Design and implementation of a control system for use of galvanometric scanners in laser micromachining applications

In the recent years, laser machining technology has been used widely in industrial applications usually with the aim of increasing the production capability of mass production lines - especially for fast marking, engraving type of applications where speed is an important concern - or manufacturing quality of a certain facility by increasing the level of accuracy in material processing applications such as drilling, cutting; or any scientific research oriented work where high precision machining of parts in sub millimeter scale might be required. A galvanometric scanner is a high precision device that is able to steer a laser beam with a mirror attached to a motor, whose rotor angular range is usually limited with tens of degrees in both directions of rotation; and position is controlled either by voltage or current. Due to their lightness, the rotor and the mirror can move very fast, allowing fast marking (burning out) operation with the laser beam. This can be evaluated as a great advantage compared to slower mechanical appliances used for cutting/machining of different materials. This study concentrates on the analysis of galvanometric scanner system components; and the design and implementation of a hardware and software based control system for a dual-axis galvo setup; and their adaptation for use in laser micromachining applications either as a standalone system or a modular subsystem. Analysis part of the thesis work contains: evaluation of dominant laser micromachining techniques, an overview of the galvanometric scanner system based approach and related components (e.g. electromechanical, electrical, optical), understanding of working principles and related simulation work, compatibility issues with the target micromachining applications. Design part of the thesis work includes: the design and implementation of electronic controller board, intermediate drive electronics stage, microcontroller programming for machining control algorithm, interfacing with graphical user interface based control software and production of necessary mechanical parts. The study has been finalized with experimental work and evaluation of obtained results. The results of these studies are promising and motivate the use of laser galvanometric scanner systems in laser micromachining applications

Development of high-speed imaging techniques for C. elegans nervous system studies

We report high-speed imaging techniques for C. elegans nervous systems studies. We introduce C. elegans, the main model organism in this dissertation, and neuroscientific and biomedical studies using C. elegans involving calcium imaging, nerve regeneration, and drug screening. We review technologies including confocal microscopy and microfluidic devices used in the neuroscientific and biomedical studies We discuss development of a high-speed laser scanning confocal microscope capable of flexible control of imaging conditions, fast imaging speed, and large field-of-view. We provides the design principles used in the development of the confocal microscope including the optical, electrical, and software implementation, and the details of the confocal microscope we built based on the design principles. We present the performance characterization of the confocal microscope, then a few sample images obtained with the confocal microscope. We present development of time-lapse volumetric confocal imaging of whole animal C. elegans Ca²⁺ dynamics. We provide the design of the time-lapse volumetric confocal imaging system including a microfluidic device to accommodate the whole animal within the field-of-view of the imaging system. We examine the feasibility of the volumetric confocal imaging of a whole animal, and demonstrate imaging of the whole animal C. elegans neurons’ response to NaCl within a 630 × 150 × 25 μm³ volume at 2 Hz rate. We report a high-throughput automated imaging platform for C. elegans nerve regeneration study. We describe the design of the automated imaging platform and the automation flow, and characterizes the performance of the platform. The imaging platform can obtain high-resolution 3D confocal images of 20 animals in 10 minutes. We show sample images of C. elegans anterior lateral microtubule nerve regeneration examples acquired via the automated imaging platform. We demonstrate a planar laser activated neuronal scanning platform (PLANS), a high-throughput animal examination system for drug screening. We explain the construction of PLANS involving the optics, the microfluidic device, and the electronics. The PLANS system can scan an animal in less than 5 ms with a spatial sampling resolution of 3 μm FWHM. We show sample scanning results of a Huntington’s disease model of C. elegans. We summarize the studies discussed in this dissertation, and suggest relevant future research to follow up on the studies.Electrical and Computer Engineerin

Spins in Thin Films and Nanodevices

The central theme of this work is the engineering of devices and materials that exhibit spin dependent phenomena. In particular, the spin orientation of charge carriers can play a central role in transport, especially in magnetic or other spin correlated media. Propagation of charge carriers with net spin results in a transfer of angular momentum that can excite static and dynamical states in active device elements. To utilize such phenomena in practical devices, new mew means of device characterization and optimization must be developed. To that end, we have performed experiments which elucidate some of the mechanisms underlying spin dependent transport phenomena.;We report the observation of hysteretic synchronization of point contact spin torque nano-oscillators (STNOs) by a microwave magnetic field. The hysteresis was asymmetric with respect to the frequency detuning of the driving signal, and appeared in the region of a strong dependence of the oscillation frequency on the bias current. Theoretical analysis showed that hysteretic synchronization occurred when the width of the synchronization range, enhanced by the oscillator\u27s nonlinearity, became comparable to the dissipation rate, while the observed asymmetry was a consequence of the nonlinear dependence of frequency on the bias current.;Another emergent phenomenon was a series of fractional synchronization regimes in a STNO driven by a microwave field. These regimes are characterized by rational relations between the driving frequency and the frequency of the oscillation. Analysis based on the phase model of auto-oscillator indicates that fractional synchronization becomes possible when the driving signal breaks the symmetry of the oscillation, while the synchronization ranges are determined by the geometry of the oscillation orbit. Measurements of fractional synchronization were utilized to obtain information about the oscillation characteristics in nanoscale systems not accessible to direct imaging techniques.;Oxidation in magnetic nanosystems can result in changes of the magnetic ordering of active layers in devices, resulting in degraded device performance. We demonstrate that magnetic multilayer nanopillars can be efficiently protected from oxidation by coating with silicon. Both the protected and the oxidized nanopillars exhibited an increase of reversal current at cryogenic temperatures. However the magnetic excitation onset current increased only in the oxidized samples. We show that oxidized nanopillars exhibit anomalous switching statistics at low temperature, providing a simple test for the quality of magnetic nanodevices.;We studied exchange bias in magnetic multilayers incorporating antiferromagnet CoO doped with up to 35 atomic percent of Pt. The exchange bias increased with doping in epitaxial films, but did not significantly change in polycrystalline films at the lowest measured temperature of 5 K, and decreased at higher temperatures. We explain our results by the increased granularity of the doped antiferromagnetic films, resulting in simultaneous enhancement of the uncompensated spin density and reduction of the magnetic stability of antiferromagnetic grains.;Finally, we demonstrate the growth of Bi2Se3, a material known as a topological insulator (TI). The structural and electronic properties of Bi2Se3 films grown on Al2O 3 (110) by molecular beam epitaxy were investigated. The epitaxial films grew in the Frank-van der Merwe mode and were c-axis oriented. They exhibited the highest crystallinity, the lowest carrier concentration, and optimal stoichiometry at a substrate temperature of 200 .C determined by the balance between surface kinetics and desorption of selenium. The crystallinity of the films improved with increasing selenium/bismuth flux ratio

Defining cellular microenvironments using multiphoton lithography

textTo understand the chemistry of life processes in detail is largely a challenge of resolving them in their native, cellular environment. Cell culture, first developed a century ago, has proven to be an essential tool for reductionist studies of cellular biochemistry and development. However, for the technology of cell culture to move forward and address increasingly complex problems, in vitro environments must be refined to better reflect the cellular environment in vivo. This dissertation work has focused on the development of methods to define cellular microenvironments using the high resolution, 3D capabilities of multiphoton lithography. Here, site-specific photochemistry using multiphoton excitation is applied to the photocrosslinking of proteins, providing the means to organize bioactive species into well-defined 3D microenvironments. Further, conditions have been identified that enable microfabrication to be performed in the presence of cells -- allowing cell outgrowth and motility to be directed in real time. In addition to the intrinsic chemical functionality of microfabricated protein structures, 3D protein matrices are shown to respond mechanically to changes in the chemical environment, enabling new avenues for micro-scale actuation to be explored. Complex 2D and 3D protein photocrosslinking is further facilitated by integrating transparency and automated reflectance photomasks into the fabrication system. These advances could be transformative in efforts to fabricate precise cellular scaffolding that replicates the morphological (and potentially biochemical) features of in vivo tissue microenvironments. Finally, these methods are applied to the study of microorganism behavior with single-cell resolution. Microarchitectures are designed that allow the position and motion of motile bacterial to generate directional microfluidic flow -- providing a foundation to develop micro-scale devices powered by cells.Chemistry and BiochemistryBiochemistr

Metasurface-enhanced Light Detection and Ranging Technology

Deploying advanced imaging solutions to robotic and autonomous systems by mimicking human vision requires simultaneous acquisition of multiple fields of views, named the peripheral and fovea regions. Low-resolution peripheral field provides coarse scene exploration to direct the eye to focus to a highly resolved fovea region for sharp imaging. Among 3D computer vision techniques, Light Detection and Ranging (LiDAR) is currently considered at the industrial level for robotic vision. LiDAR is an imaging technique that monitors pulses of light at optical frequencies to sense the space and to recover three-dimensional ranging information. Notwithstanding the efforts on LiDAR integration and optimization, commercially available devices have slow frame rate and low image resolution, notably limited by the performance of mechanical or slow solid-state deflection systems. Metasurfaces (MS) are versatile optical components that can distribute the optical power in desired regions of space. Here, we report on an advanced LiDAR technology that uses ultrafast low FoV deflectors cascaded with large area metasurfaces to achieve large FoV and simultaneous peripheral and central imaging zones. This technology achieves MHz frame rate for 2D imaging, and up to KHz for 3D imaging, with extremely large FoV (up to 150{\deg}deg. on both vertical and horizontal scanning axes). The use of this disruptive LiDAR technology with advanced learning algorithms offers perspectives to improve further the perception capabilities and decision-making process of autonomous vehicles and robotic systems.Comment: 25pages, 18 figures. Including supplementary material

RAPID Lithography: Photopolymerization Characterization and Initiation Kinetics

In order to improve upon the resolution of photolithography, a technique that is used to produce features for today's micro and nanodevices, techniques must move beyond e-beam and deep-UV sources. Multiphoton absorption polymerization (MAP) uses near-infrared light for the creation of complex, three-dimensional features on the sub-100 nm scale. The resolution of MAP can be enhanced further using a two-beam technique called resolution augmentation through photo-induced deactivation (RAPID) to the reach feature sizes as small as 40 nm. The mechanism and kinetics of photo-induced deactivation are not well understood. To better understand these processes, studies of different photoinitiators have been performed. We find that some photoinitiators are so efficient at deactivation that they are capable of undergoing self-deactivation by addition of another photon from the excitation source. This phenomenon is manifested in a polymerization trend in which feature size has a proportional velocity (PROVE) dependence, the opposite of the conventional velocity dependence. We also demonstrate that the velocity dependence can also be tuned between PROVE and conventional dependences. Kinetic models have been formulated to account for the observed deactivation. By reconciling experimental data for some sample photoinitiators with the kinetic model through the use of simulations, kinetic rate constants are determined. The self-deactivation efficiency of each photoinitiator was determined. The lifetimes of intermediates in the radical photopolymerization process were also determined. The kinetic rate constants associated with photoinitiators should allow for the customization of photoinitiators for specific applications and make RAPID a more efficient process capable of reaching resolution on the level of 30 nm and below

Design of LCOS microdisplay backplanes for projection applications

De evolutie van licht emitterende diodes (LED) heeft ervoor gezorgd dat het op dit moment interessant wordt om deze componenten als lichtbron te gebruiken in projectiesystemen. LED’s hebben belangrijke voordelen vergeleken met klassieke booglampen. Ze zijn compact, ze hebben een veel grotere levensduur en ogenblikkelijke schakeltijden, ze werken op lage spanningen, etc. LED’s zijn smalbandig en kunnen een groterekleurenbereik realiseren. Ze hebben momenteel echter een beperkte helderheid. Naast de lichtbron is het type van de lichtklep ook bepalend voor de kwaliteit van een projectiesysteem. Er bestaan verschillende lichtkleptechnologieën waaronder die van de reflectieve LCOS-panelen. Deze lichtkleppen kunnen zeer hoge resoluties hebben en wordenvaak gebruikt in kwalitatieve, professionele projectiesystemen. LED’s zijn echter totaal verschillend van booglampen. Ze hebben een andere vorm, package, stralingspatroon, aansturing, fysische en thermische eigenschappen, etc. Hoewel er een twintigtal optische architecturen bekend zijn voor reflectieve beeldschermen (met een booglamp als lichtbron), zijn ze niet geschikt voor LED-projectoren en moeten nieuwe optische architecturen en een elektronische aansturing ontwikkeld worden. In dit doctoraat werd er hieromtrent onderzoek gedaan. Er werd uiteindelijk een driekleurenprojector (R, G, B) met een efficiënt LED-belichtingssysteem gebouwd met twee LCOS-lichtkleppen. Deze LEDprojector heeft superieure eigenschappen (zeer lange levensduur, beeldkwaliteit, etc.) en een matige lichtopbrengst

Custom-Designed Biohybrid Micromotor for Potential Disease Treatment

Micromotors are recognized as promising candidates for untethered micromanipulation and targeted cargo transport. Their future application is, however, hindered by the low efficiency of drug encapsulation and their poor adaptability in physiological conditions. To address these challenges, one potential solution is to incorporate micromotors with biological materials as the combination of functional biological entities and smart artificial parts represents a manipulable and biologically friendly approach. This dissertation focuses on the development of custom-designed micromotors combined with sperm and their potential applications on targeted diseases treatment. By means of 2D and 3D lithography methods, microstructures with complex configurations can be fabricated for specific demands. Bovine and human sperm are both for the first time explored as drug carriers thanks to their high encapsulation efficiency of hydrophilic drugs, their powerful self-propulsion and their improved drug-uptake relying on the somatic-cell fusion ability. The hybrid micromotors containing drug loaded sperm and constructed artificial enhancements can be self-propelled by the sperm flagella and remotely guided and released to the target at high precision by employing weak external magnetic fields. As a result, micromotors based on both bovine and human sperm show significant anticancer effect. The application here can be further broadened to other biological environments, in particular to the blood stream, showing the potential on the treatment of blood diseases like blood clotting. Finally, to enhance the treatment efficiency, in particular to control sperm number and drug dose, three strategies are demonstrated to transport swarms of sperm. This research paves the way for the precision medicine based on engineered sperm-based micromotors