Technical session talks from ICRA 2012
TechTalks from event: Technical session talks from ICRA 2012
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Micro and Nano Robots I
Polymer-Based Wireless Resonant Magnetic MicrorobotsWe present a class of Wireless Resonant Magnetic Microactuator (WRMMA) that integrates a polymer spring/body structure with electroplated ferromagnetic masses. The new devices, which we call PolyMites as they are derived from our previous MagMites, are simpler, faster and cheaper to fabricate than the MagMite. Like their predecessor, they are capable of moving on planar surfaces in dry and wet environments. Their improved biocompatibility also extends their potential for biological applications. PolyMites are 500 μm in diameter and 55 μm in height. In air they have attained a speed of 13 mm/s, approximately 26 body lengths per second. PolyMites are capable of micromanipulation on a surface, which is demonstrated by pushing and releasing micro-objects such as polystyrene beads in water.
Three-Dimensional Control of Engineered Motile Cellular MicrorobotsWe demonstrate three-dimensional control with the eukaryotic cell Tetrahymena pyriformis (T. pyriformis) using two sets of Helmholtz coils for xy-plane motion and a single electromagnet for vertical motion. T. pyriformis is modified to have artificial magnetotaxis with internalized magnetite. Since the magnetic fields exerted by electromagnets are relatively uniform in the working space, the magnetite exerts only torque, without translational force, which enabled us to guide the cellâ€™s swimming direction while the swimming force is exerted only by the cellâ€™s motile organelles. A stronger magnetic force was necessary to steer cells to the zÂ¬-axis, and, as a result, a single electromagnet placed just below our sample area is utilized for vertical motion. To track the cellâ€™s positions in the z-axis, intensity profiles of non-motile cells at varying distances from the focal plane are used. During vertical motion along the z-axis, the intensity difference from the background decreases while the cell size increases. Since the cell is pear-shaped, the eccentricity is high during planar motion, but lowers during vertical motion due to the change in orientation. The three-dimensional control of the live organism T. pyriformis as a cellular robot shows great potential to be utilized for practical applications in microscale tasks, such as target transport and cell therapy.
Towards MR-Navigable Nanorobotic Carriers for Drug Delivery into the BrainMagnetic Resonance Navigation (MRN) relies on Magnetic Nanoparticles (MNPs) embedded in microcarriers or microrobots to allow the induction of a directional propelling force by 3D magnetic gradients. These magnetic gradients are superposed on a sufficiently high homogeneous magnetic field to achieve maximum propelling force through magnetization saturation of the MNP. As previously demonstrated by our group, such technique was successful at maintaining microcarriers along a planned trajectory in the blood vessels based on tracking information gathered using Magnetic Resonance Imaging (MRI) sequences from artifacts caused by the same MNPs. Besides propulsion and tracking, the same MNPs can be synthesized with characteristics that can allow for the diffusion of therapeutic cargo carried by these MR-navigable carriers through the Blood Brain Barrier (BBB) using localized hyperthermia without compromising the MRN capabilities. In the present study, an external heating apparatus was used to impose a regional heat shock on the skull of a living mouse model. The effect of heat on the permeability of the BBB was assessed using histological observation and tissue staining by Evans blue dye. Results show direct correlation between hyperthermia and BBB leakage as well as its recovery from thermal damage. Therefore, the proposed navigable agents could be suitable for controlled opening of the BBB by hyperthermia and selective brain drug delivery.
Diamagnetically Levitated Robots: An Approach to Massively Parallel Robotic Systems with Unusual Motion PropertiesUsing large numbers of microrobots to build unique macrostructures has long been a vision in both popular and scientific media. This paper describes a new class of machines, DiaMagnetic Micro Manipulator (DM3) systems, for controlling many small robots. The robots are diamagnetically levitated with zero wear and zero hysteresis, and driven using conventional circuits. Unusual motion properties have been reported in testing these systems, including exceptional open loop repeatability of motion (200 nm rms) and relative speeds (37.5 cm/s or 217 body lengths/s) . A system using 130 micro robots as small as 1.7 mm with densities up to 12.5 robots/cm2 has been demonstrated. This paper reports initial data on robot trajectories, and shows that open loop trajectory repeatabilities on the order of 0.8 micrometers rms or better are feasible in a levitated state compared with 15 micrometers rms repeatability in a non-levitated state with surface contact. These results suggest an encouraging path to complex microrobotic systems with broad capabilities.
Magnetic Micro Actuator with Neutral Buoyancy and 3D Fabrication of Cell Size Magnetized StructureWe have developed two technologies for 3D magnetic microstructures, with a wide size range between 5μm to 2mm. The first technology enables us to obtain density controlled 3D magnetic microstructures. The size is approximately 500μm. In this scale, controlling density is vital for magnetic micro actuators, because the effect of gravity is strong. To adjust density, we developed the worldâ€™s first â€œdensity controllable magnetically photocurable (DMPC) polymer.â€ The DMPC polymer is a mixture of hollow microcapsules (density, 0.03 g/cm<sup>3</sup>), magnetic particles, and photocurable polymer. We can obtain desired relative density between 0.5 to 1.7 by adjusting the concentration of microcapsules. In addition, we succeeded in 3D velocity control of a screw-type magnetic micro actuator with neutral buoyancy in water. The delay time was 32msec. In addition, the actuator possessed 6 DOF. The second technology realized a 5μm magnetic micro actuator, which is a combination of a 3D transparent structure and 2D magnetic structure. Various photocurable polymers can be applied as the 2D structure in this process, although we used magnetically photocurable polymer in this report. Furthermore, we have succeeded in driving a ferromagnetic micro actuator, whose diameter is as small as 1μm. These two fabrication processes will become key technologies in both medical and life sciences field, because they can supply a wide variety of 3D micro structures with small effort.