Microelectromechanical Systems (MEMS)
This electronic brochure highlights our capabilities and activities in the area of Microelectromechanical Systems. For additional information, e-mail Mike Ladika at bd@swri.org, Southwest Research Institute.
MEMS Technology
About the Cover: An SwRI-developed MEMS device undergoes testing in a probe station.
Institute engineers developed thermal actuators (top) operated by a differential expansion between two layers of dissimilar materials in each arm. To get the initial upward curvature, the device takes advantage of residual stresses in the film layers. The finite element model (middle and bottom) shows the device at rest (middle) and actuated (bottom) with the temperature profile that results from applying a current along the arms.
Test devices within MatLOC measure elastic modulus (top left), high-cycle fatigue (top right), and failure strength and strain data (bottom). Integrated LabVIEW Virtual Instruments provide automated test control, measurement, analysis, and reporting.
SwRI engineers characterize MEMS devices using this probe station and specialized data acquisition and analysis tools.
This scratch drive actuated device was the basis for a mechanical relay.
Micromirrors are a key component in optical MEMS applications. SwRI developed this latching mechanism to securely hold highly reflective gold-coated micromirrors in a vertical position.
Institute engineers developed this scalable, 2 x 2, free-space optical switch composed of electrostatically actuated cantilevers with vertically mounted micromirrors. The switch is designed for fiber-optic applications and can switch any input fiber to any output fiber.
The Institute's unique vacuum microprobe station provides a testing environment for developing MEMS for space applications. The facility can also be used for testing in a variety of partial pressure and controlled atmosphere environments.
SwRI engineers designed a device to control the flux of particles or photons into the entrance of a spectrometer. With a 10-micrometer overlap between the doors to ensure a tight seal, these devices can control a variable aperture width from fully closed to 90 micrometers wide when fully opened.
Microelectromechanical systems (MEMS) represent a growing technology with critical applications across diverse fields. Much of the industrial effort is directed toward replacing conventional technology with MEMS devices to reduce cost, increase functionality, improve reliability, and decrease size and mass.
MEMS research covers a wide range of technical areas. As a multidisciplinary, applied research and development organization, Southwest Research Institute (SwRI®) is uniquely suited for bringing together the technical expertise needed to design, develop, and package novel MEMS devices for a variety of applications.
The Institute has more than 55 years of experience in developing innovative ideas and aiding its clients in bringing new applications to the marketplace. As part of a long-held tradition, patent rights arising from sponsored research at the Institute are often assigned to the client. SwRI generally retains the rights to Institute-funded advancements.
The Institute provides integrated services in MEMS technology, including:
- Design and development
- Material properties evaluation
- Reliability assessment
- Performance evaluation
MEMS are used in diverse applications in areas such as space sciences, biotechnology, and manufacturing. Institute engineers and scientists offer expertise in:
- Sensors
- Switching
- Optical devices
- Space instrumentation
Product Development
Design and Development
SwRI has extensive experience in designing MEMS devices. After studying the problem and formulating the initial concept, engineers design mask layouts to form the device. During the design process, Institute staff members use fundamental and finite element techniques to evaluate different concepts and determine detailed dimensional requirements. The design layout information can be transmitted to a client-designated fabricator.
SwRI provides a variety of services to assist with MEMS development, including:
- Concept development
- System design
- Fundamental and finite element analysis
- Mask design layout services
- Fabricator coordination
- Device wet-etch release
- Wire bonding and packaging
In earlier studies, Institute engineers developed and characterized MEMS actuators that operate electrostatically or thermally. These actuators have a variety of operating characteristics, including:
- High force
- Rapid actuation speed
- Long travel distance
- Horizontal and vertical travel
- Resonance operation
Numerous MEMS devices can be built based on these actuators, which have been used in applications such as electrical relays, optical switching, and materials characterization.
Material Properties Evaluation
MEMS material properties are crucial for robust design and reliability assessment. Institute scientists and engineers have developed MatLOC - Materials Test Lab-On-a-Chip - for characterization of thin-film properties, including elastic modulus, fatigue strength, and fracture strength. MatLOC can be used to:
- Validate initial design assumptions
- Develop materials property-processing relationships
- Optimize fabrication processes
- Monitor quality assurance
- Characterize material properties statistically
Reliability Assessment
Variability and uncertainty in as-fabricated properties, dimensions, and boundary conditions on this small scale result in unique challenges in predicting MEMS performance. SwRI has developed probabilistic mechanics tools based on NESSUS® technology that enable these uncertainties to be accounted for in design and reliability assessment. These tools include:
- A suite of general-purpose, efficient probabilistic solvers
- Interfaces between NESSUS and commercial finite element solvers such as ANSYS®, ABAQUS, Dyna, and Nastran
- Interface technology to allow developers to interface easily with commercially available CAD systems for probabilistic MEMS design
Performance Evaluation
Characterizing MEMS devices is crucial to the design cycle. Properties are difficult to predict, fabrication parameters can vary, and numerous variables can affect performance. SwRI uses a variety of MEMS evaluation tools and facilities, including:
- Scanning electron and atomic force microscopes
- High-resolution optical microscopes
- Microprobe stations, for operation in air and vacuum environments
- Specialized signal-generation equipment
- Data- and image-acquisition equipment
- Class 10,000 clean room
- Wire bonding and wet-etch release stations
SwRI is also developing improved tools, including a three-dimensional MEMS profiling system for use with a standard probe station and a focused ion beam system that can deposit or etch small features or provide high-resolution imaging.
Applications
Sensors
SwRI engineers have developed low-cost, commercial MEMS devices to determine the capabilities, limitations, and appropriate approaches for using sensors in numerous applications, including:
- Corrosion detectors and monitors
- Automotive and aerospace instrumentation
- Biological and medical devices
- Chemical and environmental sensors
- Manufacturing and process control devices
- Virtual reality systems
Switching
SwRI engineers have developed numerous high-performance switches, including a mechanical relay timer switch that tolerates high electrical current. Because the silicon used to manufacture integrated circuits and MEMS devices cannot carry high current, this relay timer switch engages an external relay that can tolerate the current. Other forms of switching applications include:
- Radio frequency devices
- Microfluidics
- Optical devices
- Mechanical switches
Optical Devices
MEMS are well suited to optical applications because these applications require little force and displacement, very small size, low electrical power, and moderate to fast actuation speeds. MEMS-based optical devices can be used in:
- Bar code scanners
- Telecommunications switching
- Projection displays
- Adaptive optics
- Chemical spectroscopy
- Pressure and motion sensors
- Optical storage
SwRI has developed optical MEMS devices using in- and out-of-plane micromirrors for beam deflections. These devices include:
- Fiber optic switches
- Optical scanners
- Resonator frequency sensors
- Variable beamsplitters
- Microgratings
Space Instrumentation
Because of the cost of launching instrumentation into orbit, the rigors of the launch and space environments, and the need for high-reliability devices, MEMS technology is ideally suited to space applications. Alternatively, the loss of lubrication and dampening in the vacuum environment of space brings new challenges to MEMS device evelopment. SwRI scientists are at the forefront in developing MEMS components for a variety of space instruments, including:
- Energetic neutral atom imagers
- Mass spectrometers
- Plasma analyzers
- Variable aperture
This brochure was published in February 2003. For more information about microelectromechanical systems, please contact Mike Ladika, Senior Program Manager, Institute Business Development, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510.
