An experimental comparison of path planning techniques applied to micro-sized magnetic agents

Micro-sized agents can be used in applications suchas microassembly, micromanipulation, and minimally invasive surgeries. Magnetic agents such as paramagnetic microparticles can be controlled to deliver pharmaceutical agents to difficult-toaccess regions within the human body. In order to autonomously move these microparticles toward a target/goal area, an obstaclefree path must be computed using path planning algorithms. Several path planning algorithms have been developed in the literature, however, to the best of our knowledge, only few have been employed in an experimental scenario. In this paper we perform an experimental comparison of six path planning algorithms when applied to the motion control of paramagnetic microparticles. Among the families of deterministic and probabilistic path planners we select the ones that we consider the most fundamental, such as: A* with quadtrees, A* with uniform grids, D* Lite, Artificial Potential Field, Probabilistic Roadmap and Rapidly-exploring Random Tree. We consider a 2D environment made by both dynamic and static obstacles. Four scenarios are evaluated. Three metrics such as computation time, length of the trajectory performed by the microparticle, and time to reach the goal are used to compare the planners. Experimental results reveal equivalence between almost all the considered planners in terms of trajectory length and completion time. Concerning the computation time, A* with quadtrees and Artificial Potential Field achieve the best performances

Modeling and design of an electromagnetic actuation system for the manipulation of microrobots in blood vessels

Tese de mestrado integrado em Física, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015A navegação de nano/microdispositivos apresenta um grande potencial para aplicações biomédicas, oferecendo meios de diagnóstico e procedimentos terapêuticos no interior do corpo humano. Dada a sua capacidade de penetrar quase todos os materiais, os campos magnéticos são naturalmente adequados para controlar nano/microdispositivos magnéticos em espaços inacessíveis. Uma abordagem recente é o uso de um aparelho personalizado, capaz de controlar campos magnéticos. Esta é uma área de pesquisa prometedora, mas mais simulações e experiências são necessárias para avaliar a viabilidade destes sistemas em aplicações clínicas. O objectivo deste projecto foi a simulação e desenho de um sistema de atuação eletromagnética para estudar a locomoção bidimensional de microdispositivos. O primeiro passo foi identificar, através da análise de elementos finitos, usando o software COMSOL, diferentes configurações de bobines que permitiriam o controlo de dispositivos magnéticos em diferentes escalas. Baseado nos resultados das simulações, um protótipo de um sistema de atuação magnética para controlar dispositivos com mais de 100 m foi desenhado e construído de raiz, tendo em conta restrições de custos. O sistema consistiu num par de bobines de Helmholtz e rotacionais e um par de bobines de Maxwell dispostas no mesmo eixo. Além 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 direções no plano x-y. As simulações e experiências confirmaram que é possível controlar a força magnética e o momento da força que atuam num microdispositivo através do campos produzidos pelas bobines de Maxwell e Helmholtz, respectivamente. Assim, este tipo de atuação magnética parece ser uma forma adequada de transferência de energia para futuros microdispositivos biomédicos.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

Manipulation of graphitic microparticles in solution with magnetic and electric fields

Contactless manipulation methods for individual microparticles in solution are essential for the controlled study on the microscopic scale. Microparticles derived from graphitic materials, in particular, are of great interest due to their unique material properties. However to date, the manipulation methods for such particles remain widely unexplored. This thesis presents the rst research on the particle manipulation of graphitic microparticles in a diamagnetic solution with electric and magnetic elds. The results show that the particles can be rotationally trapped on a well-de ned plane with a combination of an alternating current electric eld and a static magnetic eld. Furthermore, particle transport and three-dimensional particle trapping can be achieved with static magnetic elds. This research shows that the unique electrical and magnetic properties of graphitic microparticles can lead to novel particle manipulation methods in solution which can be attractive for applications in many areas of research

Design and Implementation of Electromagnetic Actuation System to Actuate Micro/NanoRobots in Viscous Environment

The navigation of Micro/Nanorobots (MNRs) with the ability to track a selected trajectory accurately holds significant promise for different applications in biomedicine, providing methods for diagnoses and treatments inside the human body. The critical challenge is ensuring that the required power can be generated within the MNR. Furthermore, ensuring that it is feasible for the robot to travel inside the human body with the necessary power availability. Currently, MNRs are widely driven either by exogenous power sources (light energy, magnetic fields, electric fields, acoustics fields, etc.) or by endogenous energy sources, such as chemical interaction energy. Various driving techniques have been established, including piezoelectric as a driving source, thermal driving, electro-osmotic force driven by biological bacteria, and micro-motors powered by chemical fuel. These driving techniques have some restrictions, mainly when used in biomedicine. External magnetic fields are another potential power source of MNRs. Magnetic fields can permeate deep tissues and be safe for human organisms. As a result, magnetic fields’ magnetic forces and moments can be applied to MNRs without affecting biological fluids and tissues. Due to their features and characteristics of magnetic fields in generating high power, they are naturally suited to control the electromagnetically actuated MNRs in inaccessible locations due to their ability to go through tiny spaces. From the literature, it can be inferred from the available range of actuation technologies that magnetic actuation performs better than other technologies in terms of controllability, speed, flexibility of the working environment, and far less harm may cause to people. Also, electromagnetic actuation systems may come in various configurations that offer many degrees of freedom, different working mediums, and controllability schemes. Although this is a promising field of research, further simulation studies, and analysis, new smart materials, and the development and building of new real systems physically, and testing the concepts under development from different aspects and application requirements are required to determine whether these systems could be implemented in natural clinical settings on the human body. Also, to understand the latest development in MNRs and the actuation techniques with the associated technologies. Also, there is a need to conduct studies and comparisons to conclude the main research achievements in the field, highlight the critical challenges waiting for answers, and develop new research directions to solve and improve the performance. Therefore, this thesis aims to model and analyze, simulate, design, develop, and implement (with complete hardware and software integration) an electromagnetic actuation (EMA) system to actuate MNRs in the sixdimensional (6D) motion space inside a relatively large region of interest (ROI). The second stage is a simulation; simulation and finite element analysis were conducted. COMSOL multi-physics software is used to analyze the performance of different coils and coil pairs for Helmholtz and Maxwell coil configurations and electromagnetic actuation systems. This leads to the following.: • Finite element analysis (FEA) demonstrates that the Helmholtz coils generate a uniform and consistent magnetic field within a targeted ROI, and the Maxwell coils generate a uniform magnetic gradient. • The possibility to combine Helmholtz and Maxwell coils in different space dimensions. With the ability to actuate an MNR in a 6D space: 3D as a position and 3D as orientation. • Different electromagnetic system configurations are proposed, and their effectiveness in guiding an MNR inside a mimicked blood vessel environment was assessed. • Three pairs of Helmholtz coils and three pairs of coils of Maxwell coils are combined to actuate different size MNRs inside a mimicked blood vessel environment and in 6D. Based on the modeling results, a magnetic actuation system prototype that can control different sizes MNRs was conceived. A closed-loop control algorithm was proposed, and motion analysis of the MNR was conducted and discussed for both position and orientation. Improved EMA location tracking along a chosen trajectory was achieved using a PID-based closed-loop control approach with the best possible parameters. Through the model and analysis stage, the developed system was simulated and tested using open- and closed-loop circumstances. Finally, the closedloop controlled system was concluded and simulated to verify the ability of the proposed EMA to actuate an MN under different trajectory tracking examples with different dimensionality and for different sizes of MNRs. The last stage is developing the experimental setup by manufacturing the coils and their base in-house. Drivers and power supplies are selected according to the specifications that actuate the coils to generate the required magnetic field. Three digital microscopes were integrated with the electromagnetic actuation system to deliver visual feedback aiming to track in real-time the location of the MNR in the 6D high viscous fluidic environment, which leads to enabling closed-loop control. The closed-loop control algorithm is developed to facilitate MNR trajectory tracking and minimize the error accordingly. Accordingly, different tests were carried out to check the uniformity of the magnetic field generated from the coils. Also, a test was done for the digital microscope to check that it was calibrated and it works correctly. Experimental tests were conducted in 1D, 2D plane, and 3D trajectories with two different MNR sizes. The results show the ability of the proposed EMA system to actuate the two different sizes with a tracking error of 20-45 µm depending on the axis and the size of the MNR. The experiments show the ability of the developed EMA system to hold the MNR at any point within the 3D fluidic environment while overcoming the gravity effects. A comparison was made between the results achieved (in simulation and physical experiments) and the results deduced from the literature. The comparison shows that the thesis’s outcomes regarding the error and MNR size used are significant, with better performance relative to the MNR size and value of the error

Parallel manipulation of individual magnetic microbeads for lab-on-a-chip applications

Many scientists and engineers are turning to lab-on-a-chip systems for cheaper and high throughput analysis of chemical reactions and biomolecular interactions. In this work, we developed several lab-on-a-chip modules based on novel manipulations of individual microbeads inside microchannels. The first manipulation method employs arrays of soft ferromagnetic patterns fabricated inside a microfluidic channel and subjected to an external rotating magnetic field. We demonstrated that the system can be used to assemble individual beads (1-3µm) from a flow of suspended beads into a regular array on the chip, hence improving the integrated electrochemical detection of biomolecules bound to the bead surface. In addition, the microbeads can follow the external magnet rotating at very high speeds and simultaneously orbit around individual soft magnets on the chip. We employed this manipulation mode for efficient sample mixing in continuous microflow. Furthermore, we discovered a simple but effective way of transporting the microbeads on-chip in the rotating field. Selective transport of microbeads with different size was also realized, providing a platform for effective sample separation on a chip. The second manipulation method integrates magnetic and dielectrophoretic manipulations of the same microbeads. The device combines tapered conducting wires and fingered electrodes to generate desirable magnetic and electric fields, respectively. By externally programming the magnetic attraction and dielectrophoretic repulsion forces, out-of-plane oscillation of the microbeads across the channel height was realized. Furthermore, we demonstrated the tweezing of microbeads in liquid with high spatial resolutions by fine-tuning the net force from magnetic attraction and dielectrophoretic repulsion of the beads. The high-resolution control of the out-of-plane motion of the microbeads has led to the invention of massively parallel biomolecular tweezers.Ph.D.Committee Chair: Hesketh, Peter; Committee Member: Allen, Mark; Committee Member: Degertekin, Levent; Committee Member: Lu, Hang; Committee Member: Yoda, Minam

Field-Pulse-Induced Annealing of 2D Colloidal Polycrystals

Funding: This work has been funded by the Ministry of Science and Innovation (Grants No. PID2019- 105343GB-I00 and PID2019-105195RA-I00) and the project EUR2021-122001. Acknowledgments: We thank Andrés González-Banciella and Alba Camino for initial experimentsTwo-dimensional colloidal crystals are of considerable fundamental and practical importance. However, their quality is often low due to the widespread presence of domain walls and defects. In this work, we explored the annealing process undergone by monolayers of superparamagnetic colloids adsorbed onto fluid interfaces in the presence of magnetic field pulses. These systems present the extraordinary peculiarity that both the extent and the character of interparticle interactions can be adjusted at will by simply varying the strength and orientation of the applied field so that the application of field pulses results in a sudden input of energy. Specifically, we have studied the effect of polycrystal size, pulse duration, slope and frequency on the efficiency of the annealing process and found that (i) this strategy is only effective when the polycrystal consists of less than approximately 10 domains; (ii) that the pulse duration should be of the order of magnitude of the time required for the outer particles to travel one diameter during the heating step; (iii) that the quality of larger polycrystals can be slightly improved by applying tilted pulses. The experimental results were corroborated by Brownian dynamics simulations.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEMinisterio de Ciencia e Innovación (MCIN)pu

DesigN of a robotic device for automated nucleic acid extraction from biological samples

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2009Includes bibliographical references (leaves: 81-82)Text in English; Abstract: Turkish and Englishxii, 115 leavesNucleic Acids (DNA or RNA) present the genetic structure of the cell or the organism and so are the essential components to make genetic testing. Molecular genetic testing allows one to analyze the genetic structure of an organism to have an idea about the present temporary or hereditary characteristics of the tissue or the whole organism, or specifically define its species. In order to analyze the genetic structure, one must extract and isolate the nucleic acids (NA), which are most of the time inside the cell. The aim of this thesis study is to design and manufacture an automated device with low throughput DNA extraction. Currently, the automated devices used for extraction of genetic material are being manufactured only by the foreign companies. Automated commercial devices used for this purpose were investigated in detail as well as the manual NA extraction hand tools for use in NA extraction. Commercially available components (pipette tip, reagent cartridges, tubes, etc.) to isolate NA were reviewed. Mechanism design process for a low cost and high precision system that requires minimal human operator intervention is carried out. The conceptual designs were developed and the final design of the device was made to comply with the selected components. Electronic equipments (motors, drivers, interface card, etc.) and a suitable graphical user interface compatible with the electronic components was selected and adapted to the system. Finally, a device which is competitive with the commercial ones has been designed and its prototype has been manufactured as a result of this thesis study

Magnetic and Mechanical Properties of Ultrasoft Magnetorheological Elastomers

Magnetorheological elastomers (MREs), composite materials consisting of magnetic particles embedded in a non-magnetic elastomeric matrix, can reversibly modulate their mechanical and magnetic properties through tuning the applied magnetic field H. Recently, ultrasoft MREs have received tremendous attention due to their great potential in biomedical applications. However, the effects of the polymer stiffness and magnetic particle concentration on the magnetic and mechanical properties of ultrasoft MREs still need to be better understood. In this dissertation, the author presents a comprehensive investigation of the magnetic and mechanical properties of ultrasoft MREs as well as their biomedical applications. The effect of polymer stiffness on magnetization reversal of MREs has been investigated using a combination of magnetometry measurements and computational modeling. The magnetic hysteresis loops of the softer MREs exhibit a characteristic pinched loop shape with almost zero remanence and loop widening at intermediate fields that monotonically decreases with increasing polymer stiffness. A two-dipole model that incorporates magneto-mechanical coupling not only confirms that micron-scale particle motion along the applied magnetic field direction plays a defining role in the magnetic hysteresis but also reproduces the observed loop shapes and widening trends for MREs with varying polymer stiffnesses. Measurements of the moduli and surface roughness of ultrasoft MREs at various H’s reveal a sensitive dependence on the magnetic particle concentration and H. As increases from 0 to 23%, ultrasoft MREs at =95.5 kA/m (1200 Oe) show an increase of ≈41×,11×,and 11× in their shear storage, Young’s modulus, and surface roughness, respectively. The moduli and surface roughness can be fit to quadratic functions of and H. The presented magnetic and mechanical properties of ultrasoft MREs provides the framework for applying the MREs as dynamic platforms in biomedical engineering. Ultrasoft MREs have been applied to investigate the response of cells to 2D and 3D dynamic mechanical stimuli. Furthermore, the field-dependent particle motion observed in ultrasoft MREs has inspired an application for creating 3D heterogeneous cellular gradients. This work was performed under the guidance of the author’s thesis advisor, Professor Xuemei Cheng

Therapeutic Magnetic Microcarriers Characterization by Measuring Magnetophoretic Attributes

RÉSUMÉ Des micro/nano-robots sont considérés comme une approche prometteuse pour mener des interventions minimalement invasives. Nous avons proposé d'intégrer des nanoparticules magnétiques dans des agents thérapeutiques ou de diagnostic afin de les contrôler magnétiquement. Un scanner d’imagerie par résonance magnétique (IRM) clinique modifié est utilisé afin de fournir la force motrice qui permet à ces microporteurs magnétiques à naviguer dans le réseau vasculaire humain. En utilisant des séquences spécifiques des gradients de résonance magnétique (MR) cette méthode a été validée dans des travaux de recherche antérieurs. Magnétophorèse est le terme utilisé pour décrire le fait qu'une particule magnétique modifie sa trajectoire sous l'influence d'une force magnétique tout en étant portée par un flux de fluide. Ce mouvement dépend des caractéristiques de la particule magnétique, de sa forme géométrique, des attributs de l'écoulement de fluide et d'autres facteurs. Dans notre méthode proposée, les microporteurs magnétiques peuvent être réalisés de différentes manières, et donc leur réponse sera différente à la même force magnétique et dans les mêmes conditions d'écoulement de fluide. Le résultat du traitement thérapeutique utilisant notre méthode dépend de la sélection adéquate des agents thérapeutiques et/ou de diagnostic à utiliser. Le microporteur magnétique thérapeutique et /ou de diagnostic choisi influe également sur le choix de la séquence des gradients magnétiques que meilleur se ajustement pour un traitement donné. Ce mémoire de maîtrise présente la conception d'un dispositif destiné à évaluer les propriétés magnétophorétiques des agents microporteurs magnétiques thérapeutiques et/ou de diagnostic. Une telle caractérisation est essentielle pour déterminer les séquences optimales des gradients magnétiques pour dévier leur trajectoire à travers des réseaux vasculaires relativement complexes dans le but d'atteindre un objectif prédéfini. Un dispositif microfluidique est fabriqué pour valider la conception. Las vitesses magnétophorétiques sont mesurées et une méthode de suivi simple est proposée. Les résultats des experiences préliminaires indiquent que, malgré certaines limitations, la technique proposée a le potentiel d’être approprié pour caractériser n'importe quel microporteur magnétique thérapeutique et/ou de diagnostic contenant différents taux de nanoparticules magnétiques.----------ABSTRACT Micro/nano robots are considered a promising approach to conduct minimally invasive interventions. We have proposed to embed magnetic nanoparticles in therapeutic or diagnostic agents in order to magnetically control them. A modified clinical Magnetic Resonance Imaging (MRI) scanner is used to provide the driving force that allows these magnetically embedded microcarriers to navigate the vascular human network. By using specific Magnetic Resonance (MR) gradient sequences this method has been validated in previous research works. Magnetophoresis is the term used to describe the fact that a magnetic particle changes its trajectory under the influence of a magnetic force while being carried by a fluid flow. This movement depends on the particle’s magnetic characteristics, the particle’s geometric shape, the fluid flow’s attributes and other factors. In our proposed method, magnetic microcarriers can be produced in several different ways, and so their response will differ to the same magnetic force and fluid flow conditions. The outcome of the therapeutic treatment using our method depends on the adequate selection of the therapeutic and/or diagnosis agents to be used. The selected therapeutic and/or diagnosis magnetic microcarrier also influences the selection of the MR gradient sequence that best fit for a given treatment. This master’s thesis presents the design of a device intended to assess the magnetophoretic properties of magnetic therapeutic microcarriers and/or diagnostic agents. Such characterization is essential for determining the optimal sequences of magnetic gradients to deflect their trajectory through relatively complex vascular networks in order to reach a pre-defined target. A microfluidic device was fabricated to validate the design. Magnetophoretic velocities are measured and a simple tracking method is proposed. The preliminary experimental results indicate that, despite some limitations, the proposed technique has the potential to be appropriate to characterize any drug and/or diagnosis magnetic microcarrier containing different magnetic nanoparticle content