A CMOS-compatible high aspect ratio silicon-on-glass in-plane micro-accelerometer

This paper presents a post-CMOS-compatible micro-machined silicon-on-glass (SOG) in-plane capacitive accelerometer. The accelerometer is a high aspect ratio structure with a 120 µm thick single-crystal silicon proof-mass and 3.4 µm sense gap, bonded to a glass substrate. It is fabricated using a simple 3-mask, 5-step process, and is fully CMOS compatible. A CMOS switched-capacitor readout circuit and an oversampled Σ–delta modulator are used to read out capacitance changes from the accelerometer. The CMOS chip is 2.6 × 2.4 mm2 in size, utilizes chopper stabilization and correlated double sampling techniques, has a 106 dB open-loop dynamic range, a low input offset of 370 µV, and can resolve better than 20 aF. The accelerometer system has a measured sensitivity of 40 mV g−1 and input referred noise density of 79 µg Hz−1/2. Using the SOG configuration, a post-CMOS monolithic integration technique is developed. The integration technique utilizes dielectric bridges, silicon islands and the SOG configuration to obtain a simple, robust and post-CMOS-compatible process. Utilizing this technique, an integrated SOG accelerometer has been fabricated using the University of Michigan 3 µm CMOS process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49037/2/jmm5_2_013.pd

Closed-loop electromechanical sigma-delta microgravity accelerometers.

Micromachined inertial sensors are one of the most important groups of silicon based sensors. High precision accelerometers with micro-gravity (mug) resolution have a number of applications including navigation and guidance, space microgravity measurements, and automotive industry. Recently, MEMS-based capacitive accelerometers have become very attractive due to their high sensitivity, low-temperature sensitivity, simple structure, low cost, drastically reduced size and weight, and low power dissipation. The objective of this thesis is to investigate the limitations of microaccelerometer systems and develop a micro-g resolution accelerometer system with its interface electronics for inertial navigation applications. The focus of this research is on the interface electronics and the system design. The interface electronics forms a 2nd order Sigma-Delta modulator together with the sensor and operates it in an oversampled electromechanical Sigma-Delta loop to read the sensor capacitance variation, force-rebalance the proof mass, and obtain a direct digital output. Closed-loop operation increases the dynamic range and reduces the sensitivity to variations in mechanical characteristics. The 1st generation interface circuit has a 95dB dynamic range and can resolve better than 75aF. The complete module has a measured acceleration sensitivity of 430 mV/g with 3.5mug/√Hz noise floor in open-loop. Closed loop operation of the system has been achieved for the first time and provides a resolution of 25mug/√Hz. Noise analysis of the 1st generation system shows that the interface electronics limits system performance. Therefore, a 2 nd generation interface circuit was been developed to achieve mug resolution. This chip operates from a 1MHz clock and provides an adjustable sensitivity between 0.2 and 1.2V/pF with a resolution better than 20aF and a dynamic range up to 140dB. It has been shown that this new circuit can resolve 1mug/√Hz in open-loop when it is combined with high-sensitivity out of plane (z-axis) accelerometers. By using this chip a complete 3-axis mug-resolution accelerometer system has been realized. In addition to the 2nd-order Sigma-Delta technique, a novel interface electronics design has been introduced for sub-mug resolution accelerometers. This new technique employs two accelerometers in a multi-step Sigma-Delta modulator architecture and provides high SNR while improving the dynamic range. It has been shown that this new architecture improves the system resolution by a factor of more than two compared to the 2nd-order Sigma-Delta modulator.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123423/2/3079479.pd

CMOS Cell Sensors for Point-of-Care Diagnostics

sensor

A hybrid Silicon-On-Glass (SOG) lateral micro-accelerometer with CMOS readout circuitry

A hybrid micro-accelerometer system consisting of a new bulk Silicon-On-Glass (SOG) lateral capacitive microaccelerometer and a CMOS interface circuit is presented. The accelerometer has a 120µm-thick proof mass, 2.2mm × 3.0mm in size with 3.2µm sensing gap defined by DRIE. The circuit has a 95dB dynamic range, a low offset of 370µV and can resolve better than 75aF. The hybrid system has a measured sensitivity of 40mV/g and resolution o

An electromagnetic micro power generator for low frequency environmental vibrations based on the frequency upconversion technique

This paper presents a microelectromechanical-system-based electromagnetic vibration-to-electrical power generator that can harvest energy from low-frequency external vibrations. The efficiency of vibration-based harvesters is proportional to excitation frequency, so the proposed generator is designed to convert low-frequency environmental vibrations to a higher frequency by employing the frequency upconversion (FupC) technique. It has been shown that the generator can effectively harvest energy from environmental vibrations of 70–150 Hz and generates 0.57-mV voltage with 0.25-nW power from a single cantilever by upconverting the input vibration frequency of 95 Hz–2 kHz. The fabricated generator size is 8.5×7×2.5 mm3, and a total of 20 serially connected cantilevers have been used to multiply the generated voltage and power. The generator demonstrated in this paper is designed for the proof of concept, and the power and voltage levels can further be increased by increasing the number of cantilevers or coil turns. The performance of the generator is also compared with that of a same-sized custom-made traditional magnet–coil-type generator and with that of a traditional generator from the literature to prove its effectiveness.[2009-0136

A Prominent Cell Manipulation Technique in BioMEMS: Dielectrophoresis

BioMEMS, the biological and biomedical applications of micro-electro-mechanical systems (MEMS), has attracted considerable attention in recent years and has found widespread applications in disease detection, advanced diagnosis, therapy, drug delivery, implantable devices, and tissue engineering. One of the most essential and leading goals of the BioMEMS and biosensor technologies is to develop point-of-care (POC) testing systems to perform rapid prognostic or diagnostic tests at a patient site with high accuracy. Manipulation of particles in the analyte of interest is a vital task for POC and biosensor platforms. Dielectrophoresis (DEP), the induced movement of particles in a non-uniform electrical field due to polarization effects, is an accurate, fast, low-cost, and marker-free manipulation technique. It has been indicated as a promising method to characterize, isolate, transport, and trap various particles. The aim of this review is to provide fundamental theory and principles of DEP technique, to explain its importance for the BioMEMS and biosensor fields with detailed references to readers, and to identify and exemplify the application areas in biosensors and POC devices. Finally, the challenges faced in DEP-based systems and the future prospects are discussed. View Full-Text Keywords: biochip; biomems; biosensors; cancer cells; diagnostics; dielectrophoresis; lab-on-a-chip; marker-free particle manipulation; multidrug resistance; point-of-car

Highly Integrated 3 V Supply Electronics for Electromagnetic Energy Harvesters With Minimum 0.4 V peak_{\mathbf{peak}} Input

This paper presents a self-powered interface enabling battery-like operation with a regulated 3 V output from ac signals as low as 0.4 V-peak, generated by electromagnetic energy harvesters under low frequency vibrations. As the first stage of the 180 nm standard CMOS circuit, harvested signal is rectified through an ac/dc doubler with active diodes powered internally by a passive ac/dc quadrupler. The voltage is boosted in the second stage through a low voltage charge pump stimulated by an on-chip ring oscillator. The output is finally regulated to 3 V at the last stage. The voltage doubling rectification stage deviates by less than 40 mV from ideal expectation for the validated 0.15-1 V input voltage range. The full system delivers 3 V output to 4.4 M Omega load for input voltage of 0.4 V-peak, which is the lowest operable input voltage in the literature. The demonstrated system generates 9 mu W of dc power with 3 V stable output for 32 mu W input, whereas the circuit is able to supply even more output power for higher input power levels. The maximum efficiency of the rectification stage is 86%, while the full system efficiency is 37% and 28% for unregulated and regulated operation, respectively, when interfaced to an in-house electromagnetic energy harvester under 8 Hz 0.1 g vibration

A parylene-based dual channel micro-electrophoresis system for rapid mutation detection via heteroduplex analysis

A new dual channel micro-electrophoresis system for rapid mutation detection based on heteroduplex analysis was designed and implemented. Mutation detection was successfully achieved in a total separation length of 250 μm in less than 3 min for a 590 bp DNA sample harboring a 3 bp mutation causing an amino acid change. Parylene-C was used as the structural material for fabricating the micro-channels as it provides conformal deposition, transparency, biocompatibility, and low background fluorescence without any surface treatment. A new dual channel architecture was derived from the traditional cross-channel layout by forming two identical channels with independent sample loading and waste reservoirs. The control of injected sample volume was accomplished by a new u-turn injection technique with pull-back method. The use of heteroduplex analysis as a mutation detection method on a cross-linked polyacrylamide medium provided accurate mutation detection in an extremely short length and time. The presence of two channels on the microchip offers the opportunity of comparing the sample to be tested with a desired control sample rapidly, which is very critical for the accuracy and reliability of the mutation analyses, especially for clinical and research purposes

An adaptable interface circuit for low power MEMS piezoelectric energy harvesters with multi-stage energy extraction

This paper presents a self-powered interface circuit to extract energy from ambient vibrations for powering up microelectronic devices. The system uses a MEMS piezoelectric energy harvester to scavenge power in 5 μW to 400 μW range. Synchronous electric charge extraction (SECE) technique is utilized to transfer harvested energy to output storage with the help of a novel multi-stage energy extraction (MSEE) circuit. The circuit is optimized in 180nm HV CMOS technology to operate with minimum power losses at the lowest allowable input power, and adjusts well to higher input power due to the MSEE circuit. The circuit operation was validated for a wide piezoelectric frequency range from 20 Hz to 4 kHz. Power efficiency between 62% and 81% has been achieved for the input power range of 5 μW to 173 μW at 198 Hz input vibration. MSEE provides up to 15% efficiency improvement compared to traditional SECE to keep power efficiency as high as possible for the full input power range.European Commission: FLAMENCO - A Fully-Implantable MEMS-Based Autonomous Cochlear Implant (682756