Digital Commons Network^™

Employing Boundary Element Approach With Genetic Algorithm To Increase Travel Range Of Repulsive Actuators, Yu Tian, Ronald N. Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

The design of repulsive electrostatic actuators having enlarged travel range is achieved by combining the boundary element approach and a genetic algorithm. The boundary element method enables calculating the electrostatic forces without time consuming finite element simulations. Once a static equation that uses a model of effective lumped mass solves the travel ranges, the GA maximizes travel ranges by optimizing the dimensional parameters. The effectiveness of the scheme is demonstrated with extensive experimental results showing the travel ranges of a micro out-of-plane actuator are increased by up to 190%. The developed platform can improve the signal-to-noise ratios and the performance …

A Mems Pressure Sensor Using Electrostatic Levitation, Mohammad Mousavi, Mohammad Alzgool, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Applying electrostatic levitation force to the initially-closed gap-closing electrodes of our micro-electro- mechanical system (MEMS) creates multi actuation mechanisms, and opens a new world to the MEMS applications.

Electrostatic levitation allows us to measure physical quantities, such as air pressure, by exploiting pull-in instability and releasing. The beam starts from a pulled-in position by applying a voltage difference between two gap-closing electrodes. When enough voltage is applied to the side electrodes, the cantilever beam is released. At the release instant, electrostatic forces, restoring force, and surface force are applied to the cantilever. According to the experimental results of this work, …

Electrostatic Levitation: An Elegant Method To Control Mems Switching Operation, Mohammad Mousavi, Mohammad Alzgool, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

This paper investigates the characteristics of a micro-switch that uses two side electrodes to open a normally closed switch. The side electrodes surround the xed electrode in the well-known gap-closing electrode configuration. The side electrodes can open a closed switch and be tuned to respond appropriately to outside forces. The combined electrode system dramatically improves the control of a standard gap-closing electrode configuration. In conventional switches, a DC voltage above a certain value closes the switch. To re-open the switch, the voltage difference is reduced to peel o the moving electrode. Currently the contact area is carefully designed to avoid …

Autonomous Shock Sensing Using Bi-Stable Triboelectric Generators And Mems Electrostatic Levitation Actuators, Mohammad Mousavi, Mohammad Alzgool, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

This work presents an automatic threshold shock-sensing trigger system that consists of a bi-stable triboelectric transducer and a levitation-based electrostatic mechanism. The bi-stable mechanism is sensitive to mechanical shocks and releases impact energy when the shock is strong enough. A triboelectric generator produces voltage when it receives a mechanical shock. The voltage is proportional to the mechanical shock. When the voltage exceed a certain level, the initially pulled-in Microelectromechanical system (MEMS) switch is opened and can disconnect the current in a safety electronic system. The MEMS switch combines two mechanisms of gap-closing (parallel-plate electrodes) with electrostatic levitation (side electrodes) to …

Feasibility Study Of A Micro-Electro-Mechanical-Systems Threshold-Pressure Sensor Based On Parametric Resonance: Experimental And Theoretical Investigations, Mark Pallay, Meysam Daeichin, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

A tunable threshold pressure sensor based on parametric resonance of a microbeam subjected to electrostatic levitation is proposed. Parametric excitation can trigger a large amplitude vibration at twice the natural frequency if the magnitude of the driving force is large enough to overcome energy loss mechanisms in the system such as squeeze film damping. This causes a temporarily unstable response with a significant gain in oscillation amplitude over time until it is eventually capped by nonlinearities in the force or material or geometric properties. The instability divides the frequency region into two regions: distinct responses bounded by the system non-linearity, …

Characterization Of A Packaged Triboelectric Harvester Under Simulated Gait Loading For Total Knee Replacement, Nabid Aunjum Hossain, Geofrey George Yamomo, Ryan Willing, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Load sensing total knee replacement (TKR) implants are useful tools for monitoring prosthesis health and providing quantitative data to support patient claims of pain or instability. Powering such devices throughout the entire life of the knee replacement, however, is a challenge, and selfpowered telemetry via energy harvesting is an attractive solution. Herein, we implemented vertical contact mode triboelectric energy harvesters inside a knee implant package to generate the power required for embedded digitization and communications circuitry. The harvesters produce small-scale electric power from physiologically relevant loads transmitted through the knee. Experiments were performed on a joint motion simulator with an …

Feasibility Study Of A Mems Threshold-Pressure Sensor Based On Parametric Resonance: Experimental And Theoretical Investigations, Mark Pallay, Meysam Daeichin, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

A tunable threshold pressure sensor based on para- metric resonance of a microbeam subjected to electrostatic levitation is proposed. Parametric excitation can trigger a large amplitude vibration at twice the natural frequency if the mag- nitude of the driving force is large enough to overcome energy loss mechanisms in the system such as squeeze film damping. This causes a temporarily unstable response with a significant gain in oscillation amplitude over time until it is eventually capped by nonlinearities in the force or material or geometric properties. The instability divides the frequency region into two regions: distinct responses bounded by the …

Large-Stroke Capacitive Mems Accelerometer Without Pull-In, Meysam Daeichin, Ronald Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

In this study, the feasibility of obtaining electrical read-out data from a capacitive MEMS accelerometer that employs repulsive electrode configuration is demonstrated. This configuration allows for large-stroke vibrations of microstructures without suffering from pull-in failure that exists in conventional accelerometers based on the parallelplate configuration. With initial fabrication gap of 2:75um, the accelerometer can reach a 4:2um dynamical displacement amplitude. The accelerometer is tested up to 95(V) without exhibiting pull-in failure. For comparison, the pull-in voltage of an accelerometer with same dimensions but with conventional parallel-plate electrode configuration is 0:8(V). The MEMS device is fabricated using the POLYMUMPs fabrication standard. …

Parametric Study Of A Triboelectric Transducer In Total Knee Replacement Application, Alwathiqbellah Ibrahim, Geofrey Yamomo, Ryan Willing, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Triboelectric energy harvesting is a relatively new technology showing promise for biomedical applications. This study investigates a triboelectric energy transducer for potential applications in total knee replacement (TKR) both as an energy harvester and a sensor. The sensor can be used to monitor loads at the knee joint. The proposed transducer generates an electrical signal that is directly related to the periodic mechanical load from walking. The proportionality between the generated electrical signal and the load transferred to the knee enables triboelectric transducers to be used as self-powered active load sensors. We analyzed the performance of a triboelectric transducer when …

Towards A High Bias Voltage Mems Filter Using Electrostatic Levitation, Mark Pallay, Ronald Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Traditional MEMS filters use a comb drive structure that suffers from the pull- in instability, which places a significant limitation on the achievable signal-to- noise ration of the sensor. Because the output signal from a capacitive sensor

is linearly related to the applied voltage, it is desirable to use a capacitive sensor that can withstand large voltages upwards of 100V. However, the pull-in instability causes high voltages to destroy the device and a trade-off between performance and reliability must be made. Electrostatic levitation, which works by pulling electrodes apart instead of together, eliminates the pull-in instability and allows for very …

Experimental Characterization Of The Electrostatic Levitation Force In Mems Transducers, Meysam Daeichin, Ronald Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

In this study, a two-step experimental procedure is described to determine the electrostatic levitation force in MEMS transducers. In these two steps, the microstructure is excited quasi-statically and dynamically and its response is used to derive the electrostatic force. The experimental results are obtained for a 1 by 1 plate that employs 112 levitation units. The experimentally obtained force is used in a lumped parameter model to find the microstructure response when it is subjected to different dynamical loads. The natural frequency and the damping ratios in the model are identified from the experimental results. The results show this procedure …

Lateral Pull-In Instability Of Electrostatic Mems Transducers Employing Repulsive Force, Meysam Daeichin, Ronald Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

We report on the lateral pull-in in capacitive MEMS transducers that employ a repulsive electrostatic force. The moving element in this system undergoes motion in two dimensions. A two degree-offreedom mathematical model is developed to investigate the pull-in quantitatively. The nonlinear electrostatic force, which is a vector function of two spatial coordinates, is determined by calculating the potential energy of the system using a boundary element approach. The equilibrium points are found by numerically solving the nonlinear coupled static equations. A stability analysis reveals that depending on the values of the lateral and transverse stiness, the system undergoes dierent bifurcations …

Modeling And Characterization Of A Pull-In Free Mems Microphone, Mehmet Ozdogan, Shahrzad Towfighian, Ronald Miles

Mechanical Engineering Faculty Scholarship

In this study, we examine the feasibility of designing a MEMS microphone employing a levitation based electrode configuration. This electrode scheme enables capacitive MEMS sensors that could work for large bias voltages without pullin failure. Our experiments and simulations indicate that it is possible to create robust sensors properly working at high DC voltages, which is not feasible for most of the conventional parallel plate electrode-based micro-scale devices. In addition, the use of larger bias voltages will improve signal-to-noise ratios in MEMS sensors because it increases the signal relative to the noise in read-out circuits. This study presents the design, …

Analysis Of Mechanical Deformation Eect On The Voltage Generation Of A Vertical Contact Mode Triboelectric Generator, Nabid Aunjum Hossain, Mir Jalil Razavi, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

One of the associated factors that controls the performance of a triboelectric generator (TEG) is the mechanical deformation of the dielectric layer. Therefore, a good contact model can be a prominent tool to find a more realistic and efficient way of determining the relationships between the contact and electrical output of the generator. In this study, experiments are conducted on a vertical contact mode triboelectric generator under an MTS machine. The open-circuit voltages are measured at different loads imposed by the MTS by controlling the cyclic displacement of the top tribo layer of the generator. A finite-element-based theoretical model is …

Pairing Electrostatic Levitation With Triboelectric Transduction For High-Performance Self-Powered Mems Sensors And Actuators, Mark Pallay, Alwathiqbellah I. Ibrahim, Ronald N. Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

We demonstrate that an electrostatic levitation MEMS switch can be operated by applying mechanical pres- sure to a triboelectric generator. The toggling mechanism of the switch draws no current but requires a high actuating voltage, while the generator can supply a high voltage but only produces microwatts of power. The synergistic combination results in an entirely self-powered sensor and switch; the normally-closed MEMS switch can be toggled open by applying a threshold force to the generator without the need for any outside power or supplementary circuitry. A model of the MEMS switch and electrostatic force is validated with experimental data. …

Merging Parallel-Plate And Levitation Actuators To Enable Linearity And Tunability In Electrostatic Mems, Mark Pallay, Ronald N. Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

In this study, a linear electrostatic MEMS actuator is introduced. The system consists of a MEMS cantilever beam with combined parallel-plate and electrostatic levitation forces. By using these two forcing methods simultaneously, the static response and natural frequency can be made to vary linearly with the voltage. The static response shows a linear increase of 90 nm/V and is maintained for more than 12μm of the tip displacement. The natural frequency shows a linear increase of 16 Hz/V and is maintained throughout a 2.9 kHz shift in the natural frequency. This wide range of linear displacement and frequency tunability is …

A Parametric Resonator With Low Threshold Excitation For Vibration Energy Harvesting, Shahrzad Towfighian, Wei Yang

Mechanical Engineering Faculty Scholarship

A parametric resonator for vibration energy harvesting is presented. Despite large responses from parametric resonance, two major drawbacks of parametric resonance harvesters are the high threshold excitation and narrow bandwidth. We addressed these two shortcomings by adding magnetic nonlinearity to the system. The proposed vibration energy harvester consists of two piezoelectric cantilevers beams, each with a magnetic tip. By controlling the distance between the two magnets, the threshold excitation level needed to trigger the parametric resonance decreases. Combining the softening and hardening behavior of the two magnetically coupled beams increases the frequency bandwidth. In addition, the amplitude of the response …

Dynamic Response Of A Tunable Mems Accelerometer Based On Repulsive Force, Meysam Daeichin, Mehmet Ozdogan, Shahrzad Towfighian, Ronald Miles

Mechanical Engineering Faculty Scholarship

This paper describes a tunable MEMS electrostatic accelerometer that uses repulsive electrode configuration so that the design is not hampered by capacitive pull-in instability. The repulsive force configuration enables the increase of DC bias voltage without suffering from the pull-in failure mode. This flexibility in increasing voltage can be employed as a tuning parameter to widen the working frequency range and to improve the robustness of the accelerometer. A lumped parameter model is developed to simulate the response of the microstructure under a combination of electrostatic and dynamic mechanical loading. The electrostatic force is estimated using a finite element simulation. …

A Smart Knee Implant Using Triboelectric Energy Harvesters, Shahrzad Towfighian, Alwathiqbellah Ibrahim, Manav Jain, Emre Salman, Ryan Willing

Mechanical Engineering Faculty Scholarship

Although the number of total knee replacement (TKR) surgeries is growing rapidly, functionality and pain-reduction outcomes remain unsatisfactory for many patients. Continual monitoring of knee loads after surgery offers the potential to improve surgical procedures and implant designs. The goal of this study is to characterize a triboelectric energy harvester under body loads and to design compatible frontend electronics to digitize the load data. The harvester prototype would be placed between the tibial component and polyethylene bearing of a TKR implant. The harvester generates power from the compressive load. To examine the harvester output and the feasibility of powering a …

Dynamics Of A Threshold Shock Sensor: Combining Bi-Stability And Triboelectricity, Daniel S. Nelson, Alwathiqbellah Ibrahim, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

A proof of concept of a triboelectric threshold shock sensor and its characterization are presented. Shock sensors are used in many applications in the automotive, shipping and other industries, mainly to determine if acceleration thresholds are met. Many shock sensors are only mechanical, so the only way to know if the threshold has been reached is to physically check the device. There are noticeable advantages of using triboelectric transduction and bi-stability to create a shock sensor. By combining a buckled-beam structure and a triboelectric generator, we created a proof of concept of a tunable threshold shock sensor. The sensor generates …

A Tunable Electrostatic Mems Pressure Switch, Mark Pallay, Ronald N. Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

We demonstrate a tunable air pressure switch. The switch detects when the ambient pressure drops below a threshold value and automatically triggers without the need for any computational overhead to read the pressure or trigger the switch. The switch exploits the significant fluid interaction of a MEMS beam undergoing a large oscillation from electrostatic levitation to detect changes in ambient pressure. If the oscillation amplitude near the resonant frequency is above a threshold level, dynamic pullin is triggered and the switch is closed. The pressure at which the switch closes can be tuned by adjusting the voltage applied to the …

A Reliable Mems Switch Using Electrostatic Levitation, Mark Pallay, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

In this study an electrostatic MEMS beam is experimentally released from pull-in using electrostatic levitation. A MEMS cantilever with a parallel plate electrode configuration is pulled-in by applying a voltage above the pull-in threshold. Two more electrodes are fixed to the substrate on both sides of the beam to create electrostatic levitation. Large voltage pulses upwards of 100 V are applied to the side electrodes to release the pulled-in beam. A high voltage is needed to overcome the stronger parallel plate electrostatic force and stiction forces, which hold the beam in its pulled-in position. A relationship between bias voltage and …

A Parametric Electrostatic Resonator Using Repulsive Force, Mark Pallay, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

In this paper, parametric excitation of a repulsive force electrostatic resonator is studied. A theoretical model is developed and validated by experimental data. A correspondence of the model to Mathieu's Equation is made to prove the existence and location of parametric resonance. The repulsive force creates a combined response that shows parametric and subharmonic resonance when driven at twice its natural frequency. The resonator can achieve large amplitudes of almost 24 μm and can remain dynamically stable while tapping on the electrode. Because the pull-in instability is eliminated, the beam bounces off after impact instead of sticking to the electrode. …

Parametric Resonance Of A Repulsive Force Mems Electrostatic Mirror, Mehmet Ozdogan, Meysam Daeichin, Abdallah H. Ramini, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

We investigate the nonlinear dynamic behavior of an electrostatic MEMS mirror. The MEMS mirror is driven by repulsive force actuators, which avoid pull-in instability and enable large travel ranges. In parallel-plate actuators, the force on the structure is toward the substrate limiting the range of motion to the capacitor gap. Unlike parallel-plate, repulsive force actuators push the mirror away from the substrate not limiting the motion. The highly nonlinear nature of the repulsive force and the large motions create unique characteristics that dier from parallel-plate actuators. Repulsive force actuators show linear natural frequency hardening with increased DC voltages unlike parallel-plate …

A Hybrid Nonlinear Vibration Energy Harvester, Wei Yang, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Vibration energy harvesting converts mechanical energy from ambient sources to electricity to power remote sensors. Compared to linear resonators that have poor performance away from their natural frequency, nonlinear vibration energy harvesters perform better because they use vibration energy over a broader spectrum. We present a hybrid nonlinear energy harvester that combines bi-stability with internal resonance to increase the frequency bandwidth. A two-fold increase in the frequency bandwidth can be obtained compared to a bi-stable system with fixed magnets. The harvester consists of a piezoelectric cantilever beam carrying a movable magnet facing a fixed magnet. A spring allows the magnet …

Magnetoelastic Beam With Extended Polymer For Low Frequency Vibration Energy Harvesting, Alwathiqbellah Ibrahim, Shahrzad Towfighian, Mohammad I. Younis, Quang Su

Mechanical Engineering Faculty Scholarship

Ambient energy in the form of mechanical kinetic energy is mostly considered waste energy. The process of scavenging and storing such energy is known as energy harvesting. Energy harvesting from mechanical vibration is performed using resonant energy harvesters (EH) with two major goals: enhancing the power scavenged at low frequency sources of vibrations, and increasing the efficiency of scavenging energy by increasing the bandwidth near the resonant frequency. Toward such goals, we propose a piezoelectric EH of a composite cantilever beam with a tip magnet facing another magnet at a distance. The composite cantilever consists of a piezoelectric bimorph with …

Nonlinear Vibration Energy Harvesting Based On Variable Double Well Potential Function, Wei Yang, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Converting ambient mechanical energy to electricity, vibration energy harvesting, enables powering of the low-power remote sensors. Nonlinear energy harvesters have the advantage of a wider frequency spectrum compared to linear resonators making them more efficient in scavenging the broadband frequency of ambient vibrations. To increase the output power of the nonlinear resonators, we propose an energy harvester composed of a cantilever piezoelectric beam carrying a movable magnet facing a fixed magnet at a distance. The movable magnet on the beam is attached to a spring at the base of the beam. The spring-magnet system on the cantilever beam creates the …

A Cylindrical Triboelectric Energy Harvester For Capsule Endoscopes, Lejie Liu, Shahrzad Towfighian, Zhanpeng Jin

Mechanical Engineering Faculty Scholarship

Capsule endoscopy is a new technology that has the potential to replace conventional endoscopy in the near future due to its non-invasive nature. A major limitation for their functionality is the limited battery life. We have investigated a triboelectric energyharvester inside a capsule endoscope that can generate power from natural contractions of gastrointestinal (GI) tract. The periodic contacts and separations of two triboelectric materials inside the capsule endoscope create an alternating current that can be used to charge the capsule endoscope battery, which is used for imaging the GI tract. This study presents an analytical closed form solution for the …

A Review Of Locomotion Systems For Capsule Endoscopy, Lejie Liu,, Shahrzad Towfighian, Amine Hila

Mechanical Engineering Faculty Scholarship

Wireless capsule endoscopy for gastrointestinal (GI) tract is a modern technology that has the potential to replace conventional endoscopy techniques. Capsule endoscopy is a pill-shaped device embedded with a camera, a coin battery, and a data transfer. Without a locomotion system, this capsule endoscopy can only passively travel inside the GI tract via natural peristalsis, thus causing several disadvantages such as inability to control and stop, and risk of capsule retention. Therefore, a locomotion system needs to be added to optimize the current capsule endoscopy. This review summarizes the state-of-the-art locomotion methods along with the desired locomotion features such as …

Mega: An Energy Aware Algorithm For Self-Powered Wireless Sensor Networks In Sustainable Smart Infrastructure, Dong Qi, Yu Chen, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Smart infrastructure is attractive for possessing many desirable features, such as uninterrupted monitoring of health conditions, timely response to damages, and human-infrastructure interactions. Embedded sensors that collectinformation are critical for decision making. However, the lifetime of electronic sensors is a constraint to infrastructure lifetime if sensors are physically embedded in the infrastructure at construction time. In this paper, we studied a self-powered wireless sensor network that harvests energy from mechan-ical vibration in the environment. A dynamic, hierarchical algorithm called MEGA is proposed that constructs clusters and elects the cluster head based on residue energy and energy harvest rate. Taking a …