MEMS and motor control are two things we cover and small vacuum pumps are often controlled by micros so it made sense to talk with Dr. Wei Yang about Honeywell’s latest technology breakthrough, a tiny micro pump (Fig. 1). We talked about how it works and where it might be employed.
Wong: You came up with a tiny micro pump. What is different about it and how does it work?
Yang: Vacuum pumps are critical components for many analytical instruments. They provide the working conditions – a vacuum—that various other kinds of sensors need to function. The problem we’ve solved is one of size. Many analytical instruments have become smaller – but they remain tethered to a vacuum pump that is the size of brick, or in many cases, the size of a small appliance, and thus need to be used inside a laboratory environment.
We have created the smallest vacuum pump in the world. What’s different about our pump is that we’ve borrowed a page from conventional turbine compressors and applied the latest silicon micro fabrication techniques to the extreme: we machined hundreds of thousands of tiny turbine blades (each only a few microns in size) and over two hundred stages onto the surface of silicon wafers (Fig. 2). When a pair of the wafers is spun against each other they create a powerful suction that creates an ultra high vacuum (UHV) in a chamber. The entire apparatus is small enough and light enough to be incorporated into hand-held field devices, or on unmanned aerial vehicles (UAV), and someday even smart phones. We think this innovation creates enormous opportunity for the further miniaturization of specialized devices.
Wong: How small can the pumps be?
Yang: Our micro vacuum pump consists of two silicon wafers – each slightly smaller than a U.S. penny -- that are attached to a small motor capable of spinning the wafers at a high speed. These pumps are already small enough and light enough to be mounted on a UAV or used in smaller, hand-held devices. But with further research we can envision even smaller, flatter vacuum pumps that could be incorporated into every day consumer technology, such as smart phones. But that’s a longer-term prospect.
Wong: What are some applications for the micro pump?
Yang: Miniaturized vacuum pumps will help to usher in the proliferation of a large class of laboratory-based instruments in industrial and consumer markets that will eventually affect every day life, and lead to new functionalities for mobile devices and for health, bio-defense and security. Some examples of this include air quality, bio-toxin and health monitoring, large gas/chemical sensor networks, unmanned aerial vehicle (UAV) applications, law enforcement and even gaming.
In its current form, this micro vacuum pump is small enough and light enough that we can attach a sensor and mount it on a UAV, which could be used to measure the presence of gases or toxins in the air, a major safety and security application. Down the road, we see the potential for developing universal gas detectors and other commercial-industrial applications. Right now most gas detectors are gas-specific – so you need a specific detector for each gas you’re measuring. With a micro vacuum pump, a single device based on mass spectrometry could be programmed with software to measure for 20 different gasses simultaneously, and the entire apparatus could be part of a portable field device, or mounted on a wall.
Longer term there are even potential consumer applications, in which even smaller and flatter vacuum pumps could be incorporated into smart phones and other mobile devices. It’s possible that someday our smart phones could also function as air quality monitors, or monitor different aspects of our health or lead to new gaming applications.
Wong: What kind of power and control requirements are there?
Yang: The power consumption depends on the rate of gas flow through the pump which varies from one application from another. It may be about a watt for a flow-through device like a gas detector, but much lower when embedded in a closed system. There are no special control requirements for the basic operation of the pump.
Wong: How did this project get started?
Yang: Miniaturizing technology has been a big focus for Honeywell for a long time. This particular project started more than four years ago, when the Defense Advanced Research Projects Agency challenged Honeywell (and two university-affiliated labs) to develop a penny-sized vacuum pump. We all took different approaches to the challenge, but ultimately succeeded. Honeywell’s was the only project that included a working prototype. Honeywell has been involved in Micro Electromechanical Systems or MEMS technology since the 1960s. So the micro vacuum pump is the latest of our MEMs innovations, which include micro pressure sensors flow sensors, semi-conductor based and uncooled IR cameras, gyroscopes and other aerospace and sensor applications.
Wong: What is the future for this innovation?
Yang: This is a break-through innovation and we believe someday it will lead to break-through applications in mobile devices, medical diagnostics and instrumentation, security, sensor networks, gas detection – and others we can’t envision right now. The key is that vacuum pumps – a critical component to other technologies – can now be made small enough to drive further miniaturization among a host of applications.
Wong: How would it work with MCU controllers, electronics?
Yang: Certain operating parameters such as RPM, pressure and drive current may be fed to a microprocessor for control and power management purposes.
Can you provide historical context for theses pumps?
Yang: Conventional turbo-molecular pumps have been around since 1950’s and have become the workhorse of modern vacuum technology today. However the turbo-molecular pump’s large size and power consumption render it unsuitable for portable applications. The initial push for miniaturization was driven by NASA’s planetary exploration programs in the early 2000’s, which resulted in Creare’s D-cell sized pump built by conventional machining. The chip-scale vacuum pump challenge arose from DARPA’s Micro Gas Analyzer program in 2007 for its micro mass spectrometer. Honeywell proposed the silicon based turbo-molecular pump concept and completed a preliminary study in 2007-2008. The computer simulation and a pilot fab run became the basis for a full program later in 2008 under which the current pump was developed.
Wong: Is there a consumer take on this?
Yang: Yes, we think with further research that vacuum pumps can be made even smaller and flatter, which would then enable them to be components in smart phones and other mobile devices. This could usher in a number of potential consumer-focused applications in the air quality, health monitoring, security and gaming segments.
Wong: Can this innovation be leveraged to create other devices and tools?
Yang: Yes, although the primary objective of this innovation is related to portable chemical/gas analysis, any devices that rely on or benefit from ultra high vacuum may take advantage of the small size of the pump to expand their scalability.
Wong: How did Honeywell become involved in this project?
Yang: This particular project started more than four years ago, when the Defense Advanced Research Projects Agency challenged Honeywell (and two university-affiliated labs) to develop a penny-sized vacuum pump. We all took different approaches to the challenge, but ultimately succeeded. Honeywell’s was the only project that included a working prototype.