184 research outputs found

    Silicon-Integrated Two-Dimensional Phononic Band Gap Quasi-Crystal Architecture

    Get PDF
    The development and fabrication of silicon-based phononic band gap crystals has been gaining interest since phononic band gap crystals have implications in fundamental science and display the potential for application in engineering by providing a relatively new platform for the realization of sensors and signal processing elements. The seminal study of phononic band gap phenomenon for classical elastic wave localization in structures with periodicity in two- or three-physical dimensions occurred in the early 1990’s. Micro-integration of silicon devices that leverage this phenomenon followed from the mid-2000’s until the present. The reported micro-integration relies on exotic piezoelectric transduction, phononic band gap crystals that are etched into semi-infinite or finite-thickness slabs which support surface or slab waves, phononic band gap crystals of numerous lattice constants in dimension and phononic band gap crystal truncation by homogeneous mediums or piezoelectric transducers. The thesis reports, to the best of the author's knowledge, for the first time, the theory, design methodology and experiment of an electrostatically actuated silicon-plate phononic band gap quasi-crystal architecture, which may serve as a platform for the development of a new generation of silicon-integrated sensors, signal processing elements and improved mechanical systems. Electrostatic actuation mitigates the utilization of piezoelectric transducers and provides action at a distance type forces so that the phononic band gap quasi-crystal edges may be free standing for potentially reduced anchor and substrate mode loss and improved energy confinement compared with traditional surface and slab wave phononic band gap crystals. The proposed phononic band gap quasi-crystal architecture is physically scaled for fabrication as MEMS in a silicon-on-insulator process. Reasonable experimental verification of the model of the electrostatically actuated phononic band gap quasi-crystal architecture is obtained through extensive dynamic harmonic analysis and mode shape topography measurements utilizing optical non-destructive laser-Doppler velocimetry. We have utilized our devices to obtain fundamental information regarding novel transduction mechanisms and behavioral characteristics of the phononic band gap quasi-crystal architecture. Applicability of the phononic band gap quasi-crystal architecture to physical temperature sensors is demonstrated experimentally. Vibration stabilized resonators are demonstrated numerically

    Micro-Resonators: The Quest for Superior Performance

    Get PDF
    Microelectromechanical resonators are no longer solely a subject of research in university and government labs; they have found a variety of applications at industrial scale, where their market is predicted to grow steadily. Nevertheless, many barriers to enhance their performance and further spread their application remain to be overcome. In this Special Issue, we will focus our attention to some of the persistent challenges of micro-/nano-resonators such as nonlinearity, temperature stability, acceleration sensitivity, limits of quality factor, and failure modes that require a more in-depth understanding of the physics of vibration at small scale. The goal is to seek innovative solutions that take advantage of unique material properties and original designs to push the performance of micro-resonators beyond what is conventionally achievable. Contributions from academia discussing less-known characteristics of micro-resonators and from industry depicting the challenges of large-scale implementation of resonators are encouraged with the hopes of further stimulating the growth of this field, which is rich with fascinating physics and challenging problems

    Building a novel nanofabrication system using MEMS

    Full text link
    Micro-electromechanical systems (MEMS) are electrically controlled micro-machines which have been widely used in both industrial applications and scientific research. This technology allows us to use macro-machines to build micro-machines (MEMS) and then use micro-machines to fabricate even smaller structures, namely nano-structures. In this thesis, the concept of Fab on a Chip will be discussed where we construct a palette of MEMS-based micron scale tools including lithography tools, novel atomic deposition sources, atomic mass sensors, thermometers, heaters, shutters and interconnect technologies that allow us to precisely fabricate nanoscale structures and conduct in-situ measurements using these micron scale devices. Such MEMS devices form a novel microscopic nanofabrication system that can be integrated into a single silicon chip. Due to the small dimension of MEMS, fabrication specifications including heat generation, patterning resolution and film deposition precision outperform traditional fabrication in many ways. It will be shown that one gains many advantages by doing nano-lithography and physical vapor deposition at the micron scale. As an application, I will showcase the power of the technique by discussing how we use Fab on a Chip to conduct quench condensation of superconducting Pb thin films where we are able to gently place atoms upon a surface, creating a uniform, disordered amorphous film and precisely tune the superconducting properties. This shows how the new set of techniques for nanofabrication will open up an unexplored regime for the study of the physics of devices and structures with small numbers of atoms

    Millimeter-Scale Encapsulation of Wireless Resonators for Environmental and Biomedical Sensing Applications

    Full text link
    Wireless magnetoelastic resonators are useful for remote mapping and sensing in environments that are harsh or otherwise difficult to access. Compared to other wireless resonators, magnetoelastic devices are attractive because of their inherently wireless nature, and their ability to operate passively without a power source, integrated circuitry, or antenna. An open challenge for using miniaturized magnetoelastic resonators is application-tailored encapsulation and packaging. General packaging considerations for magnetoelastic resonators include not only the mechanical design but also electromagnetic transparency, adaptability of form factor with appropriate feature size, and chemical inertness and/or biocompatibility. In this thesis, the packaging of magnetoelastic resonators is investigated in two contexts: environmental sensing and biomedical sensing. The first context is for tagging and mapping applications in a high temperature (≥ 150°C), high pressure (≥ 10 MPa), corrosive environment, such as a hydraulic fracture branching from a wellbore. This work utilizes for the first time a micro molding process to thermoform liquid crystal polymer (LCP) packages for protecting magnetoelastic resonators. The package is < 10 mm3 and includes micron-scale features to support the resonator and allow it to vibrate with low loss. It has an average shear strength of 60 N, and can endure pressure up to 2000 psi (≈13.8 MPa). The second context is for implantable magnetoelastic resonators, which are used for sensing biological parameters. These packages must: protect the sensors during deployment through an endoscope, be biocompatible and chemically inert, be able to pass through a complex delivery path, and fit within a limited size. Protecting the resonator during delivery while still allowing interaction with biological fluids is achieved with polymeric packages incorporating features such as a perforated housing and tapered and smoothed edges. This approach also includes features to aid in assembling with plastic stents via polyethylene tethers. The packaged resonator must pass through a complex delivery path without damage due to bending, so the compromise between two architectures – one mechanically flexible (Type F) and one mechanically stiff (Type S) – is evaluated. The primary advantage of the Type F package is the flexibility of the package during the delivery process while that of the Type S package is to maintain a strong signal even when the stent is in a curved bile duct. The length, width, and maximum thickness of the Type F package are 26.40 mm, 2.30 mm and 0.53 mm, respectively. The Type S package has an outer diameter of 2.54 mm, a length of 15 mm, and a maximum thickness of 0.74 mm. The two package types are tested in benchtop flexibility tests, and in vivo and in situ in porcine specimens. The animal tests demonstrate partial functionality of both types of packages, while also indicating that smaller and more elastic package designs are needed. Remaining in the implantable sensor context, an improved and miniaturized resonator design is explored. Miniaturizing the resonator accordingly allows miniaturization of the packaging, reducing the impact on the overall functionality of the medical device. The fabricated sensor is 8.25 mm long, 1 mm wide with the largest thickness of 218 μm. The resonant frequency of the resonator is around 173 kHz which is similar to that of a 12.5 mm long ribbon sensor. This resonator design is self-biased, simplifying the packaging and assembly compared to previous designs.PHDElectrical & Computer Eng PhDUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146089/1/jqjiang_1.pd

    Frequency Stability in Thin-film Piezoelectric-on-substrate Oscillators

    Get PDF
    For many years, crystal oscillators have been used as the de facto frequency reference in almost all electronic platforms because they offer excellent stability and superior phase noise. This is mainly due to the high quality factor (Q) and exceptional temperature stability of quartz crystals. However, the size of quartz resonators is relatively large, and they cannot be readily integrated with microelectronics. This ultimately impedes the complete integration of the high-performance oscillators with the electronics. Achieving such integration will enable frequency control devices with a smaller form factor, lower cost, greater flexibility, and potentially higher reliability. Microelectromechanical systems (MEMS) resonator technology is gradually gaining popularity as a solution for the integration barrier and high-performance micro-machined oscillators have been presented by researchers and companies recently. However, one of the most important drawbacks of MEMS resonators has been their relatively large and linear temperature coefficient of frequency (TCF) (e.g., around -30 ppm/C for Si-based). The subject of this presentation is on the frequency stability in thin-film piezoelectric-on-substrate oscillators (TPoS). In this regard, jitter and temperature dependency of the oscillation frequency are studied. The dependency of jitter of TPoS on the resonator characteristics (i.e. quality factor and motional impedance) is studied where the results provide experimental validation for the suppression of overall oscillator circuit noise through the operation of the resonator beyond the bifurcation.A novel temperature compensation technique for silicon-based lateral-extensional MEMS oscillators is introduced, which is based on the properly orienting an extensional-mode resonator on a highly doped n-type silicon substrate. The existence of a local zero temperature coefficient of frequency (i.e., turnover point) in extensional-mode silicon microresonators, fabricated on highly n-type-doped substrates and aligned to the [100] crystalline orientation is demonstrated. It is shown that the turnover point in TPoS resonators is a function of doping concentration and orientation. Moreover, the turnover point can be adjusted by changing the thickness ratio of Si and the piezoelectric film (e.g., AlN) in the resonant structure. MEMS oscillators with controlled temperature coefficient of frequency (TCF), assembled through mixing the frequencies of two oscillators that are made of silicon micro-resonators with known and dissimilar TCF, are also introduced. Based on this method, a TPoS MEMS oscillator is assembled in which the first-order TCF is virtually cancelled resulting in a parabolic TCF curve (second-order TCF).The frequency tuning in TPoS resonators is also reported which results show a great potential application in temperature compensated oscillators. Tuning is demonstrated through varying the termination load connected to an isolated tuning port. The dependency of frequency tuning on the design features of the resonator is studied as well.Electrical Engineerin

    Engineering planetary lasers for interstellar communication

    Get PDF
    Transmitting large amounts of data efficiently among neighboring stars will vitally support any eventual contact with extrasolar intelligence, whether alien or human. Laser carriers are particularly suitable for high-quality, targeted links. Space laser transmitter systems designed by this work, based on both demonstrated and imminent advanced space technology, could achieve reliable data transfer rates as high as 1 kb/s to matched receivers as far away as 25 pc, a distance including over 700 approximately solar-type stars. The centerpiece of this demonstration study is a fleet of automated spacecraft incorporating adaptive neural-net optical processing active structures, nuclear electric power plants, annular momentum control devices, and ion propulsion. Together the craft sustain, condition, modulate, and direct to stellar targets an infrared laser beam extracted from the natural mesospheric, solar-pumped, stimulated CO2 emission recently discovered at Venus. For a culture already supported by mature interplanetary industry, the cost of building planetary or high-power space laser systems for interstellar communication would be marginal, making such projects relevant for the next human century. Links using high-power lasers might support data transfer rates as high as optical frequencies could ever allow. A nanotechnological society such as we might become would inevitably use 10 to the 20th power b/yr transmission to promote its own evolutionary expansion out of the galaxy

    Development of a 1D phased ultrasonic array for intravascular sonoporation

    Get PDF
    Error on title page – year of award is 2021.Sonoporation represents a promising approach to increase targeted drug delivery efficiency by facilitating transport of therapeutic agents to the target tissue with the use of ultrasound. However, most of the current research in sonoporation is performed with external ultrasonic transducers, which hinders the applicability of the therapeutic procedure for treatment of conditions situated deeper into the patient’s body, such as liver or intestinal tumours. This Thesis presents the development process of a miniature-sized 1-3 connectivity piezocomposite 1D phased array for intracorporeal sonoporation. The device was to be incorporated into a capsule or catheter and hence the primary design constraint was the reduced size of the piezoelectric element, which was limited to 2.5 mm in width and 12 mm in length. To meet the needs of the intended application, resonance frequencies of 1.5 MHz and 3.0 MHz were considered. A simulation framework was developed for optimization of the miniature array in relation to the peak negative pressure attained at the focus to mitigate the low power output associated with the limited device dimensions. This was implemented through a multiparametric sweep of the 1-3 piezocomposite geometry-related parameters. Devices made with PZT-5H and PMN-29%PT were evaluated. The optimization algorithm was used to determine specifications for phased array designs based on the two materials and the two resonance frequencies. The 1.5 MHz devices comprised 24 elements and the 3.0 MHz ones had 32 elements. The piezocomposites were manufactured using the dice and fill technique and electroded using a novel method of electrode deposition employing spin coating of Ag ink. Subsequently, the prototype devices were driven with a commercial array controller and characterized with a calibrated needle hydrophone in a scanning tank. Two simulation profiles based on finite element analysis and time extrapolation were developed to model the acoustic beams from the arrays, which were compared and calibrated with experimental data for focal distances between 5 mm and 10 mm and beam steering angles from 0° to 40°. The results showed that modelling could be employed reliably for therapeutic planning. Both the 1.5 MHz and the 3.0 MHz, PZT-5H arrays were tested in vitro and shown to induce and control sonoporation of a human epithelial colorectal adenocarcinoma cell layer. Finally, a 24 element, 1.5 MHz, PZT-5H array was implemented in a 40 mm long by 11 mm diameter tethered, biocompatible capsule intended for in vivo operation. The device was characterized in the scanning tank for steering angles in the range 0° to 56° and focal distances between 4.0 mm and 5.7 mm, and the measured beam profiles were correlated with the simulation framework. The capsule will be tested in future ex-vivo and in-vivo experiments on insulin absorption through porcine small bowel by means of sonoporation.Sonoporation represents a promising approach to increase targeted drug delivery efficiency by facilitating transport of therapeutic agents to the target tissue with the use of ultrasound. However, most of the current research in sonoporation is performed with external ultrasonic transducers, which hinders the applicability of the therapeutic procedure for treatment of conditions situated deeper into the patient’s body, such as liver or intestinal tumours. This Thesis presents the development process of a miniature-sized 1-3 connectivity piezocomposite 1D phased array for intracorporeal sonoporation. The device was to be incorporated into a capsule or catheter and hence the primary design constraint was the reduced size of the piezoelectric element, which was limited to 2.5 mm in width and 12 mm in length. To meet the needs of the intended application, resonance frequencies of 1.5 MHz and 3.0 MHz were considered. A simulation framework was developed for optimization of the miniature array in relation to the peak negative pressure attained at the focus to mitigate the low power output associated with the limited device dimensions. This was implemented through a multiparametric sweep of the 1-3 piezocomposite geometry-related parameters. Devices made with PZT-5H and PMN-29%PT were evaluated. The optimization algorithm was used to determine specifications for phased array designs based on the two materials and the two resonance frequencies. The 1.5 MHz devices comprised 24 elements and the 3.0 MHz ones had 32 elements. The piezocomposites were manufactured using the dice and fill technique and electroded using a novel method of electrode deposition employing spin coating of Ag ink. Subsequently, the prototype devices were driven with a commercial array controller and characterized with a calibrated needle hydrophone in a scanning tank. Two simulation profiles based on finite element analysis and time extrapolation were developed to model the acoustic beams from the arrays, which were compared and calibrated with experimental data for focal distances between 5 mm and 10 mm and beam steering angles from 0° to 40°. The results showed that modelling could be employed reliably for therapeutic planning. Both the 1.5 MHz and the 3.0 MHz, PZT-5H arrays were tested in vitro and shown to induce and control sonoporation of a human epithelial colorectal adenocarcinoma cell layer. Finally, a 24 element, 1.5 MHz, PZT-5H array was implemented in a 40 mm long by 11 mm diameter tethered, biocompatible capsule intended for in vivo operation. The device was characterized in the scanning tank for steering angles in the range 0° to 56° and focal distances between 4.0 mm and 5.7 mm, and the measured beam profiles were correlated with the simulation framework. The capsule will be tested in future ex-vivo and in-vivo experiments on insulin absorption through porcine small bowel by means of sonoporation

    Nonlinear springs with applications to flow regulation valves and mechanisms

    Get PDF
    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 193-195).This thesis focuses on the application of nonlinear springs for fluid flow control valves where geometric constraints, or fabrication technologies, limit the use of available solutions. Types of existing nonlinear springs are discussed and categorized as either, single element springs or springs relying on external elements to provide nonlinear characteristics. This work discusses the design principles of, both, hardening and softening nonlinear springs and the development of a nonlinear spring system using a contact surface to increase or decrease stiffness. This work has been motivated by the development of a new automotive positive crankcase ventilation (PCV) valve that meets the flow requirements of the current production valve, yet resist stiction commonly associated with the freezing of the valve's internal components. The valve regulates the PCV system, which ventilates corrosive gases from the crankcase. Using the nonlinear spring design principles developed here, a valve has been designed that is estimated to cost 90% less than the current production valve, addresses the issue of freezing, reduces oil consumption by 54%, is less prone to hysteresis and eliminates flutter instabilities that cause the valve to violate flow specification. This thesis concludes with a discussion of the potential for this type of nonlinear spring in medical devices, toys, microsystems, mechanical couplings and fixturing.by David C. Freeman, Jr.Ph.D

    BULK-PIEZOELECTRIC TRANSDUCTION OF MICROSYSTEMS WITH APPLICATIONS TO BATCH-ASSEMBLY OF MICROMIRRORS, CAPACITIVE SENSING, AND SOLAR ENERGY CONCENTRATION

    Full text link
    Electromechanical modeling, actuation, sensing and fabrication aspects of bulkpiezoelectric ceramic integration for microsystems are investigated in this thesis. A small-signal model that describes the energy exchange between surface micromachined beams and bulk-lead zirconium titanate (PZT) actuators attached to the silicon substrate is presented. The model includes detection of acoustic waves launched from electrostatically actuated structures on the surface of the die, as well as their actuation by bulk waves generated by piezoelectric ceramics. The interaction is modeled via an empirical equivalent circuit, which is substantiated by experiments designed to extract the model parameters. As a die level application of bulk-PZT, an Ultrasound Enhanced Electrostatic Batch Assembly (U2EBA) method for realization of 3-D microsystems is demonstrated. U2EBA involves placing the die in an external DC electric field perpendicular to the substrate and actuating the die with an off-chip, bulk-piezoelectric ceramic. Yield rates reaching up to 100% are reported from 8×8 arrays of hinged mirrors with dimensions of 180 × 100 micrometre-squared. U2EBA is later improved to provide temporary latching at intermediate angles between fully horizontal and vertical states, by using novel latching structures. It is shown that the micromirrors can be trapped and freed from different rotation angles such that zero static power is needed to maintain an angular position. The zero-idle-power positioning of large arrays of small mirrors is later investigated for energy redirection and focusing. All-angle LAtchable Reflector (ALAR) concept is introduced, and its application to Concentrated Solar Power (CSP) systems is discussed. The main premise of ALAR technology is to replace bulky and large arrays of mirrors conventionally used in CSP technologies with zeroidle- power, semi-permanently latched, low-profile, high-fill factor, micrometer to centimeter scale mirror arrays. A wirelessly controlled prototype that can move a 2-D array of mirrors, each having a side length of less than 5 cm, in two degrees of freedom to track the brightest spot in the ambient is demonstrated. Capacitive sensing using bulk-piezoelectric crystals is investigated, and a Time- Multiplexed Crystal based Capacitive Sensing (TM-XCS) method is proposed to provide nonlinearity compensation and self-temperature sensing for oscillator based capacitive sensors. The analytical derivation of the algorithm and experimental evidence regarding the validity of some of the relations used in the derivation are presented. This thesis also presents results on microfluidic particle transport as another application of bulk-PZT in microsystems. Experiments and work regarding actuation of micro-scale, fluorescent beads on silicon nitride membranes are described

    Probing multivalent particle–surface interactions using a quartz crystal resonator

    Get PDF
    The rise in market-approved cellular therapies demands for advancements in process analytical technology (PAT) capable of fulfilling the requirements of this new industry. Unlike conventional biopharmaceuticals, cell-based therapies (CBT) are complex “live” products, with a high degree of inherent biological variability. This exacerbates the need for in-process monitoring and control of critical product attributes, in order to guarantee safety, efficacious and continuous supply of this CBT. There are therefore mutual industrial and regulatory motivations for high throughput, non-invasive and non-destructive sensors, amenable to integration in an enclosed automated cell culture system. While a plethora of analytical methods is available for direct characterization of cellular parameters, only a few satisfy the requirements for online quality monitoring of industrial-scale bioprocesses. [Continues.
    corecore