Projects

FUSED QUARTZ DUAL SHELL RESONATOR

In this project, a novel dual shell architecture for the fabrication of 3D Fused Quartz (FQ) resonators is demonstrated. The structure of the resonator consists of two FQ shells, fabricated concurrently using high-temperature glassblowing.  The inner shell is free to vibrate in its fundamental wineglass resonance mode. The outer shell in anchored to the substrate, providing a protective housing as well as double-anchor for the vibrating shell. The fixed-fixed anchor of the dual shell structure would improve the high-g shock survivability A finite element model of dual shell glassblowing was developed in this project to predict the final geometry of the resonators under different process parameters. The fabrication process is developed for the FQ dual shell and the substrate for the electrostatic operation. The presented dual shell architecture can be potentially implemented as a core sensing element of 3D shell microresonators and gyroscopes operating through shock and vibration. This project is part of DARPA AIMS program.

• Related publication:

1. Asadian, Mohammad H.; Shkel, Andrei; Fused Quartz Dual Shell Resonator, IEEE Inertial, Naples, FL, April 2019.
2. Shkel, Andrei; Asadian, Mohammad H.; Fused Quartz Dual Shell Resonator and Method of Fabrication, UC Case number 2019-670

Multi-Degrees-of-Freedom SOI MEMS gyroscopes

Multi-mass MEMS gyroscopes can be configured to improve sensitivity, bandwidth, and vibration immunity. The MEMS vibratory gyroscopes with two (or more) coupled masses and operating in the anti-phase resonance mode, would mitigate the energy dissipation through the substrate by balancing the total forces and moments acting on the anchors. Thus, dynamically balanced designs improve the quality factor, resulting in a higher sensitivity and improved in-run noise performance.

Another multi-mass MEMS gyroscope configuration, where the two (or more) non-identical masses are mechanically couples using non-identical spring elements, can mechanically amplify the amplitude of the vibration on the drive axis, improving the signal to noise ratio and increasing sensitivity. The mechanical amplification of amplitude would allow large drive amplitude on the sensing mass (slave) while the driving mass amplitude is within the linear regime of parallel-plate actuation. The mechanical amplification factor can be designed by selection of mass and stiffness parameters.

• Mode-ordered Dual Foucault Pendulum Gyroscope: In this project, a new tuning-fork type dual mass gyroscope was designed and fabricated using Stanford EpiSeal process. A new suspension mechanism was implemented to order the resonance modes of a previously designed Dual Foucault Pendulum (DFP). The structure of Mode-order DFP provided high stiffness and damping symmetry as well as high Q-facor. An exceptional Q-factor of over 1 million, which is in strong agreement with predictions of the TED model, was measured on a vacuum sealed prototype at room temperature. The measurement at low temperature, using a cryogenic probe station, made the anchor loss limit of Q-factor observable. A Q-factor of over 9 million was measured at 110K. The unbalanced electrostatic softening was identified experimentally as the contributing factor to the anchor loss. An electrostatic actuation model with capacitive gap mismatch predicted the unbalanced anti-phase motion of the proof masses. The anchor loss simulation predictions showed a strong dependence of the Q-factor to the unbalanced motion of the masses. The sensitivity of the Q-factor to stiffness unbalance was analyzed to identify the primary energy dissipation mechanisms at different temperatures. The initial open-loop rate gyro characterization results revealed ARW of 0.075 deg/rt-hr and in-run bias stability of 1.9 deg/hr, without temperature control in the lab environment.

• Related publications:

1. Asadian, Mohammad H.; Askari, Sina; Wang, Yusheng; Shkel, Andrei; Characterization of Energy Dissipation Mechanisms in Dual Foucault Pendulum Gyroscopes, IEEE Inertial, Naples, FL, April 2019.
2. Vatanparvar, Daryosh; Asadian, Mohammad H.; Askari, Sina; Shkel, Andrei; Characterization of Scale Factor Nonlinearities in Coriolis Vibratory Gyroscopes, IEEE International Symposium on Inertial Sensors and Systems, Naples, FL, April 2019.
3. Asadian, Mohammad H.; Askari, Sina; Flader, Ian B.; Chen, Yunhan; Gerrard, Dustin D.; Shin, Dongsuk D.; Kwon, Hyun-Keun; Kenny, Thomas W.; Shkel, Andrei; High Quality Factor Mode Ordered Dual Foucault Pendulum Gyroscope, IEEE Sensors Conference, New Delhi, India, October 2018. [PDF] [IEEE Xplore]

• Quad Mass Gyroscopes: Quad Mass Gyroscope (QMG) is another dynamically balanced MEMS gyroscope. The sensor structure consists of four identical proof masses and its suspension design provides a coupling between masses resulting in the anti-phase motion of four masses as the first resonance mode. The structure of QMG provides two structurally decoupled, identical, and orthogonal tuning fork resonators. The design and operation of QMG had been demonstrated in the past. In this project, new wafers were fabricated, characterized, and vacuum packaged to achieve the Thermoelastic Damping (TED) limit of the QMG design. Several sensors with Q-factor over 1.5 million were fabricated corresponding to the amplitude decay time constant over 300 seconds. A closed-loop rate-integrating mode of operation was demonstrated on a sensor with the Q-factor over 2 million. The effect of uncompensated quadrature error on the angular gain drift was analyzed. A model was developed to predict to the error in the angular gain for the different values of the quadrature error. This project was part of DARPA PASCAL program.

• Related publications:
  1. Askari, Sina; Asadian, Mohammad H.; Shkel, Andrei; Retrospective Correction of Angular Gain by Virtual Carouseling in MEMS Gyroscopes, IEEE International Symposium on Inertial Sensors and Systems, Naples, FL, April 2019.
  2. Askari, Sina; Asadian, Mohammad H.; Shkel, Andrei; High quality factor MEMS gyroscope with whole angle mode of operation, IEEE International Symposium on Inertial Sensors and Systems, Lake Como, Italy, March 2018.[IEEE Xplore]
  3. Asadian, Mohammad H.; Askari, Sina; Shkel, Andrei; An ultra-high vacuum packaging process demonstrating over 2 million Q-factor in MEMS vibratory gyroscopes, IEEE Sensors Letters, 1 (6), 2017, DOI 10.1109/LSENS.2017.2762287. [IEEE Xplore] [PDF]
  4. Askari, Sina; Asadian, Mohammad H.; Kakavand, Kasra; Shkel, Andrei M.; Vacuum sealed and getter activated MEMS Quad Mass Gyroscope demonstrating better than 1.2 million quality factor, IEEE International Symposium on Inertial Sensors and Systems, Laguna Beach, CA, March 2016. [IEEE Xplore]
  5. Askari, Sina; Asadian, Mohammad H.; Kakavand, Kasra; Shkel, Andrei M.; Near-navigation grade quad mass gyroscope with Q-factor limited by thermo-elastic damping, Solid-State Sensors, Actuators, and Microsystems Workshop, Hilton Head Island, South Carolina, USA, June 2016. [PDF]

• Dynamically Amplified MEMS Gyroscopes: Multi-degrees of freedom MEMS gyroscopes possess spurious vibration modes in addition to their mode of operation. As part of this project, a two-mass MEMS gyroscope was designed for Stanford EpiSeal fabrication process. Parametric modal analysis was performed using ANSYS Workbench to design the suspension of the two-mass system to (i) place the in-phase amplitude amplification mode as the lowest resonance mode and (ii) to increase the frequency separation between the in-phase operational mode and spurious tilt, out-of-plane, and rotation modes. The devices are currently under test. This project is part of DARPA AIMS program.

• Related publications:

1. Wang, Danmeng; Asadian, Mohammad H.; Efimovskaya, Alexandra; Shkel, Andrei M.; A Comparative Study of Conventional Single-Mass and Amplitude Amplified Dual-Mass MEMS Vibratory Gyroscopes, IEEE International Symposium on Inertial Sensors and Systems, Kauai, Hawaii, April 2017. [IEEE Xplore]

Fused Quartz Shell Resonator Gyroscope

Toward the realization of high performance, 3-D micro-machined rate integrating gyroscope, the University of California, Irvine is developing a new paradigm for wafer-level fabrication of inherently symmetric, atomically smooth, high Q-factor gyroscopes. The approach, pioneered by UC Irvine, uses surface tension and pressure driven micro-glassblowing process to form arrays of miniature high aspect ratio Fused Quartz (FQ) hemispherical shells with self-aligned stem structures. The fabrication process had been proposed and an FQ shell resonator at the operational frequency of 105 kHz had been demonstrated [7].  In this project, a modified fabrication process is proposed to fabricate low-frequency shell resonators. A broad range of shell thickness and radius was fabricated using the proposed method, with the wineglass resonance frequency from 5 kHz to 100 kHz. A finite element model for the glassblowing was developed to predict the final geometry of the shell resonators from the process parameters. Comprehensive finite element simulations were performed to explore the design space of the shell resonators operating at resonance frequencies lower than 20 kHz. It was demonstrated that mode separation and mode ordering at low-frequency shell resonators can be achieved through the design of the shell geometry. A novel assembly method was developed to form vertical capacitors with gaps of smaller than five microns, for electrostatic excitation and detection of wineglass modes. The electrostatic frequency tuning was simulated using COMSOL Multiphysics to predict the required capacitive gaps for frequency tuning, For the first time, the rate gyro operation was demonstrated on a FQ shell device with assembled electrodes. This project was part of DARPA MRIG program.

• Related publications:

1. Asadian, Mohammad H.; Wang, Yusheng; Shkel, Andrei; Development of 3D Fused Quartz Hemi-Toroidal Shells for High-Q Resonators and Gyroscopes, IEEE Journal of Microelectromechanical Systems (JMEMS), Vol. 28, No. 6, pp. 954-964, December 2019, [IEEE Xplore] [PDF]
2. Asadian, Mohammad H.; Noor, Radwan M; Shkel, Andrei; Simulation-Based Approach in Design of 3D Micro-Glassblown Structures for Inertial and Optical Sensors, IEEE Sensors, Montreal, QC, Oct. 2019. [PDF]
3. Asadian, Mohammad H.; Wang, Yusheng; Shkel, Andrei; Design space exploration of hemi-toroidal fused quartz shell resonators, IEEE Inertial, Naples, FL, April 2019.
4. Asadian, Mohammad H.; Wang, Yusheng; Shkel, Andrei; Design and Fabrication of 3D Fused Quartz Shell Resonators for Broad Range of Frequencies and Increased Decay Time, IEEE Sensors Conference, New Delhi, India, October 2018. [PDF]
5. Wang, Yusheng; Asadian, Mohammad H.; Shkel, Andrei; Modeling the Effect of Imperfections in Glassblown Micro-Wineglass Fused Quartz Resonators, Journal of Vibration and Acoustics, 139 (4), 8, 2017, The American Society of Mechanical Engineers [ASME]
6.  Asadian, Mohammad H.; Wang, Yusheng; Askari, Sina; Shkel, Andrei; Controlled Capacitive Gaps for Electrostatic Actuation and Tuning of 3D Fused Quartz Micro Wineglass Resonator Gyroscope, IEEE International Symposium on Inertial Sensors and Systems, Kauai, Hawaii, April 2017. [IEEE Xplore]
7.  Wang, Yusheng; Asadian, Mohammad H.; Shkel, Andrei; Frequency Split Reduction by Directional Lapping of Fused Quartz Micro Wineglass Resonators, IEEE International Symposium on Inertial Sensors and Systems, Kauai, HI, April 2017. [IEEE Xplore]
8.  Wang, Yusheng; Asadian, Mohammad H.; Shkel, Andrei M.; Predictive Analytical Model of Fundamental Frequency and Imperfections in Glassblown Fused Quartz Hemi-Toroidal 3D Micro Shells, IEEE Sensors, Orlando, FL, November 2016. [IEEE Xplore]
9.  Senkal, Doruk; Ahamed, Mohammed J.; Asadian Ardakani, Mohammad H.; Askari, Sina; Shkel, Andrei M.; Demonstration of 1 Million Q-Factor on Microglassblown Wineglass Resonators With Out-of-Plane Electrostatic Transduction, Journal of Micromechanical Systems (JMEMS), 24 (1), pp. 29-37, 2015. [IEEE Xplore]
10.  Senkal, Doruk; Ahamed, Mohammed J.; Asadian Ardakani, Mohammad H.; Askari, Sina; Shkel, Andrei M.; Out-of-plane Electrode Architecture for Fused Silica Micro-glassblown 3-D Wineglass Resonators, IEEE Sensors, Valencia, Spain, November 2014. [IEEE Xplore]

Ultra-Stable microTorr-Level Vacuum Packaging for High-Performance Inertial Sensors
Packaging is the final step in the process loop for the MEMS devices. The role of packaging MEMS devices is becoming increasingly important as the devices are getting more sophisticated. In the case of inertial MEMS devices, sub-mTorr vacuum level is required to effectively suppress the viscous damping and improve the quality factor. In this project, an optimized temperature profile was developed to achieve an ultra high level of vacuum inside the sealed package (sub-mTorr). The process was tuned to avoid any defect in the sealing area while providing enough time and temperature for appropriate solder reflow and getter activation. We used SST 3150 furnace for vacuum sealing process development. The results demonstrated ultra-high quality factor over 2 million on a quad mass gyroscope (QMG). This project was part of DARPA PASCAL program.

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• Related publications:

1. Asadian, Mohammad H.; Askari, Sina; Shkel, Andrei; An ultra-high vacuum packaging process demonstrating over 2 million Q-factor in MEMS vibratory gyroscopes, IEEE Sensors Letters, 1 (6), 2017, DOI 10.1109/LSENS.2017.2762287. [IEEE Xplore]

Deformation Analysis of Lightweight Dissimilar Metallic Sheets

In this project, two different consolidation methods for manufacturing of composite metallic sheets were performed. In one method, the dissimilar blanks were tailored using a welding step. These blanks are called Tailor-Welded Blanks (TWB). TWB offers functional strengthening using stiffer/thicker blanks at the location of higher stress or impact while using lighter/thinner where no such high stress is expected. In another way, the dissimilar metallic sheets were bonded using an adhesive to form a two-ply metallic sheet. The plastic deformation mechanism in dissimilar sheet metals is more complex compared to a homogenous sheet. In the project, different failure mechanisms in the forming of parts from composite metallic blanks were studied. The common mechanisms are spring-back after bending and wrinkling after a deep drawing in the laminated sheets, and weld-line movement in TWBs. The different failure mechanisms in the forming of parts from composite metallic blanks were studied.  Analytical and numerical models for the analysis of stress and strain during the plastic deformation of composite sheet metals were developed. The models were developed to find the metal forming process parameters to reduce the wrinkling and spring back in the two-ply sheet metals and weld-line movement in tailor-welded metal sheets.

• Related publications:

1. Asadian-Ardakani, Mohammad Hossein; Morovvati, Mohammad Reza; Mirnia, Mohammad Javad; Dariani, Bijan Mollaei; Theoretical and experimental investigation of deep drawing of tailor-welded IF steel blanks with non-uniform blank holder forces, Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 231 (2), pp.286-300, 2015. [PDF]
2. Morovvati, MR; Mollaei-Dariani, B; Asadian-Ardakani, MH; A theoretical, numerical, and experimental investigation of plastic wrinkling of circular two-layer sheet metal in the deep drawing, Journal of Materials Processing Technology, 210 (13), pp.1738-1747, 2010. [Elsevier]
3. Adibi, Hamed; Asadian Ardakani, Mohammad H; Mollaei-Dariani, Bijan; Springback Analysis of Sheet Metal Laminates After U-bending, Metal 2010, Brno, Czech Republic, May 2010. [PDF]

 

Joule Heating of Carbon Nanowires for Local Chemical Vapor Deposition and Controlled Nanowire Thinning
Joule heating was utilized for local chemical vapor deposition (CVD) and controlled thinning of SU8-driven carbon nanowires for various sensor and nano-electronic applications. To illustrate the feasibility of the proposed method, the carbon nanowires (CNWs) suspended between carbon MEMS electrodes were heated for the deposition of tungsten oxide (WO3) film by decomposing tungsten hexacarbonyl [W(CO)6]. With this local CVD technique, one can deposit any desired material from a volatile precursor, selectively onto the CNWs. The controlled thinning method one can fabricate nanojunctions without the need for expensive, vacuum-based equipment.