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

Magnetic motion control and planning of untethered soft grippers using ultrasound image feedback

Soft miniaturized untethered grippers can be used to manipulate and transport biological material in unstructured and tortuous environments. Previous studies on control of soft miniaturized grippers employed cameras and optical images as a feedback modality. However, the use of cameras might be unsuitable for localizing miniaturized agents that navigate within the human body. In this paper, we demonstrate the wireless magnetic motion control and planning of soft untethered grippers using feedback extracted from B-mode ultrasound images. Results show that our system employing ultrasound images can be used to control the miniaturized grippers with an average tracking error of 0.4±0.13 mm without payload and 0.36±0.05 mm when the agent performs a transportation task with a payload. The proposed ultrasound feedback magnetic control system demonstrates the ability to control miniaturized grippers in situations where visual feedback cannot be provided via cameras

Actuation, Sensing And Control For Micro Bio Robots

The continuing trend in miniaturization of technology, advancements in micro and nanofabrication and improvements in high-resolution imaging has enabled micro- and meso-scale robots that have many applications. They can be used for micro-assembly, directed drug delivery, microsurgery and high-resolution measurement. In order to create microrobots, microscopic sensors, actuators and controllers are needed. Unique challenges arise when building microscale robots. For inspiration, we look toward highly capable biological organisms, which excel at these length scales. In this dissertation we develop technologies that combine biological components and synthetic components to create actuation, sensing and assembly onboard microrobots. For actuation, we study the dynamics of synthetic micro structures that have been integrated with single-cell biological organisms to provide un-tethered onboard propulsion to the microrobot. For sensing, we integrate synthetically engineered sensor cells to enable a system capable of detecting a change in the local environment, then storing and reporting the information. Furthermore, we develop a bottom-up fabrication method using a macroscopic magnetic robot to direct the assembly of inorganic engineered micro structures. We showcase the capability of this assembly method by demonstrating highly-specified, predictable assembly of microscale building blocks in a semi-autonomous experiment. These magnetic robots can be used to program the assembly of passive building blocks, with the building blocks themselves having the potential to be arbitrarily complex. We extend the magnetic robot actuation work to consider control algorithms for multiple robots by exploiting spatial gradients of magnetic fields. This thesis makes contributions toward actuation, sensing and control of autonomous micro systems and provides technologies that will lead to the development of swarms of microrobots with a suite of manipulation and sensing capabilities working together to sense and modify the environment

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

Diamonds On The Inside: Imaging Nanodiamonds With Hyperpolarized MRI

Nontoxic nanodiamonds (NDs) have proven useful as a vector for therapeutic drug delivery to cancers and as optical bioprobes of subcellular processes. Despite their potential clinical relevance, an effective means of noninvasively imaging NDs in vivo is still lacking. Recent developments in hyperpolarized MRI leverage an over 10 000 times increase in the nuclear polarization of biomolecules, enabling new molecular imaging applications. This work explores hyperpolarization via intrinsic paramagnetic defects in nanodiamond. We present the results of MRI experiments that enable direct imaging of nanodiamond via hyperpolarized 13C MRI and indirect imaging of nanodiamonds via Overhauser-enhanced MRI. The construction of custom hardware for these experiments is detailed and the path to future in vivo experiments outlined. As nanodiamond has been established as a biocompatible platform for drug delivery, our results will motivate further research into hyperpolarized MRI for tracking nanoparticles in vivo

ALSEP termination report

The Apollo Lunar Surface Experiments Package (ALSEP) final report was prepared when support operations were terminated September 30, 1977, and NASA discontinued the receiving and processing of scientific data transmitted from equipment deployed on the lunar surface. The ALSEP experiments (Apollo 11 to Apollo 17) are described and pertinent operational history is given for each experiment. The ALSEP data processing and distribution are described together with an extensive discussion on archiving. Engineering closeout tests and results are given, and the status and configuration of the experiments at termination are documented. Significant science findings are summarized by selected investigators. Significant operational data and recommendations are also included

42nd Rocky Mountain Conference on Analytical Chemistry

Abstracts from the 42nd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Broomfield, Colorado, July 30 - August 3, 2000

Deck The Walls: Curvature-Mediated Assembly In Confined Nematic Liquid Crystals

Tailoring particle interaction among individual building blocks remains an important challenge in a bottom-up assembly scheme. Elastic interactions in anisotropic fluids can be harnessed for this goal. For my thesis, I am particularly interested in investigating the role of confined liquid crystals as a dispersing medium in driving particle assembly. Nematic liquid crystals (NLCs) are made of rod-like molecules that tend to co-align with their neighbors, in a field called the director field. Anchoring refers to the orientation of the NLC molecules at the boundary. Elasticity arises where the molecules deviate from the director field, in three modes of distortion, splay, twist and bend. When a continuous director field cannot be present everywhere, topological defects form, resulting in small melted regions where the order parameter is undefined. It is well-known that particle with perpendicular anchoring generates associated defects, in the form of a Saturn ring or a dipole. These particles have unique symmetry, analogous to electrostatics. A wall with homeotropic anchoring repels a colloid with the same anchoring; yet by changing the surface topography from planar to concave, one can turn repulsion into attraction. This study is inspired by biology, in the so-called “lock-and-key” interaction. I demonstrate the ability to design precise docking sites, near an undulated boundary with peaks and valleys, for both Saturn rings and dipoles. The domain is engineered to be defect-free in order to avoid strong trapping sites. By tailoring wall curvature, I define sites of attraction and equilibrium loci for colloids that vary from near contact to several particle radii from the boundary. Particles dock in wells of similar radii obeying simple geometric argument that allows particle to maximize splay and bend matching. Wells of large radius stabilized colloids with a distorted Saturn ring. In certain cases, Saturn rings transform to dipolar configurations driven by wall interactions. I can also define sites of repulsion to propel colloids away from these boundaries and find unstable loci from which colloids depart along multiple paths. Small perturbations of colloid position allow selection among these paths. Colloids with different defects interact distinctly with these boundaries, depending on their near field director field. Finally, I demonstrate the ability of a colloid in motion, like “Goldilocks”, to select from wells of different sizes for preferred docking. Landau de Gennes (LdG) simulations, the standard numerical method in solving for the director field without prior knowledge of the position of the defect, are useful tools in elucidating our experimental findings. We have expanded the work to simulate dipoles, as well as mapping the energy landscape to calculate force field to corroborate experimental trajectories. These docking sites are useful tools in building structures. I have observed “eyelashes”, topological dipole chains that follow the local, curved director field. These beget wires that connect the groove corners to topographical features on the cell lid to yield oriented, curvilinear colloidal wires spanning the cell, following the curvature of the director field. As the groove aspect ratio changes, I find different ground states, including the ones that contain defect lines which compete with the corner. Anisotropic particles are natural extension to the spherical particles. I have also shown that ellipsoids have distinct energy landscape that depends on both their aspect ratio and orientation. The interaction relies on near-field director field matching rather than strength of particle-sourced distortion, thus the platform has the potential to be scaled down for nanoscale manipulation. In summary, I study how to guide the formation of reconfigurable structures in NLCs. This was achieved by using boundaries to mold the director field. Docking sites can be exploited for structure formation, such as wiring along the director field. Directing particles toward or away from boundaries provides new tools to steer colloid motion. The abilities to transform defect configuration allows for nano-manufacturing in the defect site

Evolutionary and Physical Properties of Meteoroids

Astrophysical models for meteoroid formation and stellar and planetary evolutions are developed from simulation composition studies