294 research outputs found
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Light modulation of electric field driven semiconductor micromotors
The future micro/nanorobots require high degrees of freedom in motion control to perform complex tasks by individuals or by a swarm. It remains a great challenge to control the motions of an individual nanomachine amidst many, to switch the operation modes facilely, and it is even more difficult to actuate several components of a nanomachine coordinately for purposed actions. This high degree of versatility is essential for the future micro/nanorobots and requires investigation of innovative actuation mechanisms. In this dissertation, we report our recent finding about a new approach combining two types of stimulation to achieve such goal. The micromotors being studied are made of semiconductor silicon nanowires. Mechanical motion of the motors is driven by several types of AC electric field. Meanwhile, the electrical property of the nanowires can be locally and instantaneously modulated by visible light illumination in a reversible manner. We demonstrate that visible light is able to change the electric polarization of semiconductor nanowires under AC electric field, and reflected by the dramatic change of mechanical motions with very rich configurations. Under a rotating electric field, the rotation speed of semiconductor Si nanowires in electric fields can instantly increase, decrease, and even reverse the orientation by light illumination in the visible to infrared regime at various AC E-field frequencies. Under a linear AC electric field, instantaneous change of alignment direction and speed of semiconductor nanowires is observed under visible-light exposure. With theoretical analysis and simulation, the working principle can be attributed to the optically tuned imaginary-part (out-phase) and real-part (in-phase) electrical polarization of a semiconductor nanowire in aqueous suspension. Based on the understanding of this system, we further propose a new approach to control the semiconductor micromotor via light tunable dielectrophoresis. Localized control of collective behavior in a highly density silicon nanowire suspension is also investigated. Finally, we demonstrated how to utilize the mechanical motion at microscale for practical application of biosensing.Materials Science and Engineerin
Modelling bacterial biofilms in spatially heterogeneous environments
Biofi lms are communities of one or more species of microorganism which have
adhered both together and to a surface. Biofi lms are ubiquitous in nature,
with up to 80% of bacterial life on earth estimated to be found in a biofi lm.
Bacterial biofi lms are far more resilient to both chemical and physical methods of
removal than their planktonic counterparts, which presents numerous challenges
in both clinical and industrial scenarios. Therefore, further research into the
underlying mechanisms of how these biofi lms develop and survive is essential.
This thesis aims to do so via the implementation of various computational
modelling techniques.
Currently, most computational modelling of biofi lms is done under somewhat
idealised conditions, such as uniform antibiotic concentrations and mono-species
bio lms, which do not always reflect the complex conditions found in vivo.
This thesis therefore also aims to address this problem by using computational
models to understand how biofi lms proliferate and resist methods of removal
in spatially heterogeneous environments, such as chemical gradients of nutrients
and antibiotics, or non-uniform
flow fi elds. The thesis takes the form of three
distinct projects, which are linked together by this common theme of spatial
non-uniformity.
Presented fi rst is an investigation into the coupling between nutrient availability
and growth-dependent antibiotic susceptibility. This project uses a simple 1D
Monte-Carlo model to simulate the advancement of a bacterial population along a
spatial antibiotic concentration gradient. Bacterial replication consumes nutrients
which in turn lowers the local growth rate, altering the antibiotic susceptibility.
The results highlight the differing outcomes for antibiotics which target either
slow-growing or fast-growing cells.
Following this, the next project investigates the initial stages of biofi lm formation
on a surface. This chapter involves a pair of complementary models, a
deterministic one, involving a system of differential equations; and a stochastic
one, where the individual bacteria are simulated using a modifi ed Γ-leaping
algorithm, both again in 1D. By modifying the rates for certain actions
which the bacteria undertake, the models predict that under certain conditions
biofi lm formation is highly predictable, but for other parameter regimes, bio lm
formation becomes more stochastic.
In the third project, the stochastic biofi lm formation model described above
is extended to develop a model for the formation of biofi lms on a surface
which leaches an antimicrobial compound into the surrounding environment,
similar to current antifouling coatings used to prevent marine biofouling in the
shipping industry. A key difference in this model is the inclusion of multiple
bacterial species, each with differing resistances to the applied biocide, intended
to represent the biodiversity found in a typical marine environment.
Finally, a computational
fluid dynamics model is presented, which is used to
model the interaction between a micro-structured surface featuring shark skin-like
riblets and an enveloping biofi lm, when exposed to an external
flow fi eld
of various incident
flow angles. These riblets are a contemporary solution to
reducing hydrodynamic drag, e.g., on ship hulls, but are only effective when their
physical shape is unobstructed. Investigating how misaligned riblets can impede,
or even prevent, the sloughing of bio lm matter is therefore crucial to optimising
their performance
Micro/Nano Structures and Systems
Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability is a comprehensive guide that explores the various aspects of micro- and nanostructures and systems. From analysis and design to manufacturing and reliability, this reprint provides a thorough understanding of the latest methods and techniques used in the field. With an emphasis on modern computational and analytical methods and their integration with experimental techniques, this reprint is an invaluable resource for researchers and engineers working in the field of micro- and nanosystems, including micromachines, additive manufacturing at the microscale, micro/nano-electromechanical systems, and more. Written by leading experts in the field, this reprint offers a complete understanding of the physical and mechanical behavior of micro- and nanostructures, making it an essential reference for professionals in this field
Photonic Sensors Based on Integrated Ring Resonators
This thesis investigates the application of integrated ring resonators to different sensing applications. The sensors proposed here rely on the principle of optical whispering gallery mode (WGM) resonance shifts of the resonators. Three distinct sensing applications are investigated to demonstrate the concept: a photonic seismometer, an evanescent field sensor, and a zero-drift Doppler velocimeter. These concepts can be helpful in developing lightweight, compact, and highly sensitive sensors. Successful implementation of these sensors could potentially address sensing requirements for both space and Earth-bound applications. The feasibility of this class of sensors is assessed for seismic, proximity, and vibrational measurements
Systematic Approaches for Telemedicine and Data Coordination for COVID-19 in Baja California, Mexico
Conference proceedings info:
ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologies
Raleigh, HI, United States, March 24-26, 2023
Pages 529-542We provide a model for systematic implementation of telemedicine within a large evaluation center for COVID-19 in the area of Baja California, Mexico. Our model is based on human-centric design factors and cross disciplinary collaborations for scalable data-driven enablement of smartphone, cellular, and video Teleconsul-tation technologies to link hospitals, clinics, and emergency medical services for point-of-care assessments of COVID testing, and for subsequent treatment and quar-antine decisions. A multidisciplinary team was rapidly created, in cooperation with different institutions, including: the Autonomous University of Baja California, the Ministry of Health, the Command, Communication and Computer Control Center
of the Ministry of the State of Baja California (C4), Colleges of Medicine, and the College of Psychologists. Our objective is to provide information to the public and to evaluate COVID-19 in real time and to track, regional, municipal, and state-wide data in real time that informs supply chains and resource allocation with the anticipation of a surge in COVID-19 cases. RESUMEN Proporcionamos un modelo para la implementación sistemática de la telemedicina dentro de un gran centro de evaluación de COVID-19 en el área de Baja California, México. Nuestro modelo se basa en factores de diseño centrados en el ser humano y colaboraciones interdisciplinarias para la habilitación escalable basada en datos de tecnologías de teleconsulta de teléfonos inteligentes, celulares y video para vincular hospitales, clínicas y servicios médicos de emergencia para evaluaciones de COVID en el punto de atención. pruebas, y para el tratamiento posterior y decisiones de cuarentena. Rápidamente se creó un equipo multidisciplinario, en cooperación con diferentes instituciones, entre ellas: la Universidad Autónoma de Baja California, la Secretaría de Salud, el Centro de Comando, Comunicaciones y Control Informático.
de la Secretaría del Estado de Baja California (C4), Facultades de Medicina y Colegio de Psicólogos. Nuestro objetivo es proporcionar información al público y evaluar COVID-19 en tiempo real y rastrear datos regionales, municipales y estatales en tiempo real que informan las cadenas de suministro y la asignación de recursos con la anticipación de un aumento de COVID-19. 19 casos.ICICT 2023: 2023 The 6th International Conference on Information and Computer Technologieshttps://doi.org/10.1007/978-981-99-3236-
Development of a compact wireless SAW Pirani vacuum microsensor with extended range and sensitivity
Vakuumsensoren haben nach wie vor einen begrenzten Messbereich und erfordern eine aufwendige Verkabelung sowie eine komplexe Integration in Vakuumkammern. Ein kompakter Sensor, der in der Lage ist, den Erfassungsbereich zwischen Hochvakuum und Atmosphärendruck zu erweitern und dabei drahtlos zu arbeiten, ist äußerst wünschenswert. Der Schwerpunkt dieser Arbeit liegt auf dem Entwurf, der Simulation, der Herstellung und der experimentellen Validierung eines drahtlosen kompakten Vakuum-Mikrosensors mit erweiterter Reichweite und Empfindlichkeit. Zunächst wurde ein neuer Sensor unter Verwendung vorhandener und neu entwickelter Komponenten entworfen. Zweitens wurden die Sensorkomponenten simuliert, um ihre Parameter zu optimieren. Drittens wurde ein Prototyp unter Verwendung der verfügbaren Mikrobearbeitungs- und Halbleitertechnologien hergestellt und montiert. Viertens wurde der Prototyp unter Umgebungs- und Vakuumbedingungen charakterisiert, um seine Leistungen zu validieren.
Für das Wandlerprinzip wurden zwei Techniken kombiniert, nämlich Pirani-Sensorik und akustische Oberflächenwellen. Das Design der Sensorkomponenten bestand aus vier Einheiten: Sensoreinheit, Heizeinheit, Abfrageeinheit und Gehäuse. Alle Einheiten wurden in einen kompakten Würfel eingebaut. Einige Komponenten wurden neu entwickelt, während andere gekauft, modifiziert und dann miteinander verbunden wurden. Die Sensoreinheit besteht aus einem neuen Chip mit verbesserter Sensorleistung dank eines optimierten Verhältnisses von Oberfläche zu Volumen. Die Heizeinheit wurde aus zwei induktiv gekoppelten Spulen und der zugehörigen Konditionierungselektronik zusammengesetzt. Die Abfrageeinheit wurde mit einer Mikro-Patch-Antenne hergestellt. Ein würfelförmiges Polymergehäuse wurde entwickelt, um alle Komponenten in einer Vakuumkammer unterzubringen.
Zweitens wurde die Simulation des Verhaltens der Sensorkomponenten behandelt. Die für die Druckmessung verantwortliche Wärmeübertragung des Sensorchips wurde vom Hochvakuum bis zum Atmosphärendruck untersucht, um seine Abmessungen zu optimieren. Die Verwendung eines hängenden Lithium-Niobat-Chips mit Y-Z-Schnitt und einem TCF von 94 ppm/K führte zu einer verbesserten Leistung in einem Messbereich zwischen \num{d-4}~Pa und \num{e5}~Pa. Die elektronische Kopplung der Heizspulen wurde ebenfalls simuliert, um die Leistungsübertragung und den Kopplungsabstand zu optimieren.
Der dritte Teil betrifft die Herstellungs- und Montageschritte des Prototyps unter Verwendung der verfügbaren Halbleitertechnologien und -ausrüstung. Ein SAW Chip wurde mit einer 100~nm dicken Goldschicht an der Unterseite gesputtert, um den Heizwiderstand zu bilden, und mit Hilfe von Drahtbonding elektrisch mit dem Rest des Sensors verbunden. Es wurde eine Leiterplatte vorbereitet, die die Heiz- und Sensoreinheit enthält. Ein kubisches Gehäusewurde aus PTFE hergestellt.
Viertens wurden die Sensorkomponenten zunächst separat charakterisiert, um ihre Leistungen zu überprüfen, und dann zusammen unter Umgebungsbedingungen. Später wurde der Sensor im Vakuum integriert, und es wurde ein druckabhängiges Verhalten des Sensorchips beobachtet.
Die Relevanz eines drahtlosen Übertragungsverfahrens wurde den herkömmlichen drahtgebundenen Methoden gegenübergestellt. Die Ergebnisse der experimentellen Arbeiten außerhalb und innerhalb des Vakuums zeigten die Machbarkeit und Relevanz des neuen Konzepts
Innovative designs and applications of Janus micromotors with (photo)-catalytic and magnetic motion
El objetivo principal de esta Tesis Doctoral es el diseño y desarrollo de micromotores Janus biocompatibles y
su aplicación en ámbitos relevantes de la salud y de la protección medioambiental. Los micromotores Janus
son dispositivos en la microescala autopropulsados que tienen al menos dos regiones en su superficie con
diferentes propiedades físicas y químicas, lo que les convierte en una clase distintiva de materiales que pueden
combinar características ópticas, magnéticas y eléctricas en una sola entidad. Como la naturaleza del
micromotor Janus -el dios romano de las dos caras- los objetivos de esta Tesis Doctoral presentan naturaleza
dual y comprenden desarrollos de química fundamental y de química aplicada. En efecto, por una parte, el
objetivo central aborda el diseño, síntesis y ensamblaje, así como la caracterización de micromotores Janus
poliméricos propulsados por mecanismos (foto)-catalíticos y/o accionados por campos magnéticos. Por otra
parte, el objetivo central implica la aplicación de los micromotores desarrollados para resolver desafíos sociales
relevantes en los ámbitos químico-analítico, biomédico y ambiental.
Partiendo de estas premisas, en la primera parte de la Tesis Doctoral, se sintetizaron micromotores Janus de
policaprolactona propulsados químicamente integrando nanomateriales para el diseño de sensores móviles
para la detección selectiva de endotoxinas bacterianas. De esta forma, el movimiento autónomo del micromotor
mejora la mezcla de fluidos y la eficacia de las reacciones implicadas permitiendo detectar el analito en pocos
minutos, incluso en muestras viscosas y medios donde la agitación no es posible. Además, esta autopropulsión
es altamente compatible con su empleo en formatos ultra-miniaturizados para el desarrollo de futuros
dispositivos portátiles en el marco de la tecnología point of care para aplicaciones clínicas y agroalimentarias.
Con el fin de incrementar su biocompatibilidad para aplicaciones in vivo, en una segunda etapa de la Tesis
Doctoral, se diseñaron micromotores Janus con propulsión autónoma utilizando luz visible para la eliminación
de toxinas relevantes en procesos inflamatorios. El fenómeno autopropulsivo del micromotor y su capacidad de
interacción con agentes tóxicos condujo a metodologías más rápidas y eficaces infiriéndose un futuro
prometedor de estos micromotores para el tratamiento del shock séptico o intoxicación. En una tercera etapa,
se sintetizaron micromotores propulsados por campos magnéticos. Estos micromotores utilizan una
aproximación elegante de propulsión, exenta del empleo de combustibles químicos tóxicos como sucede en la
propulsión catalítica y, en consecuencia, biocompatible. Asimismo, este mecanismo propulsivo permite
controlar e incluso programar su trayectoria para aplicaciones que requieran de un guiado y de un control
preciso de esta. De manera específica, estos micromotores han sido aplicados en esta Tesis Doctoral para la
liberación controlada de fármacos en el tratamiento de cáncer pancreático y como elementos de remediación
ambiental en la eliminación de agentes nerviosos en aguas contaminadas
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