In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this problem is to tune the plasmon resonance frequency of the metal nanoparticles to eliminate the need for individually optimized particles. In order to achieve a tunable local dielectric environment, and thus allow for control over the resonance frequency of metal nanoparticles, a new SERS sensor geometry is proposed and a large deflection magnetic actuator is fabricated and tested as a starting point for the design of a small deflection magnetic actuator. Using the newly developed SERS geometry and the optimized fabrication processing techniques, two small deflection magnetic actuator beam structures were designed, fabricated, and tested. These devices utilizes an off-chip electromagnet source able to produce a magnetic force of approximately 14 μN on the on-chip nickel film generating deflections up to 139 nm for the straight beam device and 164 nm for the curved beam device. iii In the process of characterizing the newly developed small deflection magnetic actuator, an integrated magnetic actuator with electrostatic restoration geometry was conceived. This device was designed to meet the specifications of the small deflection magnetic actuator as well as eliminate the need of an off-chip magnetic source and fully integrate the process atop the metal nanoparticle arrays. Using adhesive iron based magnetic strips as the magnetic drive source, circular NiFe beams with 1, 2, 3, and 4 mm diameters were designed and simulated. Calculations predicted maximum achievable actuation of up to 2.5 μm. Processing steps were laid out for a set of integrated devices as a possible predecessor to the newly designed small deflection magnetic actuator.

Modern smartphone technology has created a myriad of opportunities in the field of RF and Microwave. Specifically, Chipless RFID sensor, compact microwave filter, antenna based on a microstrip structure, and many more. In this thesis, innovative ideas for the industrial and biomedical device has been explored. The work presents the reconfigurable filter design, Switch-beam antenna, Microwave interferometer, X-band Rotman Lens antenna, Ultra-wideband antenna based on SIW resonator, L-band Stepped Frequency Continuous Wave antenna, development of a wireless sensor system for environmental monitoring, Indoor Air Quality monitoring, and Wildfire Monitoring based on the modulated scattering technique (MST). The MST sensor probes are based on the scattering properties of small passive antennas and radiate part of the impinging electromagnetic field generated by an interrogating antenna, which also acquires the backscattered signal as information. The MST probes are able to deliver data without a radio frequency front end. They use a simple circuit that alternatively terminates the antenna probe on suitable loads to generate a low modulation signal on the backscattered electromagnetic wave. The antenna presented in this work has been designed in ADS Software by Keysight Technologies. The designed antenna has been assessed numerically and experimentally. The experimental measurement data demonstrate the effectiveness of the individual system. Simultaneously, the MST sensor system has been proposed to obtain the best performance in communication range, load efficiency, and power harvesting. The MST sensor has been fabricated and assessed in practical scenarios. The proposed prototype, able to provide a communication range of about 15 m, serves as a proof-of-concept. The acquired measurements of MST demonstrate the accuracy of the data without radio frequency front end or bulky wired connection with the same efficiency of standard wireless sensors such as radio frequency identifier (RFID) or wireless sensor networks (WSN).

No description available.

Cancer progression and physiological changes within the cells are accompanied by alterations in the biophysical properties. Therefore, the cell biophysical properties can serve as promising markers for cancer detection and physiological activities. To aid in the investigation of the biophysical markers of cells, a microfluidic chip has been developed which consists of a constriction channel and embedded microelectrodes. Single-cell impedance magnitudes at four frequencies and entry and travel times are measured simultaneously during their transit through the constriction channel. This microchip provides a high-throughput, label-free, automated assay to define biophysical signatures of malignant cells and monitor the therapeutic efficacy of drugs. Here, we monitored the dynamic cellular biophysical markers in response to sphingosine kinase inhibitors (SphKIs), and compared the effectiveness of drug delivery using Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with SphKIs versus conventional delivery. Cells treated with SphKIs showed significantly higher impedance magnitudes at all four frequencies. The bioelectrical parameters extracted using a model also revealed that the highly aggressive breast cells treated with SphKIs shifted electrically towards that of a less malignant phenotype; SphKI-treated cells exhibited an increase in cell-channel interface resistance and a significant decrease in specific membrane capacitance. Furthermore, SphKI-treated cells became slightly more deformable as measured by a decrease in their channel entry and travel times. We observed no significant difference in the bioelectrical changes produced by SphKI delivered conventionally or with NPs. However, NPs-packaged delivery of SphKI decreased the cell deformability. In summary, the results showed that while the bioelectrical properties of the cells were dominantly affected by SphKIs, the biomechanical properties were mainly changed by the NPs. / Master of Science

This dissertation presents the investigation of three thin film materials used in microelectromechanical systems (MEMS): alumina, silicon, and nickel. For this purpose, novel experimental techniques to test thin films under MEMS-relevant loading conditions were developed in order to study environmental effects and the underlying fatigue mechanisms of amorphous alumina ultra-thin coatings, mono-crystalline brittle silicon thin films, and poly-crystalline ductile nickel thin films. Knowledge of these mechanisms is necessary to improve the reliability of MEMS, especially of those devices operating in harsh environments. MEMS resonators were used to investigate both the fatigue and time-dependent behavior of alumina, silicon, and nickel. While micro-resonators were used in prior studies to research the fatigue properties of mono- and polycrystalline silicon, this work is the first in (1) using them to investigate fatigue properties of ultra-thin coatings and metallic films and in (2) using micro-resonators to investigate the time-dependent fatigue behavior of silicon films. For fatigue testing, the micro-resonators were subjected to fully-reversed loading at resonance (≈40 kHz for alumina-coated silicon, ≈8 kHz for nickel). Experiments were conducted in air at 30 °C, 50% relative humidity (RH) or 80 °C, 90% RH and testing was carried out over a broad range of applied stresses. The resonance frequency evolution proved to be a metric for the accumulated damage, which could be further quantified using finite element analysis. In addition, scanning and transmission electron microscopy were used to examine the extent of fatigue damage. For testing under static loads, the resonators were subjected to external loading using a micromanipulator and probe-tip. Experiments with atomic-layer-deposited alumina investigated the cohesive and interfacial fatigue properties of alumina coatings of four different thicknesses, ranging from nominally 4.2 nm to 50.0 nm on silicon micro-resonators. Fatigue loading led to both cohesive and interfacial damage, while static loading did not result in any damage. Both the cohesive and interfacial fatigue crack growth rates are approximately one order of magnitude higher at 80 °C, 90% RH than at 30 °C, 50% RH and seem to increase with increasing strain energy release rate. A combination of compressive loading and the silicon sidewall's surface roughness is believed to cause the observed fatigue behavior. Experiments with 10-micrometer-thick deep reactive ion etched silicon micro-resonators investigated two aspects: whether surface oxidation is the critical parameter in silicon thin film fatigue and time-dependent failure in silicon as a potential underlying cause of resonator failures in the low cycle fatigue (LCF, <17 cycles, corresponding to ≈5 min) regime. To confirm whether surface oxidation is the critical parameter in silicon thin film fatigue, the influence of oxygen diffusion barrier alumina coatings on the fatigue behavior was investigated. The coatings led to an increase in fatigue life by at least two orders of magnitude compared to uncoated devices in the harsh environment, which not only confirms reaction layer fatigue (RLF) as governing fatigue mechanism in silicon thin films, but also constitutes a practical solution to significantly increase fatigue lifetimes. Previous LCF data were inconsistent with the RLF model, given that thick surface oxidation is unrealistic for tests lasting only few minutes. Accordingly, time-dependent failure in silicon was investigated as underlying cause and the observation of resonator failures under static loading indeed suggest that time-dependent crack growth may be responsible for LCF failures. Experiments with metallic micro-resonators investigated the fatigue crack initiation in 20-micrometer-thick electro-deposited nickel under MEMS-relevant conditions, such as extreme stress gradients resulting in non-propagating cracks, fully-reversed loading (over a large range of stress amplitudes), exposure to mild and harsh environments, and accumulation of billions of cycles. Under these circumstances, extrusions form locally at the notch root (within few million cycles at high stress amplitudes). Very thick local oxides (only at the location of the extrusions) of up to 1100 nm were observed in the harsh environment, with thinner oxides (up to 700 nm) in the mild environment. Micro-cracks form in the oxide but do not propagate given the extreme stress gradients. Finite element analysis confirmed that oxidation and micro-cracking lead to changes in the resonance frequency, which are consistent with the experimental results. Accumulation of cyclic plasticity appears to also lead to a decrease in resonance frequency which scales with applied strain.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The valveless micropump holds great potential for the biomedical community in applications such as drug delivery systems, blood glucose monitoring and many others. It is also a critical component in many a lab-on-a-chip device, which in turn promises to improve our treatment and diagnosis capabilities for diseases such as diabetes, tuberculosis, and HIV/AIDS. The valveless micropump has attracted attention from researchers on the grounds of its simple design, easy manufacturability and sensitive fluid handling characteristics, which are all important in biomedical applications. The pump consists of a pump chamber with a diffuser and nozzle on opposing sides of the pump chamber. The flow into the diffuser and nozzle is induced by an oscillating piezoelectric disc located on top of the pump chamber. The nozzle and diffuser rectify the flow in one direction, due to different pressure loss coefficients. The design process however is complex. In this study, we investigate the characteristics of a diffuser / nozzle based micropump using detailed computational fluid dynamic (CFD) analyses. Significant parameters are derived using the Buckingham-Pi theorem. In part based on this, the respective shapes of the diffuser and of the nozzle of the micropump are selected for numerical investigation. Hence the influence of the selected parameters on the flow rate of the micropump is studied using three-dimensional transient CFD analyses. Velocity profiles from the CFD simulations are also compared to the Jeffery-Hamel solution for flow in a wedge shaped channel. Significant similarities exist between the data and the predicted Jeffery-Hamel velocity profiles near the exit of the diffuser. Three different diffuser geometries were simulated at three frequencies. The flow rate and direction of flow are shown to be highly sensitive to inlet and outlet diffuser shapes, with the absolute flow rate varying by as much as 200% for the geometrical perturbations studied. Entrance losses at both the diffuser inlet and nozzle inlet appear to dominate the flow resistance at extremely laminar flow conditions with the average Reynolds number of Reave ≈ 500. / AFRIKAANSE OPSOMMING: Die kleplosemikropomp hou groot potensiaal in vir die biomediese gemeenskap in toepassings soos medisyne dosering sisteme, bloed glukose monitering en baie ander. Dit is ook ’n kritiese komponent in “lab-on-chip” sisteme, wat beloof om die behandeling en diagnose van siektes soos suikersiekte, tuberkulose enMIV/VIGS te verbeter. Die kleplose mikropomp het tot dusver die aandag van navorsers geniet as gevolg van sy eenvoudige ontwerp, maklike vervaardiging en sensitiewe vloeistof hantering. Hierdie kenmerke is krities inmenige biomediese toepassings. Die pomp bestaan uit ’n pompkamer met ’n diffusor en ’n mondstuk aan teenoorstaande kante van die pompkamer. Vloei in die diffusor en mondstuk in word geinduseer deur ’n ossillerende piëso-elektiese skyf wat bo-op die pompkamer geleë is. Weens verskillende druk verlies koëffisinëte van die diffusor en diemondstuk word die vloei in een rigting gerig. Die ontwerp-proses is egter kompleks. In hierdie studie word die eienskappe van die diffusor /mondstuk ondersoek deur gebruik temaak van gedetailleerde numeriese vloei-dinamiese analises. Belangrike parameters word afgelei deur gebruik te maak van die Buckingham-Pi teorema. Gedeeltelik gebaseer hierop word die onderskeidelike vorms van die diffusor en die mondstuk van die mikropomp geselekteer vir numeriese ondersoek. Gevlolglik word die invloed van die geselekteerde parameters op die vloei tempo van diemikropomp ondersoek deur gebruik temaak van drie-dimensionele tyd afhanklike numeriese vloei-dinamiese analises. Snelheids profiele van hierdie simulasiesword vergelykmet die Jeffrey-Hamel oplossing vir die vloei in ’n wigvormige kanaal. Daar is oorwegende ooreenkomstighede tussen hierdie data en die voorspelde Jeffrey-Hamel snelheids profiele veral by die uitgang van die diffusor. Drie verskillende diffusor vorms is by drie frekwensies gesimuleer. Daar is bewys dat die vloei tempo en vloeirigting baie sensitief is vir inlaat- en uitlaat diffusor vorms en dat die absolute vloei tempo kan varieermet soveel as 200%vir die geometriese versteuringswat ondersoek is. Inlaat verliese by beide die diffusor inlaat en die mondstuk inlaat, blyk om die vloei weerstand te domineer waar die vloei uiters laminêr ismet ’n gemiddelde Reynolds getal van Regem ≈ 500

Microelectromechanical systems (MEMS) devices have been increasing in popularity for radio frequency (RF) and microwave communication systems due to the ability of MEMS devices to improve the performance of these circuits and systems. This interdisciplinary field combines the aspects of lithographic fabrication, mechanics, materials science, and RF/microwave circuit technology to produce moving structures with feature dimensions on the micron scale (micro-structures). MEMS technology has been used to improve switches, varactors, and inductors to name a few specific examples. Most MEMS devices have been fabricated using planar micro fabrication techniques that are similar to current integrated circuit (IC) fabrication techniques. These techniques limit the thickness of individual layers to a few microns, and restrict the structures to have planar and not vertical features. One micro fabrication technology that has not seen much application to microwave MEMS devices is LIGA, a German acronym for X-ray lithography, electroforming, and moulding. LIGA uses X-ray lithography to produce very tall structures (hundreds of microns) with excellent structural quality, and with lateral feature sizes smaller than a micron. These unique properties have led to an increased interest in LIGA for the development of high performance microwave devices, particularly as operating frequencies increase and physical device size decreases. Existing work using LIGA for microwave devices has concentrated on statically operating structures such as transmission lines, filters, couplers, and antennas. This research uses these unique fabrication capabilities to develop dynamically operating microwave devices with high frequency performance. This thesis documents the design, fabrication and testing of LIGA-MEMS variable capacitors that exploit the vertical dimension. Also included are methods to improve both the reliable fabrication and operation of these devices as well as material property characterization. Variable capacitors can be found in systems such as voltage-controlled oscillators, filters, impedance matching networks and phase shifters. Important figures-of-merit for these devices include the quality factor (Q), tuning range and tuning voltage. Two different types of variable capacitors are presented, a pull-away design and a design based on the principle of leveraged bending. The pull-away style variable capacitors were found to have high Q-factors, especially the devices fabricated using a thick gold device layer. As an example, the small gold half capacitance electrode design features a Q-factor of 95 at an operating frequency of 5.6 GHz and a tuning ratio of 1.36:1 with a tuning voltage range of 0 to 7.8 V. The design based on leveraged bending significantly improves the tuning ratio to a value of 1.9:1 while still maintaining a high Q-factor similar to those found in the pull-away style designs. A further increase in tuning ratio to a value of approximately 2.7:1 would be possible, based on simulated results, by simply changing the angle of the capacitance electrode in the layout. To improve device performance and fabrication reliability, modifications were made to both the fabrication process and the device layout. In the fabrication process the exposure step, electroplating step, and the etching process were modified to improve the quality of the resulting devices. In the layout, anti-stiction measures were introduced that reduce the contact area during collapse. To improve device characterization as well as the feedback link between simulation and fabrication, a set of test structures called VM-TEST was developed to accurately determine the important mechanical material properties of thick electroplated layers. These structures utilize the measurement of the pull-in voltage in cantilever and fixed-fixed beams, along with measured structure dimensions, to accurately extract the mechanical properties. Both nickel and gold test structures were analyzed with extracted Young’s modulus values of 186.2 and 60.8 GPa respectively. Also presented is a study of the gap shape in cantilever and fixed-fixed beams that significantly reduces the pull-in voltage while still maintaining a required maximum actuator displacement. It was shown that in the case of cantilever beam actuators, an approximately 40% reduction in pull-in voltage is possible, and in the case of fixed-fixed beam actuators, an approximately 30% reduction is possible by simply varying the shape of the gap between the beam and actuator electrode. These results can be used to significantly reduce the pull-in voltage of future designs. These promising results show that the LIGA fabrication process is capable of producing high performance dynamically operating RF MEMS devices, by exploiting the vertical dimension, not typically performed in most existing RF MEMS designs.

Approved for public release; distribution in unlimited. / MEMS technology is rapidly taking an important role in today's and future military systems. MEMS are able to lower the device size from millimeter to micrometer and maintain and sometimes surpass the performance of conventional devices. This thesis encompasses the knowledge acquired throughout the MEMS courses to design a two-axis capacitive accelerometer. The required acceleration and operating temperature range were Š50g in each axis and -40ʻC to +80 ʻC, respectively. The accelerometer was also needed to survive within a dynamic shocking environment with accelerations of up to 225g. The parameters of the accelerometer to achieve above specifications were calculated using lumped element approximation and the results were used for initial layout of it. A finite element analysis code (ANSYS) was used to perform simulations of the accelerometer under various operating conditions and to determine the optimum configuration. The simulated results were found to be within about 5% of the calculations indicating the validity of lumped element approach. The response of the designed accelerometer was 7 mV/g and with sensitivity of 1.3g at 3dB. It was also found that the accelerometer was stable in the desired range of operation including under the shock. Two axes sensing can be achieved using two identical accelerometers having their sensing axes perpendicular to each other. / Major, Taiwan Army

Um fator importante para o desenvolvimento de projetos de microssistemas é o conhecimento de propriedades termomecânicas dos materiais e a compreensão dos mecanismos de falhas. Este trabalho estuda o comportamento mecânico de microvigas atuadas termicamente e propõem um método para ser utilizado na caracterização de propriedades termomecânicas de filmes finos. Fabricou-se vigas de Oxinitreto de Silício em que se aplicou a microscopia Nomarski para observar a deformação e a ocorrência do fenômeno de flambagem. / An important factor to develop microsystems is knowledge of materials properties and failure mechanisms. This research studies the thermal actuated microbeam mechanical behavior and propose a method in order to characterize thermomechanical properties of thin films. Silicon Oxynitride microbeams are fabricated and Nomarski microscopy was applied to observe strain and buckling phenomenon ocurrence.

"Health monitoring of structures by experimental modal analysis is typically performed with piezoelectric based transducers. These transducers are usually heavy, large in size, and require high power to operate, all of which reduce their versatility and applicability to small components and structures. The advanced developments of microfabrication and microelectromechanical systems (MEMS) have lead to progressive designs of small footprint, low dynamic mass and actuation power, and high-resolution inertial sensors. Because of their small dimensions and masses, MEMS inertial sensors could potentially replace the piezoelectric transducers for experimental modal analysis of small components and structures. To transfer data from MEMS inertial sensors to signal analyzers, traditional wiring methods may be utilized. Such methods provide reliable data transfer and are simple to integrate. However, in order to study complex structures, multiple inertial sensors, attached to different locations on a structure, are required. In such cases, using wires increases complexity and eliminates possibility of achieving long distance monitoring. Therefore, there is a need to implement wireless communications capabilities to MEMS sensors. In this thesis, two different wireless communication systems have been developed to achieve wireless health monitoring of structures using MEMS inertial sensors. One of the systems is designed to transmit analog signals, while the other transmits digital signals. The analog wireless system is characterized by a linear frequency response function in the range of 400 Hz to 16 kHz, which covers the frequency bandwidth of the MEMS inertial sensors. This system is used to perform modal analysis of a test structure by applying multiple sensors to the structure. To verify the results obtained with MEMS inertial sensors, noninvasive, laser optoelectronic holography (OEH) methodology is utilized to determine modal characteristics of the structure. The structure is also modeled with analytical and computational methods for correlation of and verification with the experimental measurements. Results indicate that attachment of MEMS inertial sensors, in spite of their small mass, has measurable effects on the modal characteristics of the structure being considered, verifying their applicability in health monitoring of structures. The digital wireless system is used to perform high resolution tilt and rotation measurements of an object subjected to angular and linear accelerations. Since the system has been developed based on a microcontroller, programs have been developed to interface the output signals of the sensors to the microcontroller and RF components. The system is calibrated using the actual driving electronics of the MEMS sensors, and it has achieved an angular resolution of 1.8 mrad. The results show viability of the wireless MEMS inertial sensors in applications requiring accurate tilt and rotation measurements. Additional results presented included application of a MEMS gyroscope and microcontroller to perform angular rate measurements. Since the MEMS gyroscope only generates analog output signals, an analog to digital conversion circuit was developed. Also, a program has been developed to perform analog to digital conversion with two decimal places of accuracy. The experimental results demonstrate feasibility of using the microcontroller and the gyroscope to perform wireless angular rate measurements."