Modeling Of Structural And Environmental Effects On Microelectromechanical (Mems) Vibratory Gyroscopes

In this paper we investigate the effects of stiffness, damping and temperature on the performance of a MEMS vibratory gyroscope. The stiffness and damping parameters are chosen because they can be appropriately designed to synchronize the drive and sense mode resonance to enhance the sensitivity and stability of MEMS gyroscope. Our results show that increasing the drive axis stiffness by 50% reduces the sense mode amplitude by ~27% and augments the resonance frequency by ~21%. The stiffness and damping are mildly sensitive to typical variations in operating temperature. The stiffness increases by 1.25%, while the damping decreases by 3.81%, when the temperature is raised from 0C to 45C. Doubling the damping reduces the oscillation amplitude by 80%, but ~1% change in the frequency. The predicted effects of stiffness, damping and temperature can be utilized to design a gyroscope for the desired operating condition

Optimization of Interaural Intensity Difference based Binaural Sonar Sensing System for Object Detection

Interaural Intensity Difference (IID) in binaural sonar systems is used for echolocation and obstacle sensing. In this article, we show by simulation the optimized system’s parameters in terms of frequency, sensor separation distance and the working range for an IID based binaural sonar sensing system. Our result shows that the best performances with a frequency range between 100 to 300 kHz and a separation distance, depending on the size of the microphone, in our case between 2 cm to 5 cm within the working range of 1 m. The approach developed in this paper could be useful for mobile localization and mapping, particularly in compact size mobile devices

Design of a Microfluidic Based Lab-on-a-chip for Integrated Sample Manipulation and Dispensing

Microfluidic based miniature lab-on-a-chip devices integrate different laboratory functionality in microscale. Microarray technology is evolving as a powerful tool for biomedical and pharmaceutical applications to identify gene sequences or to determine gene expression levels. Preparation of samples and spotting the arrays are the two major steps required for making microarrays. The microfluidic components developed in this research would facilitate performing the above-mentioned steps by a single lab-on-a-chip. Three microfluidic modules were developed: a non-contact microdispenser, an interface connecting the microdispenser with planar Electrowetting on Dielectric (EWOD) sample manipulator and a microvalve that controls the flow at the interface. An electrostatically actuated non-contact type drop-on-demand based microdispenser was developed. The dispenser was designed using finite element modeling technique that solved electrostatically actuated dispensing process. Prototypes were fabricated and tested verifying stable droplet dispensing with error in subsequent droplet generation was less than 15% between each droplet. The frequency of stable generation was 20 Hz and the average volume of dispensed droplet was 1 nL. A closed-channel EWOD actuated interface was developed that allowed a series of droplets to merge inside at the interface converting droplet flow to a continuous flow. An innovative design modification allowed series of droplet merging inside closed-channel. The interface allows integration of pressure driven devices such as: pumps, dispensers, and valves with droplet based planar EWOD devices. A novel EWOD based microvalve was developed that utilizes a thermo-responsive polymer to block and unblock a pressurized continuous flow. EWOD actuation was used to control the positioning of the valving polymer at location of interest. The valve also isolated a pressurized flow from an integrated planar EWOD device. Valves with zero leak rates were demonstrated. Such a valve will be useful in controlling microflows in EWOD to pressure driven flows such as dispensers.Ph

Parallel Congruent Electrode Sensor to Detect and Characterize Droplets in a T-Junction Droplet Generator

In this article, we present a simple capacitive droplet sensing method that works with an on-chip droplet generator with real-time sensing capability of droplet composition and size. The sensing system works with the aid of a simple pair of electrodes along the channel wall forming a parallel congruent electrode (PCE)-based capacitor sensor. Using a PCE capacitor, we were able to characterize the droplet based on the material and its size. The droplet generator was classical T-junction-based and was regulated by our latest pneumatic-based control process. We present a numerical model that can simultaneously solve droplet generation and real-time capacitive sensing. The numerical model solves laminar two-phase flow, phase field, and electrostatics multiphysics simultaneously to predict droplet generation and capacitive sensing. We utilized the model to predict the best operating and geometric parameters. Our simulation showed that the electrode width to droplet size ratio of 1:0.95 was the best proportion for sensing droplet movement. This was verified experimentally. The two electrodes in the PCE position outperformed five electrodes in the coplanar interdigital electrode (IE) in the position for the same set of droplet generation. The change in capacitance value was observed using the PCE sensor for the variation in dispersed material and droplet size. The resolution of the sensing was 0.012 pF. The multilayer droplet generation, with simple and simultaneous sensing as well as regulation capability presented in this article, can be useful for the development of controls and sensing for precision droplet generators

Design and development of a MEMS vibrating ring resonator with inner rose petal spring supports

This paper presents a novel MEMS based ring resonator design inspired by the rose petal structure. The proposed design has four petal springs supporting the ring structure surrounded by sense electrodes, with a stem in the middle offering simplicity in fabrication and easy control of movement in the driving and sensing modes. An equation was developed to calculate the stiffness of the support springs, and the stiffness of the proposed design was analyzed and compared to other design parameters. The key geometric elements, such as the petals and the ring dimensions of the proposed design, were selected using finite element modeling techniques to enhance the sensitivity for gyroscope application. The resonance frequencies for different mode shapes were optimized by changing the geometric parameters of the proposed structure. Simulation showed that the proposed design has degenerate mode shapes (with potentially 0 Hz frequency splitting) at resonance frequencies in the range of 25–74 kHz, controlled by increasing the structure’s width from 10 to 30 µm. Scaled-down prototypes of the selected design were fabricated using a customized surface micromachining process. The results of the experiment show that the prototype has a resonance frequency at 64.91 kHz which validates the resonance frequency of the computational model at 64.89 kHz of the same prototype. Good agreement between the simulation and experimental model showed the proof of concept of the design and successful fabrication process

Development of a rapid manufacturable microdroplet generator with pneumatic control

This paper presents a T-junction microdroplet generator equipped with a pneumatic actuation for controlling the droplet size. The multi-layer device is compatible with rapid manufacturing using a desktop-based laser cutter to fabricate the fluidic and pneumatic layers. A T-junction fluidic layer sits at the bottom and the control layer consists of a pneumatic chamber, as well as inlet and outlet channels are placed at the top. Our results with pneumatic control showed that the generated droplet size is inversely proportional to the pressure inside the pneumatic chamber. Pneumatic pressure of up to 0.4 MPa showed a 38% reduction in droplet size compared to without control. The droplet size can additionally be regulated by controlling the relative flow rates of the continuous and dispersed fluid. Pneumatic actuation is advantageous, as it does not require additional fluid usage and the flow rate does not need to be ramped up to decrease the droplet size. The device presented in this paper with pneumatic control and fabrication ease provides an attractive method for microdroplet manipulation

Modulating the Thermechanical Properties and Self-Healing Efficiency of Siloxane-Based Soft Polymers Through Metal-Ligand Coordination

Short oligomeric species end-capped with imine-based ligands can generate intrinsic autonomous self-healable soft polymers upon metal coordination, allowing for the preparation of materials that can be easily fine-tuned in terms of mechanical properties and robustness. To develop a rational understanding of the self-healing mechanism on this system, an investigation of the fine-tuning of the self-healing efficiency by evaluating the metal used to induce crosslinking was performed. Moreover, the counter-ion used in the crosslinking system was also evaluated in order to probe its influence on the final thermomechanical properties. The resulting self-healing polymers were characterized by multiple techniques, including UV-Vis spectroscopy, tensile-strain pull testing, and shear rheology. The metal was shown to have a significant influence on the thermomechanical properties of the system, which can be directly attributed to the coordination geometry (crosslinking density) and bond strength. Moreover, the choice of the counterion used for crosslinking also showed a significant influence on the mechanical properties and self-healing efficiency. These results highlight the versatility of the end-capped polydimethylsiloxane (PDMS)-based system and provide valuable insights for the future development of self-healing polymers that can be produced on a large scale through solution processing, for a wide variety of applications

A comparative analysis of capacitive-based flexible PDMS pressure sensors

This paper focuses on the fabrication, characterization and comparative study of flexible pressure sensors, prepared from structured polydimethylsiloxane (PDMS) as flexible dielectric. In specific, four different patterning methods on PDMS dielectric surface were investigated including inverse mold, replica mold, photolithographic and non-shaped microstructures. The different patterned dielectrics were compared to gain insight onto the effect of flexible microstructure design on pressure sensitivity. A complete material characterization was performed using optical microscopy, scanning electron microscopy and tensile testing to evaluate the physical and electrical properties of the different microstructured PDMS dielectric. Static and dynamic pressure measurements were also performed to determine pressure sensitivities. Our results showed a strong dependence of the pressure sensitivity versus the microstructure patterning method utilized. Dielectric patterned from a simple tape molding procedure showed increased sensitivity at higher-pressure regimes (p \u3e 3 kPa) compared to the photolithographic structured dielectric. The inverse dielectric structures produced a higher sensitivity at pressures less than 3 kPa. This work gives new tools to achieve desired pressure sensitivities in flexible polymer-based sensors, especially for pressures ranging several kPa. The comparative analysis presented in this paper will aid further development of flexible sensors with various tactile sensitivities