Microelectromechanical Systems Motion Research Articles

Millipixel image correlation for sub nm measurement of MEMS motion

A 1D digital image correlation algorithm capable of measuring the motion of microelectromechanical systems (MEMS) devices with sub nm resolution is presented. Successive micro photographic images are recorded, then subsets of the images are column averaged and the resulting 1D profiles are cross correlated. Factors that limit the correlation resolution are examined and methods for achieving millipixel level repeatability are discussed. Key to high resolution correlation of MEMS motion were low image noise and high sum of square of subset intensity gradients (SSSIG), a measure of image contrast. Using this correlation algorithm, the motion of MEMS thermal actuators was measured. Sub nm resolution was achieved using a wide range of image subsets, with measured standard deviations as low as 0.10 nm (0.6 millipixels).

Particle Tracking of Microelectromechanical System Performance and Reliability.

Microelectromechanical systems (MEMS) that require contact of moving parts to implement complex functions exhibit limits to their performance and reliability. Here, we advance our particle tracking method to measure MEMS motion in operando at nanometer, microradian, and millisecond scales. We test a torsional ratcheting actuator and observe dynamic behavior ranging from nearly perfect repeatability, to transient feedback and stiction, to terminal failure. This new measurement capability will help to understand and improve MEMS motion.

Advanced information processing of MEMS motion sensors for gesture interaction

Abstract. Sensor-based gesture interaction technology has been widely adopted in consumer electronics. Nevertheless, bias, drift, and noise existing in sensor signals are difficult to eliminate, and accurate movement trajectory information is still needed to achieve flexible interaction application. This paper presents micro-electro-mechanical system (MEMS) motion sensor information processing algorithms designed on a gesture interaction system which integrates multiple low-cost MEMS motion sensors with ZigBee wireless technology to support embodied communication while acting together with machines. Sensor signal processing systems mainly solve noise removal, signal smoothing, gravity influence separation, coordinate system conversion, and position information retrieval. The attitude information which is an important movement parameter and required by position estimation is calculated with a quaternion-based extended Kalman filter (EKF). The effectiveness of the movement information retrieval of this gesture interface is verified by experiments and test analysis, both in static and moving cases. In the end, related applications of the described sensor information processing are discussed.

Design of a 1 DOF MEMS motion stage for a parallel plane geometry rheometer

Rotational rheometers are used to measure paste properties, but the test would take too long to be useful for quality control (QC) on the job site. In this paper, a new type of rheometer is proposed based on a one degree of freedom (DOF) micro-electro-mechanical systems (MEMS)-based motion stage. Preliminary data will be presented to show the capability of the system to measure the viscoelastic properties of a paste. The parallel plate geometry rheometer consists of two plates, which move relative to each other to apply a strain to the material to be tested. From the stress measured and the strain applied, the rheological characteristics of the material can be calculated. The new device consists of an electrothermal actuator and a motion plate. For the rheological measurements, the device is designed to generate the shear stress up to 60 Pa and maintain its stiffness to less than 44 N/m. With these features, the device uses a square plate of 1.5 mm x 1.5 mm to provide enough area for a few micro-liter level volumes. The motion of the square plate is monitored by a capacitive sensor at the end of the oscillating plate which has a resolution of 1.06 μm. When a reference cementitious paste, Standard Reference Material (SRM)-2492, is placed between the oscillating plate of the presented motion stage and a fixed plate, the reduction in the displacement of the oscillating plate is monitored showing that the presented motion stage is reasonably designed to detect the response of the reference cementitious paste.

Research on a Novel Compensation Algorithm for MEMS Sub-Pixel Displacement Measurement

The sub-pixel allocation is a key technology for achieving high-precision measurement for micro electro mechanical system (MEMS). In this paper, a novel sub-pixel compensation algorithm based on an improved gradient algorithm utilized in a rough sub-pixel position is proposed to compensate the insufficient accuracy extracted by the surface fitting. And compared with traditional gradient used in the integer pixel, the proposed algorithm can reduce the error introduced by abandoning the higher order term without using iteration and second-order Taylor formula. The experimental results show that the displacement parameters calculated by the proposed algorithm is more accurate, and the method has a good noise resistance, it can meet high-precision positioning of MEMS motion image.

Large-Range MEMS Motion Detection With Subangström Noise Level Using an Integrated Piezoresistive Silicon Nanowire

Electrostatically actuated microelectromechanical systems (MEMS) devices integrating a surface micromachined silicon nanowire were batch processed to investigate motion detection with a nanowire piezoresistive gauge. In the proposed implementation, the nanogauge is indirectly coupled to the MEMS structure through an intermediate coupling spring. This design allows an arbitrary choice of MEMS motion detection range and a resolution improvement of in situ nanowire gauge factor measurements. Using this approach, it is demonstrated that an in-plane MEMS displacements up to 180 nm with a noise level down to 0.7 Å/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> can be achieved. MEMS resonance measurement in air and in vacuum by this method is also demonstrated. Results are compared with ex situ measurements of MEMS displacement by optical microscopy and by integrated capacitive detection.

Studies on the Polymer Adhesive Wafer Bonding Method Using Photo-Patternable Materials for MEMS Motion Sensors Applications

In this paper, various photo-patternable polymer adhesive materials were investigated for the selective wafer bonding of microelectromechanical system (MEMS) motion sensors. Commercially available photo-patternable materials which have different base polymer resins and photolithography mechanisms were selected. Curing behavior for each photo-patternable material was analyzed using the Fourier transform infrared spectroscopy to optimize the lower bonding temperature conditions with a sufficient degree of cure and wafer bonding process capability. Selective polymer adhesive wafer bonding method using photo-patternable materials was successfully demonstrated without any critical voids and defects except the phenol-based polymer resin. Also, mechanical properties, such as bonding strength and residual stress, and reliability were completely evaluated in order to select the best materials which meet the requirements for the piezoresistive MEMS motion sensors. The bonded wafers were strong enough to endure the dicing process. Bonding strength was measured quantitatively by a tensile test. The epoxy-based resin showed the best bonding strength with up to 42.9 MPa. Residual stress in the adhesive layer was evaluated using a wafer curvature measurement, because the residual stress may cause the changes of MEMS sensor performance. The silicone-based resin showed the lowest residual stress of 3 MPa because of lower Young's modulus. Five different reliability tests were performed to completely evaluate the reliability of the photo-patternable materials. The silicone-based resin showed the best reliability performance. As a result, photo-patternable polymer adhesive materials and wafer processing conditions were optimized for the MEMS motion sensors wafer bonding.

In-plane vibration characterization of microelectromechanical systems using acousto-optic modulated partially incoherent stroboscopic imaging

A technique using acousto-optic modulated partially incoherent stroboscopic imaging for measurement of in-plane motion of microelectromechanical systems (MEMS) is presented. Vibration measurement is allowed by using flashes of the partially incoherent light source to freeze the positions of the microstructure at 12 equally spaced phases of the vibration period. The first-order diffracted beam taken out by an acousto-optic modulator (AOM) from the light beam of a laser is made partially incoherent by a rotating diffuser and then serves as the stroboscopic light source. Both the MEMS excitation signal and the flash control signal are provided by a dual-channel function generator. The main advantage of this measurement method is the absence of a stroboscopic generator and a high speed digital camera. Microscale prototypes are fabricated and tested. Quantitative estimates of the harmonic responses of the prototypes are obtained from the recorded images. The results agree with those obtained with a commercial MEMS motion analyzer TM with relative errors less than 2%.

Manufacture of Micromirror Arrays Using a CMOS-MEMS Technique

In this study we used the commercial 0.35 μm CMOS (complementary metal oxide semiconductor) process and simple maskless post-processing to fabricate an array of micromirrors exhibiting high natural frequency. The micromirrors were manufactured from aluminum; the sacrificial layer was silicon dioxide. Because we fabricated the micromirror arrays using the standard CMOS process, they have the potential to be integrated with circuitry on a chip. For post-processing we used an etchant to remove the sacrificial layer and thereby suspend the micromirrors. The micromirror array contained a circular membrane and four fixed beams set symmetrically around and below the circular mirror; these four fan-shaped electrodes controlled the tilting of the micromirror. A MEMS (microelectromechanical system) motion analysis system and a confocal 3D-surface topography were used to characterize the properties and configuration of the micromirror array. Each micromirror could be rotated in four independent directions. Experimentally, we found that the micromirror had a tilting angle of about 2.55° when applying a driving voltage of 40 V. The natural frequency of the micromirrors was 59.1 kHz.

Initial studies on microelectromechanical system flux concentrators

To take advantage of the potential offered by the recent increase in the magnetoresistance of magnetic tunnel junctions, it is necessary to address the problem of 1∕f noise. ARL has been working on a device, the microelectromechanical system (MEMS) flux concentrator, that mitigates this problem by modulating the sensed magnetic field so that the sensor operates at a higher frequency region where the 1∕f noise is smaller. Initial results of testing the device are reported. Though the final step in the fabrication of the device appears to have adversely affected the MEMS motion, two important results were obtained. They are (1) applying the large amplitude voltage at kilohertz frequencies necessary to drive the MEMS structure does not increase the background noise and (2) even though the width of the drive voltage is several hertz, one can demodulate the signal using a lock-in amplifier in order to extract 1Hz modulation signals. This last result shows that the sensor can be used to detect slow moving or varying magnetic anomalies.

Low-power CMOS wireless MEMS motion sensor for physiological activity monitoring

In this paper, a short distance wireless sensor node "AccuMicroMotion" for physiological activity monitoring is proposed for detecting motions in six degrees of freedom. System architecture, relevant microstructures, and electronic circuits to implement the sensor node are presented. A three-axis microelectromechanical systems (MEMS) accelerometer and a z-axis gyroscope are designed and fabricated using a new deep-reactive ion-etch CMOS-MEMS process. The interface circuits, an analog-to-digital converter, and a wireless transmitter are designed using Taiwan Semiconductor Manufacturing Company 0.35-/spl mu/m CMOS process, wherein the interface circuits adopt chopper stabilization technique and can resolve a signal (dc to 1 kHz) as low as 200 nV from the microsensors; digitized outputs from the microsensors are transmitted by a 900-MHz amplitude-shift-keying radio-frequency transmitter that delivers a 2.2-mW power to a 50-/spl Omega/ antenna. The system draws an average current of 4.8 mA from a 3-V supply when six sensors are in operation simultaneously and provides an overall 60-dB dynamic range.