In the OSTI Collections: MEMS
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| Article Acknowledgement: Dr. William N. Watson, Physicist DOE Office of Scientific and Technical Information |
Reports available through SciTech Connect
Patents available through DOepatents
Report Cited in SciTech Connect
The information-processing components in today’s computers and communication devices are almost always microelectronic systems. The information put into and taken from them may result in or cause external actions by the people who work with them or machines directly connected to them.
Similarly small microelectromechanical systems, or MEMS,[Wikipedia] can also process information, but their information processing directly interacts with mechanical motion in the devices themselves. A MEMS is particularly useful when its job doesn’t require very large motions. Depending on its design, a MEMS can process data derived from small motions to act as a sensing device, or can produce particular small motions based on the information it has.
Building MEMS to perform tasks when possible offers considerable savings of space and material. The technology continues to be advanced by researchers who develop new ways to use MEMS and who increase our understanding of the processes that affect MEMS and make them effective. A sample of recent reports available through OSTI indicates the variety of problems being addressed to make these advances.
One example of MEMS being used as sensors was devised by researchers at Lawrence Livermore National Laboratory and the University of California, Davis to measure stresses between solid surfaces that are ordinarily in direct contact. This type of device, being only 0.150 millimeters thick, can be placed unobtrusively between the surfaces so that the device’s presence doesn’t appreciably distort the stress that it’s supposed to measure. Since its sensing element is made of silicon, the device is flexible and durable enough to function through many load cycles without permanent distortion. The device contains a diaphragm that bends when undergoing a stress perpendicular to its surface, with four resistors at its edges arranged[Wikipedia] so that changes in the currents through them correlate with the stress to be measured. The researchers described their “Thin Silicon MEMS Contact-Stress Sensor” in a poster[SciTech Connect], an article[SciTech Connect], and an abstract[SciTech Connect] prepared for a 2010 workshop on solid-state sensors, actuators, and microsystems.
Figure 1. Upper left: Sensing element of a MEMS contact-stress sensor placed on a US penny for scale. Lower left: Closeup of sensing element showing the flexible diaphragm, the resistors at its edge, and the resistors’ electrical connections. The diaphragm in this element is 1000 micrometers (1 millimeter) in diameter; devices of the same type with different-sized diaphragms accommodate different ranges of stress. Upper right: A complete device, with the sensing element and electrical connections inside a flexible polyimide package, placed on a dime for scale. Lower right: Cross section of a complete device (not to scale), showing the sensing element in red, a shim in blue, electrical connection in orange, and polyimide coverlays in green. Different devices can be arbitrarily shaped for a variety of applications while having a uniform standard thickness of less than 150 micrometers. (From “Thin Silicon MEMS Contact-Stress Sensor”[SciTech Connect].)
These workshop reports described finished products very briefly. In contrast, two other Lawrence Livermore reports about a different project say more about the kind of thing normally faced in an ongoing project: the numerous ancillary problems one generally has to solve to make a relatively simple idea work. The reports, both entitled “Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection”[SciTech Connect;SciTech Connect] , describe a project to improve on current methods of detecting leaks in containers of chemically inert gases—an important ability in the surveillance of nuclear-weapon stockpiles—by using MEMS-based oscillators whose natural vibration frequencies change as the composition of gas around them changes and impedes their vibrations differently.
Experiments with a set of such oscillators showed that the frequencies of their least rapid vibrations, in their first vibrational mode, were affected by changes in the ambient gas composition and temperature, while changes in the higher frequencies of the MEMS’ fourth vibrational mode were almost entirely due to changes in gas temperature rather than gas composition. Also, vibrations of the first mode were found to fade out in fewer vibration cycles at higher temperatures, which according to a mathematical model of the system should happen due to the oscillator material softening as its temperature increased. According to the same mathematical model, changes with temperature in the intensities of different-frequency vibrations should be due almost entirely to changes in the density and viscosity of the surrounding gas, rather than changes in the oscillator itself. The researchers thus found that comparing the intensities of the MEMS’ vibrations in their first and fourth vibrational modes should allow the devices to detect gas leaks, by distinguishing changes in gas composition, which would naturally result whenever different gases escape from a leaking container at different rates, from changes in gas temperature, which would not change the gas composition.
Researchers at Sandia National Laboratories and the University of Maryland, investigating how lithium-ion batteries[OSTI] degrade during operation, devised and demonstrated an optical sensor for observing changes in the mechanical and chemical structure of the batteries’ cathodes. Since these changes reduce the capacity of lithium-ion batteries and limit how many charge/discharge cycles they can last, detailed observations of how they happen may help researchers figure out what might be done about them. Existing methods of observing the changes typically involve inspecting the battery after operation, not during, via bulky equipment in complex electrochemical apparati, and typically indicate either mechanical or chemical changes, but not both, even though both types of change are inherently coupled.
As they describe in their report “In-situ, Real-Time Monitoring of Mechanical and Chemical Structure Changes in a V2O5 Battery Electrode Using a MEMS Optical Sensor”[SciTech Connect], the Sandia-Maryland group was able to monitor both the chemical and the mechanical changes by constructing batteries whose cathodes have flexible membranes fixed upon them. When the batteries are charging and their cathodes expand as they take up lithium ions, the membranes bend; when the batteries discharge and their cathodes contract as lithium ions are extracted from them, the membranes flatten. During these processes, laser light waves shining through glass covers onto the membranes are monitored. The portions of the waves that reflect from the glass and the membranes interfere with each other, reinforcing at some points in space and cancelling at others[Wikipedia], with the reinforcement/cancellation pattern changing as the shape of the membranes changes during the batteries’ operation. Other laser beams shining through the glass and membranes have their frequency changed as they interact with the electrode material[Wikipedia], with these changes depending on the electrodes’ composition.
Figure 2. (a) Three-dimensional diagram and cross section of a MEMS optical sensor for monitoring changes in a lithium-ion battery’s cathode. (b) Schematic representation of the sensor’s principle of operation. As lithium ions are inserted into the cathode and extracted from it, changes in the cathode bend the flexible membrane that covers the cathode at the bottom of the Fabry-Perot[Wikipedia] cavity. The interference pattern between waves of the Fabry-Perot laser that are reflected from the flexible membrane and from the glass plate over the cavity is changed when the membrane’s shape is changed, thus registering mechanical change in the cathode. Meanwhile, the Raman laser beam’s frequency is altered by interaction with the cathode itself in a way that depends on the cathode’s chemical composition; changes in the frequency alteration register chemical changes in the cathode. (From “In-situ, Real-Time Monitoring of Mechanical and Chemical Structure Changes in a V2O5 Battery Electrode Using a MEMS Optical Sensor”[SciTech Connect], p. 2.)
Much work on microelectromechanical systems has resulted in patents. Several MEMS patents have been assigned to Sandia Corporation, which manages and operates Sandia National Laboratories. Two of these patents describe sensors in which light waves interact with some of the sensor components. As these components move, the paths of the light waves that interact with them also change, thus changing the waves’ interference patterns, which the sensors detect. Since the components in each type of sensor are set up to move in response to different changes in their environments, they sense different things.
The sensor described in US Patent 8,205,497[DOepatents], an acceleration detector, has an oscillating component that rotates back and forth, whose position or orientation will change whenever the size or direction of the sensor’s velocity is changed (i.e., when the sensor is accelerated). These changes in the oscillating component can both be detected by their effect on light waves, making the sensor an improvement on accelerometers that only detect changes in their velocity’s size (speed) or direction, but not both. In the other sensor of US Patent 8,674,689 (“Optically transduced MEMS magnetometer”[DOepatents]), one component conducts an alternating current. If the component is in a magnetic field not aligned with the current, the field will deflect the current from side to side as the current alternates back and forth, thus inducing an alternating deflection in the component that conducts the current. Other magnetometers do this much, but they detect the deflection by electrical effects, which suffer from crosstalk with the deflecting current and from other limitations on their sensitivity, instead of detecting the deformation by its effect on light waves.
In both these devices, the moving components have diffraction gratings attached. Light waves scattered from these gratings interfere with each other, producing one pattern when the components are in their “neutral” positions and different patterns when the components move. Detecting changes in the light waves’ diffraction pattern thus shows whether the devices are being subjected to accelerations or magnetic fields, depending on what their moving components are designed to respond to. The accelerometer patent notes the interest in developing such microdevices for navigational, automotive, and computer-control purposes; the magnetometer patent notes the limited sensitivity and dynamic range of other magnetometers that its own operating principle is intended to overcome.
Figure 3. Diagram of a magnetic-field sensor of the general type described in the patent “Optically transduced MEMS magnetometer” (US Patent 8,674,689 [DOepatents]). As the component carrying an alternating current is caused to vibrate by an ambient magnetic field, the grating on its surface also vibrates, thus changing the diffraction pattern of the light waves that scatter from it. The change in the waves’ diffraction pattern indicates the strength of the magnetic field. Similar changes in light waves’ diffraction from a grating attached to an accelerated component are used in the device described in US Patent 8,205,497 (“Microelectromechanical intertial sensor”[DOepatents]) to detect the device’s acceleration. (Figure from “Optically transduced MEMS magnetometer”[DOepatents].)
Other patents assigned to Sandia Corporation are for MEMS that produce small motions in response to some input.
Gas molecules move constantly and, except for their collisions with each other or with the walls that bound the volumes they occupy, they move freely, with an average distance between collisions that depends on the gas density. If a gas occupies a pore whose width is about the same as this average intercollision distance or less and whose temperature increases along the pore’s length, the gas molecules will tend to move in the direction of the temperature increase. This tendency is the basis of a type of pump that uses temperature gradients along narrow pores instead of the action of moving parts to transfer gas from one place to another. The patent “Microelectromechanical pump utilizing porous silicon”[DOepatents] (US Patent 7,980,828) describes a porous device that can serve as part of a MEMS to move gas in this way. The device can be constructed with pores of any width from 10 nanometers to 10 micrometers or more, while the pump based on them can be integrated with other MEMS for handling gases. The integration can involve multiple pumps of the same type, tailored to operate at different pressure ranges in sequence, each using a temperature increase to move gases forward a step at a time against the opposition of successive pressure increases.
An adjustable electric circuit element is offered by the invention described in “Microelectromechanical tunable inductor”[DOepatents] (US Patent 7,710,232). Electric charges in motion are accompanied by a magnetic field whose strength is greater wherever more charge moves through a given space in a given time. These magnetic fields always exert forces that oppose any acceleration of the charges, the forces being greater when the magnetic fields are stronger. When charges flow through an electrically conducting coil, the space occupied by the multiple turns of conductor looped into the coil has more charge flowing through it per second than the space crossed by the single strand of conductor leading into or out of the coil, so the magnetic field around the coil is also greater—more so, the more turns there are in the coil—and thus oppose any acceleration of the charge more strongly.
An inductor, like the one mentioned in the patent title, is basically a conducting coil. If an inductor’s winding can be adjusted or tuned, how much it opposes acceleration of the electric charges that flow through it can also be tuned, making the charges’ motion more controllable. The MEMS described in the “Microelectromechanical tunable inductor” patent contains just such a tunable inductor. This inductor is a pair of minute conducting coils that can be made to roll or unroll, thereby strengthening or weakening the magnetic field of electric charges that flow through them and allowing control of the flow.
Other labs have also patented MEMS actuators. UT-Battelle, LLC, the contractor that manages and operates Oak Ridge National Laboratory, was assigned a patent entitled “MEMS based pyroelectric thermal energy harvester”[DOepatents] (US Patent 8,519,595) that addresses the problem of using the waste heat that industrial processes constantly produce. According to the patent, industry’s worldwide output of low-grade waste heat averages about 3 megawatts. There are fundamental thermodynamic limits on how much of this could be turned into useful energy[Wikipedia], but present-day conversion technologies have their own limits that keep us from achieving what is fundamentally possible. The energy harvester described in this patent is designed to produce electric currents driven by waste heat.
The energy harvester includes an electrical circuit containing a capacitor—a sandwich of an electrical insulator between two conducting plates—in which the electrical insulator is also electrically polarizable. When the insulator is cooled, the positive and negative charges that it’s made of separate somewhat, so that the upper and lower surfaces next to the conducting plates have opposite charges. Negatively charged electrons from the electrical circuit are attracted to the positive side of the insulator and flow as a current onto the corresponding conducting plate, while electrons are repelled from the conducting plate next to the insulator’s negative side and are driven into the rest of circuit, constituting a current there. The opposite happens when the insulator is warmed: its positive and negative charges become less separated, leaving less charge on the surfaces next to the conducting plates, so that the opposing charges on those plates are attracted less and the electron current flows the opposite way through the circuit. The faster the insulator’s temperature rises or falls, the more energetic the electric current and the more efficiently thermal energy from the heat source is harvested as electrical energy.
As shown in Figure 4, the insulator (component 60 in the figure) is made to undergo rapid heating and cooling because the conducting plates around it act like a bimetallic thermostat, bending one way when heated and the opposite way when cooled. This bending rapidly alternates the capacitor (plus the thermal conductors attached to it) between a waste-heat source and a heat sink. When the upper thermal conductor contacts the heat source, the insulator warms and depolarizes, and electrons accumulated on the capacitor flow back into the circuit. The capacitor plates also warm up and the capacitor quickly bends the other way. This puts the lower thermal conductor in contact with the heat sink, cooling the insulator and allowing its positive and negative charges to separate, thus driving electrons in the circuit the other way to accumulate on the capacitor. The cooled capacitor then bends back toward the heat source and the cycle repeats. The device thus takes energy from the waste-heat source to drive a rapidly alternating current, recycling what would otherwise be wasted energy into a useable form.
Figure 4. Top: Thermal conductors (70) are attached to a sandwich of electrically conducting plates (40 and 50) around a polarizable electrical insulator (60). On the left (a), this assemblage is in thermal contact with a heat sink (20) and rapidly cools, so that the insulator loses its polarization. After a short cooling period, the conducting plates bend into a different shape and raise the assemblage into contact with the higher-temperature source (10) of waste heat from some process, as shown on the right (b). In this position, the assemblage absorbs energy from the heat source, repolarizing the insulator and causing the conducting plates to bend back the other way, putting the assemblage back in contact with the heat sink (a). Bottom: As the insulator polarizes, its positive and negative charges separate slightly. If the insulator is connected to an external electric circuit, the insulator’s positive surface attracts negatively charged electrons through the circuit to that surface’s neighboring conducting plate, while the insulator’s negative surface repels electrons from its neighboring conductor, which go into the external circuit. When the insulator loses polarization, its positive and negative charges get less separated, which induces the electrons to travel through the external circuit in the opposite direction. Thus the back and forth motion of the insulator-conductor assemblage results in an alternating current through the external circuit, with the current driven by energy extracted from the source of waste heat. (After “MEMS based pyroelectric thermal energy harvester”[DOepatents], US Patent 8,519,595.)
All these patents describe MEMS whose functions can be used in many different ways. Another report, about work done at Lawrence Livermore National Lab, Boston Micromachines Corporation, and the University of Wisconsin—Madison, describes in detail how a particular set of MEMS was made for use in a single device—a camera designed for the Gemini Observatory’s telescope in Chile to take pictures of planets outside our solar system that orbit other stars many light-years away from the Sun. Like the aforementioned reports on developing sensors for gas-leak detection, “The use of a high-order MEMS deformable mirror in the Gemini Planet Imager”[SciTech Connect] gives considerable detail about the technical problems addressed and solved. In this case, the main problem was to continually adjust the shape of the camera’s flexible light-gathering mirror, so that its shape would always compensate for the lightwave-distorting effects of turbulence in the atmosphere, and produce clear images of any exoplanets in its field of view despite the turbulence. The basic solution was to make a mirror with 4,096 MEMS on it that would each adjust the angle of its small portion of the mirror to give the whole mirror a continually optimized shape. One of the numerous subproblems addressed was the fact that, with present manufacturing techniques, even in the best mirrors a few of the 4,096 MEMS would be defective. The solution to this subproblem involved detecting the defective MEMS and working around their limitations, which made the control system somewhat more complex than one sufficing for uniformly flawless MEMS.
Still other investigations have dealt with characterizing the behavior of microelectromechanical systems. Several groups have investigated how well various MEMS devices stand up to use.
Many applications of microfluidic devices[OSTI] involve distributing gases at finely specified pressures and times. Experiments made to check the suitability of some early microfluidic-valve designs and guide their improvement are described in the Sandia National Laboratories report “Preliminary characterization of active MEMS valves”[SciTech Connect]. The particular valves tested, according to the report, “are designed such that the valve boss is held at a ground, with a voltage applied to lower contacts. Resulting electrostatic forces pull the boss down against a series of stops, intended to create a seal as well as prevent accidental shorting of the device.” The valves being tested were electrostatically activated; their deformation under variable pressures and voltages was examined, along with other issues that inhibit performance.
Two models of valve were tested. The first model was found to have serious faults: the valves appeared to be structurally inferior to other valves, seemed likely to fail under given pressures before other designs would since they deformed much more, and displayed significant shorting. The report’s author stated that this model’s fabrication method needed to be modified after identifying the location and cause of the shorts, and that the other valve model showed more promise, though the shorts detected in those valves might indicate a larger problem that could arise in future fabrications and so should be explored as well. The author suggested that automated digital control and measurement of voltage, pressure, and flow rates should be done to narrow down the ranges over which the valves operate.
Finding the failure points of MEMS under tension was the subject of a different project by researchers at Sandia and Carnegie Mellon University, reported in “Predicting fracture in micron-scale polycrystalline silicon MEMS structures”[SciTech Connect]. Knowledge of how structures can fail can be used to design them in ways that avoid failure. However, measuring “the” strength of microdevices made of polycrystalline silicon presented at least two problems: polycrystalline silicon is brittle, with inhomogeneous distributions of critical flaws or defects, so even identical shapes made from it will break under very different tensions; and it was unclear what even a known tensile-strength distribution for simple shapes implied about the strength of complex MEMS structures.
This report was more definitive than the report on the preliminary MEMS valve characterization. Using two new high-throughput test techniques on about 1300 micrometer-sized polycrystalline silicon bars to determine the distribution of their tensile strengths, the report’s authors found a strength threshold, which implied that the method used to make the bars produced flaws that were all less than some maximum size. They also investigated several variations in the bars but found, from both experimental observations and mathematical analyses, that only sidewall edge flaws seemed to be a dominant contributor to the bars’ tensile-strength variations. These facts gave the researchers enough information to determine the strength of complex MEMS structures with micrometer-sized stress concentrations; their estimated lower bound for the strength of a double edge-notch specimen “compared favorably with measured values”.
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Figure 5. Scanning electron microscope pictures of on-chip strength tester for micrometer-sized polycrystalline silicon bars (upper left), a portion of a chain of bars to be tested (lower left), fracture surfaces of polycrystalline silicon bars, with arrows indicating apparent evidence of fracture origins (right). (From “Predicting fracture in micron-scale polycrystalline silicon MEMS structures”[SciTech Connect], pp. 27, 41.)
Another Sandia project is the development of a MEMS device for sensing a shock—an acceleration greater than a particular value—and latching an electrical contact into a closed position when one happens.[SciTech Connect] The devices are intended to function for many years in environments that might gradually degrade them in various ways, such as loss of electrical contacts within a device, increase of switch contact resistance, and exposure of components to gases or moisture. To see in a short time how proposed designs are likely to function over the long term, 37 devices were subjected to an accelerated aging process in which short-term effects (between 100 hours and 1 year) at high temperatures (100 °C and 150 °C) stood in for long-term effects (up to 20 years) at normal-use temperatures. The mathematical model underlying the experiment is reported in “The Sandia MEMS Passive Shock Sensor: Dormancy and Aging”[SciTech Connect], as are the results of the tests (100% of the devices continued to function normally).
MEMS have been advocated for measuring the conditions inside nuclear reactors, but whereas other types of sensors had been tested to see how the reactors’ radiation affects them, little research had been done to determine how radiation would affect MEMS sensors. The first reported test results of pressure and acceleration sensors in nuclear reactors are found in “Performance of commercial off-the-shelf microelectromechanical systems sensors in a pulsed reactor environment”[SciTech Connect] from Los Alamos National Laboratory. Samples of commercially available MEMS were tested—two models of accelerometer and three models of pressure sensor. When these devices are put under strain, thus changing the spacing of their atoms, the devices’ resistance to electron flow among their atoms also changes; the resistance change is measured to determine the accelerations or pressure changes that produce the strains. As long as radiation in the devices’ environment doesn’t affect how their resistance changes under pressure or acceleration, their accuracy in a high-radiation environment can be relied on. Only one pressure sensor showed noticeable degradation for gamma-ray doses below 20 kilograys and particle fluences under 20 neutrons per square nanometer; for irradiations up to 6 times as great, a different pressure-sensor model from the same manufacturer did better, with some samples failing while others continued to function. Only one accelerometer lost function under high neutron fluence (at 8 neutrons per square nanometer), with the rest showing no signs of catastrophic failure.
These investigations of MEMS’ behavior showed how they respond to different external influences. For successful MEMS design, it’s also important to understand the interactions of components within the MEMS itself. One such set of interactions was studied in a project described in the University of Florida report “Collective behaviors of the Casimir force in microelectromechanical systems”[SciTech Connect]. The “Casimir force”[Wikipedia] is named for the physicist Hendrik Casimir, who calculated how parallel plates with infinite conductivity and zero electric charge would alter the lowest-energy state of the electromagnetic field in the space they occupied. According to Casimir’s calculations, the energy of the electromagnetic field’s lowest-energy state would decrease as the conducting plates moved closer together. This being the case, the electromagnetic field would tend to push the plates together, so that if the plates were free to move their kinetic energy would increase at the expense of the field’s energy. Objects of other shapes and finite conductivity, though altering the state and energy of an electromagnetic field in different ways, would also experience similar Casimir forces that would tend to transfer energy to them from the field. Casimir forces between uncharged conductors are very weak except when the conductors are within a micrometer of each other, but then the Casimir forces are not only strong, but dominant. Conductors as close together as that are found in every microelectromechanical system.
Calculations of Casimir forces’ strength on different sets of objects began in the late 1940s with Casimir’s own work, but experiments to actually measure them precisely were first done in 1997. The University of Florida project, conducted in collaboration with researchers at the Hong Kong University of Science and Technology, Harvard, MIT, and Oak Ridge National Laboratory, was to test calculations of Casimir forces’ strength between various objects by using MEMS to measure those forces—not only between different objects such as nanoscale corrugations, planes, and spheres, but between microfabricated beams formed on the same chip together with the devices for controlling the beams’ separation and sensing the Casimir force between them. This latter arrangement overcomes difficulties encountered in experiments with separate objects, as the report explains:
For instance, maintaining the parallelism of two flat surfaces at small distances has proven to be difficult. As a result, in most experiments one of the two objects is chosen to be spherical. The alignment becomes even more challenging for nanostructured surfaces. In fact, when corrugations are present on both surfaces, it is necessary to use an in-situ imprint technique such that the patterns are automatically aligned after fabrication. Another major difficulty in measuring the Casimir force at room temperature is the long-term drift in the distance between the surfaces: since the distance from the two interacting elements to their common point of support typically measures at least a few centimeters, temperature fluctuations lead to uncontrollable distance variations, limiting the duration of measurement and hence the force resolution. (P. 7.)
By integrating the interacting elements, actuator, and sensor into a single MEMS,
No external alignment of the interacting bodies is necessary because they are defined in a single lithographic step. Another advantage is that the distance of the interacting elements to their common support is reduced to ~ 70 µm, about a factor of 1000 smaller than conventional experiments. The improved mechanical stability minimizes long-term drifts in the gap between the interacting objects (<10-5 nm s-1). Furthermore, this scheme also opens opportunities for future experiments to investigate the Casimir force using lithographically defined structures of nonconventional shapes. (Pp. 7-8.)
The report’s author notes that the group’s results represent the first step toward on-chip exploitation of the Casimir force, and that their single-MEMS component integration provides new opportunities to tailor those forces by tailoring the components’ shapes, which can be complex but automatically aligned. However, even the relatively simple corrugated shapes already experimented with make the Casimir forces between them difficult to calculate; the author concludes his summary of project accomplishments by noting “much progress will be necessary, particularly in sample fabrication and characterization, to achieve the < 5% agreement between theory and measurement that has been claimed in conventional Casimir force experiments between spheres and plates.”
Figure 6. Setup of experiment and device described in the report “Collective behaviors of the Casimir force in microelectromechanical systems”[SciTech Connect] for measuring Casimir forces between comb-shaped micromechanical structures. (a) A simplified schematic, not to scale, of a beam, movable electrode, and comb actuator supported by four springs, with electrical connections. The current amplifier provides a virtual ground to the right end of the beam. The suspended and anchored parts of the comb actuator are shown in dark and light colors respectively. The separation between the beam and the movable electrode was controllably reduced so that the Casimir force could be detected. (b)-(e) Scanning electron micrographs of the entire micromechanical structure (b) and closeups of: the doubly clamped beam (c), zoomed into the white dashed box in (b); the comb actuator (d) and the serpentine spring (e). (After p. 8, ibid.)
Wikipedia
- Microelectromechanical systems
- Wheatstone bridge
- Fabry-Pérot interferometer
- Raman spectroscopy
- Carnot’s theorem (thermodynamics)
- Casimir effect
- Lawrence Livermore National Laboratory
- University of California, Davis
- Sandia National Laboratories
- University of Maryland
- Sandia Corporation
- UT-Batelle, LLC
- Oak Ridge National Laboratory
- Boston Micromachines Corporation
- University of Wisconsin—Madison
- Gemini Observatory
- Gemini Planet Imager
- Carnegie Mellon University
- Los Alamos National Laboratory
- University of Florida
- Hong Kong University of Science and Technology [traditional and simplified Chinese versions]
- Harvard University
- Massachusetts Institute of Technology
Reports available through SciTech Connect
- “Thin Silicon MEMS Contact-Stress Sensor” [Metadata, first, second, and third versions]
- “Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection” [Metadata, earlier and later reports]
- “In-situ, Real-Time Monitoring of Mechanical and Chemical Structure Changes in a V2O5 Battery Electrode Using a MEMS Optical Sensor” [Metadata]
- “The use of a high-order MEMS deformable mirror in the Gemini Planet Imager” [Metadata]
- “Preliminary characterization of active MEMS valves” [Metadata]
- “Predicting fracture in micron-scale polycrystalline silicon MEMS structures” [Metadata]
- “The Sandia MEMS Passive Shock Sensor: FY08 Design Summary” [Metadata]
- “The Sandia MEMS Passive Shock Sensor : Dormancy and Aging” [Metadata]
- “Performance of commercial off-the-shelf microelectromechanical systems sensors in a pulsed reactor environment” [Metadata]
- “Collective behaviors of the Casimir force in microelectromechanical systems” [Metadata]
Patents available through DOepatents
- “Microelectromechanical inertial sensor” (US Patent 8,205,497) [Metadata]
- “Optically transduced MEMS magnetometer” (US Patent 8,674,689) [Metadata]
- “Microelectromechanical pump utilizing porous silicon” (US Patent 7,980,828) [Metadata]
- “Microelectromechanical tunable inductor” (US Patent 7,710,232) [Metadata]
- “MEMS based pyroelectric thermal energy harvester” (US Patent 8,519,595) [Metadata]
Report Cited in SciTech Connect
- “Casimir Forces On A Silicon Micromechanical Chip” [Metadata]
- “Development of MEMS based pyroelectric thermal energy harvesters” [Metadata]
- Solid-State Sensors, Actuators and Microsystems Workshop, Hilton Head, South Carolina, June 6-10, 2010
- In the OSTI Collections: Lithium-Ion Batteries
- In the OSTI Collections: Microfluidics
