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With increasing air pollution levels across the globe, there has been a significant increase in the global health crisis. But the problem remains unchecked in various parts of the world, due to the lack of low-cost and high accuracy air quality sensors. This paper proposes a new technique based on piezoelectric micro-electro-mechanical systems (MEMS) to measure the amount of particulate matter (PM) suspended in the air. Commercially available PM sensors suffer from many disadvantages - namely size, cost, and accuracy. Previous attempts at using MEMS to measure PM have failed to make a significant impact due to the lack of a mechanism to sort the suspended particles based on their sizes and clear the sensing area from the particles after each measurement. The sensor proposed here, consisting of i) a piezoelectric resonating membrane, ii) a virtual impactor, and iii) a thermophoretic plate attempts to address the issues faced by other sensors, while achieving a very compact size and a significantly lower cost. On exposing the sensor to suspended particles in a container, a significant shift in the resonant frequency is observed, once the particles settle on the resonating membrane. The gradual shift in the resonant frequency supports the application of the proposed sensing solution to measure the mass of the PM in the air.

This paper reports on the design and fabrication of metal-oxide gas sensors, utilizing aerosol jet printing, combined with microhotplates fabricated through a process based on the industrial PolyMUMPs technology. Fabrication is complemented with in-house post-processing steps that do not require additional alignment or dry etching equipment, which greatly reduces the fabrication complexity. Aerosol jet printing is used to deposit thin homogeneous metal-oxide films, with micron thickness. A heating temperature over 300 °C is achieved by the microhotplates, at ~24 mW of power consumption. Measurement results demonstrate that the fabricated sensors exhibit good sensitivity and feature ultra-fast response times - as low as 1.2 seconds.

Recent work to create components for the miniaturization of optical coherence tomography (OCT) systems is presented. The proposed approach relies on the micro-fabrication of microelectromechanical systems (MEMS) electrostatic actuators with integrated optical components onto the same die. This can enable very compact and cost effective components that have the potential of reducing the cost and form-factor of OCT systems. In this paper, the progress on two integrated OCT subsystems is presented: a continuously-variable optical delay line and a wavelength-swept filter. These components are suitable to implement time-domain or frequency-domain OCT, respectively. The integrated rapidly tunable optical delay line is based on a laterally rotating MEMS micro-mirror, while the swept filter is based on a rotating MEMS micro-motor.

This work introduces a novel dodecagon bulk mode gyroscope structure with parallel plate comb drives. A major contribution, compared to prior art, is that adding combs connected to the central disk structure, at the points of maximum vibration amplitudes, increases the drive strength and results in significant improvement in sensitivity. This can enable the fabrication of high performance bulk-mode gyroscopes in standard commercial MEMS technologies. Prototypes were measured to operate at frequencies of ~1.5 MHz, with quality factors of ~33,000, at a 10 mTorr vacuum level. Preliminary measurements using discrete electronics show a rate sensitivity of 0.31 μV/°/sec, corresponding to a capacitance sensitivity of 0.43 aF/°/sec/electrode.

This paper reports on the design and suggested fabrication steps of a bulk mode dodecagon disk gyroscope. A major contribution of this work, compared to prior art, is that it enables the fabrication of this important class of gyroscopes in commercially available and low-cost SOI technologies — e.g. MEMSCAP's SOIMUMPs. The structure was simulated using COMSOL, operates at 8.14 MHz, and exhibits a competitive rate sensitivity of ∼2.3 pA/°/s, a high dynamic range of 2000°/s, and a mechanical noise of 1°/√hr, for a quality factor of 10,000.

A MEMS bulk micromachined vibratory gyroscope is designed and fabricated in a commercial and low-cost SOI technology — MEMSCAP SOIMUMPs. The device was carefully designed to mitigate micro-fabrication limitations, while achieving high performance. Theoretical analysis of the drive and sense modes was performed in order to reduce the crosstalk between them, while still using a simple gyro structure. The device was simulated using COMSOL taking into account the anisotropic elastic properties of the ‘100’ single-crystalline silicon device layer for added accuracy. The gyroscope operates at 35 kHz with a 5 V DC bias voltage. The relatively low bias voltage leads to significant simplifications in the design of the biasing circuitry, and results in lower power consumption and electrical noise, while ensuring compatibility with standard integrated circuits technologies. The device exhibits a simulated rate sensitivity of ∼ 3 aF/°/s, and its theoretical mechanical noise is calculated to be 0.6 °/√hr. Measurements show a resonance frequency of 27.5 kHz and a quality factor of 120,000 at a 10 mTorr level of vacuum.

A CMOS variable gain driving circuit with output signal amplitude control for gyroscopes with wide range of quality factors is presented. The driving circuit can be used for gyroscopes with Q values higher than 500. The circuit uses a current-commutating switching mixer to control the gyroscope driving signal level. Conventional driving circuits use automatic gain control (AGC) which suffers from limited linear range and the need for an off-chip capacitor for the peak detector and loop filter. Two stage variable gain amplifier is used in the proposed design to ensure enough gain for oscillation for such a wide range of quality factors. Analog and digital amplitude control methods are used to cover wide range of driving signal amplitude with enough accuracy to hit the maximum driving signal level without sacrificing gyroscope linearity. Due to the high DC gain of the amplifier chain, DC offset resulting from mismatches might saturate the amplifier output. DC offset correction is employed using a secondary negative feedback loop. The proposed driving circuit is being fabricated in 0.6µm CMOS technology.

In this work, a complete single-ended readout circuit for capacitive MEMS gyroscope using chopper stabilization technique is presented. A novel noise cancellation technique is used to get rid of the bias noise. The circuit offers superior performance over state of the art readout circuits in terms of cost, gain, and noise for the given area and power consumption. The full circuit exhibits a gain of 58dB, a power dissipation of 1.3mW and an input referred noise of 12nV/√Hz. This would significantly improve the overall sensitivity of the gyroscope. The full circuit has been fabricated in 0.6µm CMOS technology and it occupies an area of 0.4mm × 1mm.