Project 1

High-Velocity MEMS Resonator Development – UT Dallas

Inspired by DARPA's initiative to develop ultra-fast resonant microsystems for enhanced MEMS gyroscope performance, I designed, simulated, fabricated, and tested MEMS resonators at the University of Texas at Dallas capable of reaching extreme vibrational velocities. Despite conservative initial expectations, the devices performed exceptionally well—achieving peak velocities exceeding 30 m/s (over 108 km/h) at resonant frequencies up to 28 kHz.

Visualizing such motion in a scanning electron microscope (SEM) proved challenging; however, motion artifacts were discernible, with vibration amplitudes reaching several hundred microns. Peak tip accelerations surpassed 0.5 million-g  , generating internal stress levels exceeding 1 GPa, which led to mechanical failure in designs with sharp geometry. In contrast, a redesigned 11 kHz device featuring rounded corners remained intact up to 35 m/s, limited only by the capabilities of the driving circuit and the imaging resolution of the SEM.

High aspect ratio polysilicon and single crystalline silicon (HARPSS) 

Project 2

HARPSS-Based MEMS Fan 

• Designed and developed MEMS cooling fans using high-frequency resonant actuation, aimed at enhancing heat dissipation in compact electronic systems.

• Employed a 6-mask HARPSS process, including two LPCVD nitride layers, one polysilicon deposition, and deep cavity etching to form suspended membranes with high aspect-ratio air gaps.

• Fabricated 3 mm × 4 fan arrays per chip, each with parallel membranes suspended above 5–10 µm cavities and two distinct airgap configurations (300 nm and 500 nm).

• Achieved resonance frequencies between 400–700 kHz, with measured displacements of ~1.3 µm and tip velocities of 2 m/s at 50 V AC, demonstrating effective air pumping at microscale.
  
  

Microvision Resonator Fabrication

• Designed and fabricated high-performance MEMS resonators with a multi-level structural architecture to enable large amplitude oscillations and enhanced frequency stability.

• Utilized a 4-mask process including hard mask deposition and patterning, with 3-level alignment and etching to realize the complex structure.

• Achieved deep reactive ion etching (DRIE) up to ~500 µm to form high-aspect-ratio trenches while effectively mitigating aspect-ratio-dependent etching (ARDE) issues to maintain trench fidelity.

• Explored and implemented multiple resonator geometries for performance optimization across different operating conditions.

Project 4

MEMS Finger Fan Design

• Designed a novel micro-scale fan utilizing a lateral electrostatic comb-drive actuator fabricated on an SOI wafer, targeting compact and efficient thermal management applications.

• Utilized a 40 µm device layer on SOI with 2 µm LPCVD silicon nitride for structural insulation and mechanical integrity.

• Tuned resonance to ~900 kHz using COMSOL Multiphysics simulations, optimizing vibrational performance for efficient air movement at high frequencies.

• Integrated parallel comb electrodes to enhance electrostatic driving force and air pumping efficiency.

• Optimized electrode geometry to maximize in-plane displacement and tip velocity, improving airflow generation within microscale constraints.

Project 5

MEMS Fan Cooling Simulation

• Simulated convective heat transfer to evaluate the thermal performance of the fabricated MEMS fans in dissipating heat from a hot silicon chip.

• Modeled 3.5 W of localized heat dissipation with 60 cc/s airflow across the chip surface, accounting for flow dynamics and fan-induced velocity profiles.

• Results confirmed that high-frequency MEMS fan operation could significantly lower chip surface temperatures, validating the system’s potential for on-chip cooling in densely packed microelectronic devices.
  
  

Project 7 & 8

                      Actuator for moving a stage         Mirror  actuation designm(HARPSS) 

Project 9

Project 10

Copper Patterning on PCB with Wet Etching

• Deposited and patterned 5 µm copper layers on a PCB with a large, uneven surface, overcoming challenges related to topographical non-uniformity.

• Defined 500 µm-wide copper features using photolithography and performed wet etching to selectively remove unwanted copper, ensuring clean pattern definition.

• Optimized process parameters to accommodate etch rate variation across uneven surfaces, achieving consistent feature quality and adhesion.

Project 11

(my PhD project)

Design and Analysis of a Rotating Broadband Energy Harvesting System with Auxetic Resonator for Installation on Train Axis 

This project investigates a novel approach to enhance the efficiency of piezoelectric energy harvesters in rotating systems, particularly focusing on the application for freight train axles. The goal is to provide power for self-powered sensors by utilizing the auxetic meta-structure concept to improve the performance of resonators. The energy harvester design consists of a cantilever or bistable clamped-clamped buckled beam with a tip mass, a piezoelectric patch, and a latticed substrate.

Three distinct auxetic patterns are proposed and implemented on the base of the cantilever or buckled beam to increase the harvested power. Finite Element Modeling (FEM) is employed to optimize the geometrical parameters of the auxetic designs and examine their effects on the resonator’s output power. Experimental validation is performed at rotational frequencies matching the operational speeds of freight train axles.

Two substrate materials—aluminum and steel—are used to fabricate the resonators, and various piezoelectric materials (PZT types) are examined. The bistable resonator design shows particular promise, as its bistability leads to enhanced efficiency over a wide frequency range, reducing reliance on resonance frequency tuning. For the bistable Auxetic-I harvester (AEH-I), the energy conversion efficiency reaches 45.9%, with significant output power amplification.

Overall, the auxetic resonators demonstrate magnification factors between 2.14 and 11.13, depending on the auxetic design and substrate material. Both numerical and experimental results show that auxetic meta-structures can substantially increase the efficiency of rotary energy harvesting systems for applications such as freight train axle power generation.

Project 12

(my master project)

Design and Manufacturing of an Equipment for Ride Comfort Measurement in High-speed Trains Using Micro Electromechanical Sensors 

Rail surface irregularities are one of the most influential factors in the performance of rail fleets, particularly in passenger services. On the other hand, due to economic considerations and the need to reduce travel time, the demand for increased speed in rail transportation is inevitable. Feasibility studies to meet this demand involve a comprehensive process, including assessing track quality, the impact of speed on the dynamic performance of rail vehicles and their interaction with the track, the effect of speed on vehicle stability, travel safety, passenger comfort, fleet lifespan, and more.

Track surface irregularities, being inherently random, significantly influence the dynamic movement of the train. These irregularities induce vibrations in the moving train, which can substantially reduce the lifespan of rail components due to fatigue loading and affect passenger comfort. Measuring, monitoring, and analyzing the accelerations experienced by the rail vehicles and passengers are essential for calculating the ride comfort index, which is determined by various standards such as ISO, UIC, CEN, the UK Railway Motion Index, and engineering criteria like the Sperling Index (Wz).

In this project, we first study ride comfort based on the CEN standard in Europe. Then, using Arduino and a MEMS 3-axis accelerometer, we design and build a device to measure and monitor these accelerations. For user convenience, a graphical interface tailored to ride comfort measurements is developed using LabVIEW software. Two tests were conducted on Line 1 of the Tehran Metro, between Baqer Shahr and Shahr-e Rey stations, to measure ride comfort, and the effectiveness of the device was successfully demonstrated.

Project 13

(Fankavan Aral group Projects)

Integrated Train Monitoring System (ITMS)

Integrated Train Monitoring System (ITMS) is a powerful solution to continually monitor train safety critical parameters. With a modular, specification-compliant design that integrates seamlessly with new or existing train equipment, our ITMS provides an intuitive, centralized system for operators and maintainers.

Project 14

(Fankavan Aral group Projects)

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