Q. What are MEMS?
A. MEMS stands for Microelectromechanical systems. They are miniature devices that enable the operation of complex systems. Smaller than a grain of sand, MEMS devices combine tiny mechanical, optical and fluidic elements with electronics and are integrated on a silicon chip. Typically MEMS devices act as sensors, actuators, pumps and valves. Because of their small size, MEMS are frequently more precise in their operation than their larger machined counterparts.
Q. Where are MEMS used?
A. MEMS are used in automotive, military, medical, telecommunications and aerospace industries. MEMS devices serve as impact sensors in the accelerometers of automobile airbags. They are also the micronozzles in commercial inkjet printers. Biomedical applications include acting as tiny blood pressure sensors. MEMS can be found in video projection chips and throughout Boeing 747 airliners – from engine blades to the wheels.
Q. How are MEMS manufactured?
A. MEMS microstructures are manufactured in batch processes similar to computer microchips. The lithographic techniques that mass-produce millions of complex microchips can also be used simultaneously to develop and produce mechanical sensors and actuators integrated with electronic circuitry. The processes are based on depositing thin films of metal or crystalline material on a substrate, which are then etched away selectively, leaving multi-layered 3-D features behind.
Q. Where will MEMS be used in the future?
A. A lot of research into new uses for MEMS is based on military and aerospace applications. One application still being developed is “smart dust” where MEMS sensors will be deployed in the air to measure pollution. Other innovative applications include “smart roads” where MEMS devices would be laid out as a blanket on the roadbed to measure physical conditions and traffic and report the information to geo-positioning systems mounted in cars. MEMS devices are also being used in optical networks and wireless communications.
Q. When did MEMS become commercially viable?
A. MEMS have been studied in the lab since the early '60's, but the first commercial use was in the early 1990's in the automotive industry, with the advent of MEMS-based pressure sensors and accelerometers
Q. What are the challenges in designing MEMS devices?
A. Several design-related factors have prevented MEMS from being developed and deployed on a larger scale. The first is finding skilled engineers with an adequate knowledge of micromechanical systems, materials and target manufacturing processes. Second is the challenge of transferring data between separate electronic and mechanical design teams who handle “system” and “component-level” development. Neither team shares tools, methodologies or intellectual property with the other, choosing instead to “throw it over the wall” to the other team. Third, as a result of this isolated approach, product teams have been unable to leverage time-saving design reuse techniques and the availability of component intellectual property.
CAD software tools designed for MEMS may provide a system-level approach enabling designers to develop new MEMS designs, integrate existing designs (intellectual property, or IP), and couple them with the system electronics that will drive them. Some CAD tools are open platform products that support the leading electronic design automation environments used for integrated circuit development and allow data sharing between system designers, IC designers, process engineers and MEMS experts, enabling earlier and consistent design checks between multidisciplinary teams.
Volume manufacture of MEMS has also proved to be an obstacle. While development of prototypes can offer a validation of a solution, taking that prototype into high-volume manufacture typically requires a significant amount of work in developing a manufacturing process to consistently produce the results demonstrated in the prototype. Additionally, the process must ensure adequate yields of MEMS devices per wafer to make the solution cost-effective in volume. Teams of process specialists are often required to achieve successful MEMS manufacturing methodologies.
