29 research outputs found
Modeling and design of an electromagnetic actuation system for the manipulation of microrobots in blood vessels
Tese de mestrado integrado em FĂsica, apresentada Ă Universidade de Lisboa, atravĂ©s da Faculdade de CiĂȘncias, 2015A navegação de nano/microdispositivos apresenta um grande potencial para aplicaçÔes biomĂ©dicas, oferecendo meios de diagnĂłstico e procedimentos terapĂȘuticos no interior do corpo humano. Dada a sua capacidade de penetrar quase todos os materiais, os campos magnĂ©ticos sĂŁo naturalmente adequados para controlar nano/microdispositivos magnĂ©ticos em espaços inacessĂveis. Uma abordagem recente Ă© o uso de um aparelho personalizado, capaz de controlar campos magnĂ©ticos. Esta Ă© uma ĂĄrea de pesquisa prometedora, mas mais simulaçÔes e experiĂȘncias sĂŁo necessĂĄrias para avaliar a viabilidade destes sistemas em aplicaçÔes clĂnicas.
O objectivo deste projecto foi a simulação e desenho de um sistema de atuação eletromagnĂ©tica para estudar a locomoção bidimensional de microdispositivos. O primeiro passo foi identificar, atravĂ©s da anĂĄlise de elementos finitos, usando o software COMSOL, diferentes configuraçÔes de bobines que permitiriam o controlo de dispositivos magnĂ©ticos em diferentes escalas. Baseado nos resultados das simulaçÔes, um protĂłtipo de um sistema de atuação magnĂ©tica para controlar dispositivos com mais de 100 m foi desenhado e construĂdo de raiz, tendo em conta restriçÔes de custos. O sistema consistiu num par de bobines de Helmholtz e rotacionais e um par de bobines de Maxwell dispostas no mesmo eixo. AlĂ©m disso, componentes adicionais tiveram de ser desenhados ou selecionados para preencher os requisitos do sistema. Para a avaliação do sistema fabricado, testes preliminares foram realizados. A locomoção do microrobot foi testada em diferentes direçÔes no plano x-y.
As simulaçÔes e experiĂȘncias confirmaram que Ă© possĂvel controlar a força magnĂ©tica e o momento da força que atuam num microdispositivo atravĂ©s do campos produzidos pelas bobines de Maxwell e Helmholtz, respectivamente. Assim, este tipo de atuação magnĂ©tica parece ser uma forma adequada de transferĂȘncia de energia para futuros microdispositivos biomĂ©dicos.Navigation of nano/microdevices has great potential for biomedical applications, offering a means for diagnosis and therapeutic procedures inside the human body. Due to their ability to penetrate most materials, magnetic fields are naturally suited to control magnetic nano/microdevices in inaccessible spaces. One recent approach is the use of custom-built apparatus capable of controlling magnetic devices. This is a promising area of research, but further simulation studies and experiments are needed to estimate the feasibility of these systems in clinical applications.
The goal of this project was the simulation and design of an electromagnetic actuation system to study the two dimensional locomotion of microdevices. The first step was to identify, through finite element analysis using software COMSOL, different coil configurations that would allow the control of magnetic devices at different scales. Based on the simulation results, a prototype of a magnetic actuation system to control devices with more than 100 m was designed and built from the ground up, taking into account cost constraints. The system comprised one pair of rotational Helmholtz coils and one pair of rotational Maxwell coils placed along the same axis. Furthermore, additional components had to be designed or selected to fulfil the requirements of the system. For the evaluation of the fabricated system, preliminary tests were carried out. The locomotion of a microdevice was tested along different directions in the x-y plane.
The simulations and experiments confirmed that it is possible to control the magnetic force and torque acting on a microdevice through the fields produced by Maxwell and Helmholtz coils, respectively. Thus, this type of magnetic actuation seems to provide a suitable means of energy transfer for future biomedical microdevices
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Medical Imaging of Microrobots: Toward In Vivo Applications
Medical microrobots (MRs) have been demonstrated for a variety of non-invasive biomedical applications, such as tissue engineering, drug delivery, and assisted fertilization, among others. However, most of these demonstrations have been carried out in in vitro settings and under optical microscopy, being significantly different from the clinical practice. Thus, medical imaging techniques are required for localizing and tracking such tiny therapeutic machines when used in medical-relevant applications. This review aims at analyzing the state of the art of microrobots imaging by critically discussing the potentialities and limitations of the techniques employed in this field. Moreover, the physics and the working principle behind each analyzed imaging strategy, the spatiotemporal resolution, and the penetration depth are thoroughly discussed. The paper deals with the suitability of each imaging technique for tracking single or swarms of MRs and discusses the scenarios where contrast or imaging agent's inclusion is required, either to absorb, emit, or reflect a determined physical signal detected by an external system. Finally, the review highlights the existing challenges and perspective solutions which could be promising for future in vivo applications
Frontiers of Medical Micro/Nanorobotics: in vivo Applications and Commercialization Perspectives Toward Clinical Uses
The field of medical micro/nanorobotics holds considerable promise for advancing medical diagnosis and treatment due to their unique ability to move and perform complex task at small scales. Nevertheless, the grand challenge of the field remains in its successful translation towards widespread patient use. We critically address the frontiers of the current methodologies for in vivo applications and discuss the current and foreseeable perspectives of their commercialization. Although no âkiller applicationâ that would catalyze rapid commercialization has yet emerged, recent engineering breakthroughs have led to the successful in vivo operation of medical micro/nanorobots. We also highlight how standardizing report summaries of micro/nanorobotics is essential not only for increasing the quality of research but also for minimizing investment risk in their potential commercialization. We review current patents and commercialization efforts based on emerging proof-of-concept applications. We expect to inspire future research efforts in the field of micro/nanorobotics toward future medical diagnosis and treatment
A comprehensive survey on hybrid communication in context of molecular communication and terahertz communication for body-centric nanonetworks
With the huge advancement of nanotechnology over the past years, the devices are shrinking into micro-scale, even nano-scale. Additionally, the Internet of nano-things (IoNTs) are generally regarded as the ultimate formation of the current sensor networks and the development of nanonetworks would be of great help to its fulfilment, which would be ubiquitous with numerous applications in all domains of life. However, the communication between the devices in such nanonetworks is still an open problem. Body-centric nanonetworks are believed to play an essential role in the practical application of IoNTs. BCNNs are also considered as domain specific like wireless sensor networks and always deployed on purpose to support a particular application. In these networks, electromagnetic and molecular communications are widely considered as two main promising paradigms and both follow their own development process. In this survey, the recent developments of these two paradigms are first illustrated in the aspects of applications, network structures, modulation techniques, coding techniques and security to then investigate the potential of hybrid communication paradigms. Meanwhile, the enabling technologies have been presented to apprehend the state-of-art with the discussion on the possibility of the hybrid technologies. Additionally, the inter-connectivity of electromagnetic and molecular body-centric nanonetworks is discussed. Afterwards, the related security issues of the proposed networks are discussed. Finally, the challenges and open research directions are presented
FABRICATION OF MAGNETIC TWO-DIMENSIONAL AND THREE-DIMENSIONAL MICROSTRUCTURES FOR MICROFLUIDICS AND MICROROBOTICS APPLICATIONS
Micro-electro-mechanical systems (MEMS) technology has had an increasing impact on industry and our society. A wide range of MEMS devices are used in every aspects of our life, from microaccelerators and microgyroscopes to microscale drug-delivery systems. The increasing complexity of microsystems demands diverse microfabrication methods and actuation strategies to realize. Currently, it is challenging for existing microfabrication methodsâparticularly 3D microfabrication methodsâto integrate multiple materials into the same component. This is a particular challenge for some applications, such as microrobotics and microfluidics, where integration of magnetically-responsive materials would be beneficial, because it enables contact-free actuation. In addition, most existing microfabrication methods can only fabricate flat, layered geometries; the few that can fabricate real 3D microstructures are not cost efficient and cannot realize mass production.
This dissertation explores two solutions to these microfabrication problems: first, a method for integrating magnetically responsive regions into microstructures using photolithography, and second, a method for creating three-dimensional freestanding microstructures using a modified micromolding technique. The first method is a facile method of producing inexpensive freestanding photopatternable polymer micromagnets composed NdFeB microparticles dispersed in SU-8 photoresist. The microfabrication process is capable of fabricating polymer micromagnets with 3 ”m feature resolution and greater than 10:1 aspect ratio. This method was used to demonstrate the creation of freestanding microrobots with an encapsulated magnetic core. A magnetic control system was developed and the magnetic microrobots were moved along a desired path at an average speed of 1.7 mm/s in a fluid environment under the presence of external magnetic field. A microfabrication process using aligned mask micromolding and soft lithography was also developed for creating freestanding microstructures with true 3D geometry. Characterization of this method and resolution limits were demonstrated. The combination of these two microfabrication methods has great potential for integrating several material types into one microstructure for a variety of applications
MRI-Based Communication with Untethered Intelligent Medical Microrobots
RESUME Les champs magnĂ©tiques prĂ©sent dans un systĂšme clinique dâImagerie par RĂ©sonance MagnĂ©tique (IRM) peuvent ĂȘtre exploitĂ©s non seulement, afin dâinduire une force de dĂ©placement sur des microrobots magnĂ©tiques tout en permettant lâasservissement de leur position - une technique connue sous le nom de Navigation par RĂ©sonance MagnĂ©tique (NRM), mais aussi pour mettre en Ćuvre un procĂ©dĂ© de communication. Pour des microrobots autonomes Ă©quipĂ©s de senseurs ayant un certain niveau d'intelligence et opĂ©rant Ă l'intĂ©rieur du corps humain, la puissance de transmission nĂ©cessaire pour communiquer des informations Ă un ordinateur externe par des mĂ©thodes prĂ©sentement connues est insuffisante. Dans ce travail, une technique est dĂ©crite oĂč une telle perte de puissance d'Ă©mission en raison de la mise Ă l'Ă©chelle de ces microrobots peut ĂȘtre compensĂ©e par le scanner IRM agissant aussi comme un rĂ©cepteur trĂšs sensible. La technique de communication prend la forme d'une modification de la frĂ©quence du courant Ă©lectrique circulant le long d'une bobine miniature incorporĂ© dans un microrobot. La frĂ©quence du courant Ă©lectrique peut ĂȘtre rĂ©glĂ©e Ă partir d'une entrĂ©e de seuil prĂ©dĂ©terminĂ©e du senseur mis en place sur le microrobot. La frĂ©quence devient alors corrĂ©lĂ©e Ă lâinformation de lâĂ©tat du senseur recueilli par le microrobot et elle est dĂ©terminĂ©e en utilisant l'IRM. La mĂ©thode proposĂ©e est indĂ©pendante de la position et l'orientation du microrobot et peut ĂȘtre Ă©tendue Ă un grand nombre de microrobots pour surveiller et cartographier les conditions physiologiques spĂ©cifiques dans une rĂ©gion plus vaste Ă nâimporte quelle profondeur Ă l'intĂ©rieur du corps.----------ABSTRACT The magnetic environment provided by a clinical Magnetic Resonance Imaging (MRI) scanner can be exploited to not only induce a displacement force on magnetic microrobots while allowing MR-tracking for serving control purpose or positional assessment - a technique known as Magnetic Resonance Navigation (MRN), but also for implementing a method of communication with intelligent microrobots. For untethered sensory microrobots having some level of intelligence and operating inside the body, the transmission power necessary to communicate information to an external computer via known methods is insufficient. In this work, a technique is described where such loss of transmission power due to the scaling of these microrobots can be compensated by the same MRI scanner acting as a more sensitive receiver. A communication scheme is implemented in the form of a frequency alteration in the electrical current circulating along a miniature coil embedded in a microrobot. The frequency of the electrical current could be regulated from a predetermined sensory threshold input implemented on the microrobot. Such a frequency provides information on the level of sensory information gathered by the microrobot, and it is determined using MR imaging. The proposed method is independent of the microrobot's position and orientation and can be extended to a larger number of microrobots for monitoring and mapping specific physiological conditions inside a larger region at any depths within the body
Accurate modelling and positioning of a magnetically-controlled catheter tip
This thesis represents the initial phase of a proposed operator and patient friendly method designed to semi-automate the positioning and directing of an intravascular catheter in the human heart using a variable electromagnetically induced field to control a catheter tip equipped with three tiny fixed magnets oriented in XYZ planes. Here we demonstrate a comprehensive mathematical model which accurately calculates the magnetic field generated by the electromagnet system, and the magnetic torques and forces exerted on a three-magnet tip catheter. From this we have developed an iterative predictive computer algorithm to show the displacement and deflection of the catheter tip. Using an eight variable power electromagnet system around a 250mm sphere of air we have proven the ability of this to accurately move the catheter tip from an initial position to a designated position within the field