An article courtesy of AVEM MOUSER

What are MEMS?

Microelectromechanical systems (MEMS), also known as microsystems technology in Europe, or micromachines in Japan, are a class of devices characterized both by their small size and the manner in which they are made. MEMS devices are considered to range in characteristic length from one millimeter down to one micron – many times smaller than the diameter of a human hair.

MEMS will often employ microscopic analogs of common mechanical parts and tools; they can have channels, holes, cantilevers, membranes, cavities, and other structures. However, MEMS parts are not machined. Instead, they are created using micro-fabrication technology similar to batch processing for integrated circuits.

The rise of MEMS

OVER THE LAST COUPLE OF DECADES, THE MARKET for Micro-Electro-Mechanical Systems (MEMS) has been rapidly expanding. While the first commercial applications for MEMS technology were pressure sensors used by the automobile and medical industries, these days MEMS has a large range of other applications spread across numerous market sectors. Many of today’s most common MEMS applications are found in consumer electronics (CE), such as smart phones, tablets, and video game systems. Additionally, a variety of other applications, including wearable electronics for the health and fitness markets, also incorporate MEMS, and as the use of these devices increases, the demand for MEMS should become even more ubiquitous.

MEMS technology are basically tiny machines: microscopic structures and devices that combine mechanical, optical, and fluidic elements with electronics. Typically smaller than a grain of sand, the size of MEMS technology devices can range from less than one micron up to several millimeters. While some MEMS devices are fairly simple structures without any moving parts, others are incredibly complex, featuring multiple moving structures integrated with microelectronics.

MEMS technology was first developed in the 1970s and early 1980s and was initially called silicon micromachining. The MEMS label was created in the ‘90s, when the U.S. Department of Defense began actively investing in the technology. The first commercial application of MEMS technology was microsensors used to detect strain in steel, and these devices were used primarily in the automobile and medical markets.

According to Dr. Michael Huff, the founder and director of the MEMS and Nanotechnology Exchange (MNX), which offers MEMS design and fabrication services, the first generation of these sensors was developed following a discovery by an employee of Bell Telephone.

“There was a gentleman at Bell Telephone Labs named Charles Smith, who saw that there is a piezoresistive effect in silicon, meaning that if you strain it, you’ll see a change in resistance,” said Huff. “Not too long after that, people started gluing pieces of silicon to steel plates as strain gauges. Later, we learned that you could do what’s called an anisotropic etching of silicon, allowing you to make thin membranes out of silicon with controlled dimensions, which were important for mechanical types of sensors such as pressure transducers.”

Following these initial discoveries, this early version of MEMS technology was further refined and adopted for commercial use in the automotive and medical industries.

“People soon realized they could put the silicon strain gauges directly into the diaphragm itself, and when that happened, these devices started hitting the market quite quickly,” said Huff. “They were used as pressure transducers for automobile applications—mainly manifold air-pressure sensing—and medical applications. When I worked for a large healthcare company, we discovered you could replace a manometer—basically a macro-scale pressure sensing device— with a silicon transducer, which are a lot cheaper and more reliable. Plus, they’re disposable, so you didn’t have to sterilize them after each use.”

Modern MEMS

Over the next few decades, the MEMS industry created myriad new versions of this miniaturized technology for use in a wide range of different sectors. While the MEMS market is currently expanding like never before, Huff believes we’ve only scratched the surface of the technology’s potential applications.

“I’ve been involved with MEMS technology for 30 years,” said Huff. “The market is growing, and it’s growing faster than the traditional IC market. The number of MEMS applications out there is phenomenally large, and I think right now we’re just touching the tip of the iceberg of what’s possible.” The two major categories of MEMS devices include microsensors and microactuators. Microsensors, such as accelerometers and gyroscopes, detect information from the local environment. Microactuators, such as microvalves and micropumps, perform certain actions based on information they receive.

According to the MNX website, www.memsnet. org, the MEMS industry has developed microsensors for “almost every possible sensing modality, including temperature, pressure, inertial forces, chemical species, magnetic fields, radiation, etc.” The different types of microactuators are just as diverse, including “microvalves for control of gas and liquid flows, optical switches and mirrors to redirect or modulate light beams, independently controlled micromirror arrays for displays, microresonators for a number of different applications, micropumps to develop positive fluid pressures, microflaps to modulate airstreams on airfoils, as well as many others.”

Looking Ahead

According to Huff, while MEMS is currently an important segment of the vacuum market, due to the fact that the industry often uses dated and rebuilt vacuum equipment from the semiconductor field, its full potential as a growth driver for the vacuum industry has yet to be realized.

“I think that the growth of MEMS technology is definitely having a positive effect on the vacuum industry,” said Huff. “I won’t say it’s having a really huge effect yet because the MEMS guys are still using older IC equipment for the most part. So if you ask if this is good for the vacuum industry, I would say, ‘Yes.’ But is it going to make everyone in the vacuum industry a billionaire overnight? No.”

That said, with the recent surge in demand for MEMS technology from the Consumer Electronics market and the potential for its use in wearable devices and other advanced sensing technology, the MEMS industry could soon become much more integrated into the mainstream. And whether we realize it or not, MEMS is already a big part of our daily lives—and it stands to become even more so in the future.

“If I had to guess, I’d say the average person in the US probably owns around 10 MEMS devices right now,” said Huff. “They might not know they own them, but they do. You have a few in your cell phone, a few in your car… but if you had people using wearable devices and other applications controlling your house and office environment and things like that, it’s kind of easy to envision that this number could grow to a few hundred or even a thousand sensors per person. If you imagine all of the possible applications, then this could become a much different market at that point.”

With such vast potential for increased growth and revenue, it seems highly likely that MEMS fabrication will eventually become much more standardized. At that point, the rapid commercialization of MEMS technology that many have long predicted was just around the corner will finally come to fruition. And if this happens, the effect MEMS has on the vacuum industry could become exponentially greater.

“If we can get this industry to the point where it’s much more predictable, cost effective, and time effective for developing products,” said Huff, “then I think it would be a complete game changer, not only for MEMs, but for a lot of other industries, including vacuum.”