.
"What we have done is create the world's smallest vacuum pump -- a unique enabler for a whole new class of analytic instruments," Wei Yang, principal research scientist with Honeywell's ACS Labs business unit, told us. "Many people have tried to downsize analytical instruments in recent years, but the vacuum pump was the last obstacle. Previously the smallest models were brick sized and consumed 100 watts, but ours is now penny sized and uses less than one watt."
The device was invented under a contract with the Defense Advanced Research Project Agency (DARPA) for installation on micro-drones. Honeywell is hoping to market these vacuum pumps as an "add-on sense of smell" for all sorts of mobile devices -- from mass spectrometers that can determine the composition of any substance to atomic clocks that provide ultra-precise navigation services.
"One thing we are very excited about is putting these into smartphones, essentially adding a sense of smell that can sense everything from toxic chemicals to pollen to general air quality," Yang said. "They could keep a cumulative record of exposure for every person carrying one, noting when and where a user was exposed."
Today sensors are restricted to specific toxins, because they are based on chemical reactions. In fact, a different sensor is needed for each type of chemical to be sensed, making them useful for specific purposes (such as carbon monoxide or smoke detectors) but useless as general-purpose sniffers. But with a mobile mass spectrometer that detects the elements in a sample, the chemical signatures of all known toxic substances could be stored in a database and searched in real-time for the most likely match.
DARPA and others had previously downsized the components for analytic instruments like mass spectrometers. Unfortunately, these chip-sized instruments work only in a vacuum, where the sample can be isolated for analysis. By downsizing a vacuum pump to chip size, Honeywell has removed the last obstacle, opening the door to handheld sniffers that can sense almost any chemical species.
"In the coming decade, this innovation is going to usher in all types of very sophisticated instrumentation for handheld mobile platforms," Yang said.
Key to the success of the world's smallest vacuum pump was the fabrication of more than 100,000 tiny turbine blades on a centimeter-sized disk. Honeywell already had the MEMS technology to create the micron-size, turbine-like blades. In fact, it fabricates them on the same equipment as its other MEMS devices. Hundreds of such bladed disks can be manufactured on each eight-inch silicon wafer.
"Our MEMS vacuum pump follows a long legacy of Honeywell MEMS developments," Yang said. "In fact, the vacuum pump is made from silicon monolithically with the same photolithographic processes and same equipment that we use to produce our MEMS gyroscopes and flow sensors."
Each vacuum pump houses two disks -- one stationary and one rotating -- covered with 10 micron-sized, turbine-like blades (shown above). The pairs of blades face each other to create the strong suction effect necessary to evacuate a test chamber before a small sample is bled in for testing.
DARPA is already working to install Honeywell's vacuum pumps into mobile analytic instruments on micro-drones. Homeland security contractors are working to expand their sensor networks with these devices and provide first responders with handheld units. But the biggest benefit, according to Yang, will come from integrating them with consumer mobile devices like smartphones.
"With these installed in everybody's smartphones, the tracking of the chemical constituents for everything from air quality to disease control to chemical spills is possible," Yang said. "You could have instant real-time dynamic tracking of any kind of chemical species and watch it moving in real-time on a map."