MEMS - Stands for Micro-Electro-Mechanical Systems, and are a trend in device manufacturing beyond eletronics. As the name says, we are talking of devices like computer chips that include also mechanical parts and optical parts.

Todays uses of MEMS technology seens to focus on creating optical devices with a tiny mounted mirror, that can project light in any direction, really fast, thus being able to function as a screen, by projecting this image in a surface, or even in one's retina.

Existing retinal projection displays using MEMS IC's exist today (6/2002) and are priced at a U$15000 tag. One of the main corporation working in MEMS production and fabrications is Microvision. You can read more about MEMS on their site at: .

MEMS is one of the coolest areas of modern engineering research. MEMS stands for microelectromechanical systems, but the term microsystems more accurately describes MEMS since they need not be mechanical. Generally, MEMS are micro-scale sensors, actuators, or mechanical structures. Some engineers believe that MEMS will be a revolution of similar magnitude to the integrated circuit and personal computer revolutions. MEMS researchers are from diverse fields such as electrical engineering, mechanical engineering, and biology.

A noteworthy example of a commercial MEMS sensor is the accelerometer found in car airbags. The main producer of accelerometers, Analog Devices, uses a fairly typical integrated circuit fabrication process to create CMOS and accelerometers on the same chip. The accelerometer is essentially a capacitor with one plate fixed and one plate able to move in response to accelerations, changing the capacitance.* The capacitance is continually analyzed by the CMOS circuitry, and if it changes too much, the circuitry directs the airbag to expand. The presence of moving parts is a common (but not required) feature of MEMS that is never present in integrated circuits. The most important method of creating moving parts in a microfabrication process is discussed in the node wet etching.

* Actually to increase surface area, an interdigitated finger structure is used for the varactor (variable capacitor) sensor.

There are other types of MEMS sensors that detect presence of chemicals, temperature, pressure, etc. These sensors usually have macroscopic counterparts. One interesting thing about MEMS sensors is that they can be integrated (not trivial but doable) with complex electrical circuits. Such integration has cost, reliability, and performance advantages. Furthermore, the tiny size of MEMS sensors suggests applications not possible with large-sized sensors. It is not difficult to imagine tiny MEMS chips inserted into blood vessels or into the digestive tract for medical purposes.

MEMS actuators are even more neat then sensors. Tiny rotary motors, electrostatically-driven moving beams, and even internal combustion engines have been formed using silicon microfabrication techniques. These are the sorts of things that engineers dream about; the future applications seem both limitless and fascinating. One "mundane" research idea with MEMS actuators is to use arrays of tiny mirrors to deflect light to different fibers for optical communication purposes. The movement of the mirrors could be dictated by circuitry integrated right along with them. A more visionary and fantastic use for MEMS actuators would be to create mobile microrobots. Sound crazy? I think microrobots will become commonplace in our lifetimes! Perhaps the biggest challenge will be finding an energy source for the miniature devices.

MEMS is also used to refer to tiny structural things that don't sense or actuate. Examples are the nozzles used in ink jet printers and channels used to direct the biological process polymerase chain reaction.

MEMS is definitely an up-and-coming and exciting field. It seems certain to find widespread commercial uses. Whether the MEMS revolution is really as dramatic as the integrated circuit revolution remains to be seen.

For more information about microfabrication, the node integrated circuit might be helpful.

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