Therapies targeting neurodegenerative diseases via brain ventricles and spinal parenchyma face delivery challenges. Systemic administration is ineffective due to the blood-brain barrier, while direct surgical access, especially for multi-site delivery, is highly invasive. The spinal subarachnoid space offers potential for microcatheter-based delivery, but existing robotic catheter technologies are unsuitable due to spinal anatomy constraints. This paper presents a miniaturised and sensorised steerable eversion-growing robot tailored to navigation of the subarachnoid space of the spine. The property of eversion reduces interaction forces with the anatomy, rendering our approach safer than microcatheters that need to be pushed. Our system is capable of real-time tip force estimation with three degrees of freedom (DoF) using fibre Bragg gratings (FBG). Additionally, it incorporates a micro-endoscope and a steerable tip, all within a tiny 2mm outer diameter. The system’s navigation, sensing, and imaging capabilities were evaluated using a realistic up-scaled phantom of the subarachnoid space covering the cervical spine, demonstrating interaction forces within the safe range of 2-5N during phantom navigation. Comparison study of instrument-tissue interactions further approved its clinical relevance, presenting a 73.78% decrease of the mean absolute forces to traditional insertion without the sheath in global measurements.

This paper presents a lumped-parameter dynamic model of a pressure driven eversion robot carrying a catheter through its hollow core. A simulation framework based on the model is developed in MATLAB and is used for understanding the underlying physics, for identifying the regions of operation, and for demonstrating that, for a range of input commands, the catheter can be used as an actuation mechanism for propelling eversion; an approach especially useful for miniaturised systems. Simulations are experimentally validated on the MAMMOBOT system, which is a miniature steerable soft growing robot for early breast cancer detection. It was demonstrated that for most regions of operation experimental results compare well with simulation exhibiting an error less than 4%. Only one region of operation demonstrated larger deviations due possibly to unmodeled dynamics, which will be investigated in future work.

This paper presents the mathematical derivation and experimental validation of a computational model, which accurately predicts static, large-strain deformations of tendon driven non-slender soft-arm manipulators subjected to gravity. The large strain behaviors are captured by employing the Green-Lagrange strain and by deriving analytical expressions for the variation of the equivalent Young modulus of the structure due to the large strains. No simplifying assumptions are made regarding the curvature of the structure, the stretching or the compression. Furthermore the paper proposes an iterative method for numerically solving the resultant non-linear system of coupled differential equations and demonstrates a number of application scenarios. The model is experimentally validated using a set-up comprising one segment of tendon driven soft-arm, which integrates stretchable and compressible hyperelastic (rubber-type) materials into its non-homogeneous back bone structure.

Actuators that are powered, imaged and controlled by Magnetic Resonance (MR) scanners offer the potential of inexpensively providing wireless control of MR-guided robots. Similar to traditional electric motors, the MR scanner acts as the stator and generates propulsive torques on an actuator rotor containing one or more ferrous particles. To generate maximum motor torque while avoiding instabilities and slippage, closed-loop control of the electromagnetic field gradients, i.e., commutation, is required. This paper proposes and demonstrates a method for commutation based on interleaving pulse sequences for rotor tracking and rotor propulsion. Fast rotor tracking is achieved by a new technique utilizing radio-frequency (RF) selective excitation of a properly located fiducial marker by the ferrous particle of the rotor. Optimal marker location is derived and demonstrated to provide accurate estimates of rotor angle. In addition, closed-loop commutation control is shown to increase motor torque and also to enable regulation of rotor angle.

This paper presents the analysis, design, and closed-loop motion control of a mobile microrobotic platform capable of micrometer positioning on a plane. The mobile microrobot, including chassis, actuators, drives, microprocessor, and electronics, is of low cost (less than $20), can be fabricated rapidly and is made of commercially available components. Its motion is induced by centrifugal forces generated by two vibration motors installed inside the platform body. The asynchronous operation of the vibration motors is shown by simulation to result in planar motions of two degrees-of-freedom locally, with micrometer resolution. A motion controller has been designed to generate controlled motions using sets of motor angular velocities. A prototype has been developed and used to validate the motion principle and the controller efficacy. Open loop experiments show that the platform motion resolution is approximately 20 μm, while its speed is greater than 2 mm/s. Closed-loop experiments demonstrate a 5 μm resolution, i.e., a fourfold improvement compared to the open loop experiments. The low cost, the rapid fabrication, and the micrometer motion resolution suggest that this microrobotic platform is a promising solution for low-cost microfactories, where a group of such robots performs high throughput, advanced microassembly of microsystems.

There are many examples of minimally invasive surgery in which tethered robots are incapable of accurately reaching target locations deep inside the body either because they are too large and result in tissue damage or because the tortuosity of the path leads to loss of tip control. In these situations, small untethered magnetically-powered robots may hold the potential to act as delivery vehicles for therapeutic agents. While MRI scanners provide a means to power, control and image such robots as they move throughout the body, a substantial challenge arises if the clinical application requires more than one such robot. The resulting system is underactuated and thus its controllability is in question. This paper presents a simple motion planning algorithm for two magnetic capsules and demonstrates through simulation and experiment that nonlinear fluid damping can be exploited to independently control the positions of the capsules.

This paper presents a novel actuation technology for robotically assisted MRI-guided interventional procedures. Compact and wireless, the actuators are both powered and controlled by the MRI scanner. The design concept and performance limits are described and derived analytically. Simulation and experiments in a clinical MR scanner are used to validate the analysis and to demonstrate the capability of the approach for needle biopsies. The concepts of actuator locking mechanisms and multi-axis control are also introduced.

Magnetic Resonance Imaging (MRI) guided nanorobotic systems that could perform diagnostic, curative and reconstructive treatments in the human body at the cellular and sub-cellular level in a controllable manner have recently been proposed. The concept of a MRI-guided nanorobotic system is based on the use of a MRI scanner to induce the required external driving forces to guide magnetic nanocapsules to a specific target. However, the maximum magnetic gradient specifications of existing clinical MRI systems are not capable of driving superparamagnetic nanocapsules against the blood flow and therefore these MRIs do not allow for navigation. The present paper proposes a way to overcome this critical drawback through the formation of micron size agglomerations where their size can be regulated by external magnetic stimuli. This approach is investigated through modeling of the physics that govern the self-assembly of the nanoparticles. Additionally a computational tool has been developed that incorporates the derived models and performs simulation, visualization and post-processing analysis. Preliminary simulation results demonstrate that external magnetic field causes aggregation of nanoparticles while they flow in the vessel. This is a promising result -in accordance with similar experimental results- and encourages further investigation on the nanoparticle based self-assembly structures for use in nanorobotic drug delivery.

This paper studies the capabilities of a microrobotic platform, driven by vibrating motors, to generate and impart micromanipulation forces of desired type and magnitude. First, an analysis is carried out on the nature of the actuation forces of the motion mechanism of the platform. The results demonstrate that the oscillating nature of these forces does not allow their direct use for micromanipulations. Consequently, further analysis is conducted to identify the conditions, under which the platform's actuation forces can be exploited for micromanipulations. To this end, a dynamic model of a single-dimensional pushing operation is developed, comprising the dynamics of the platform, the manipulator and the object. It is demonstrated by simulation that the forces imparted on the manipulated object depend on the physical parameters of the platform-manipulator system. Accordingly, a set of nonlinear equations involving platform-manipulator system parameters, is formulated that describes the conditions for developing micromanipulation forces of appropriate type and magnitude. The solution of this set of equations yields a range of parameter values, which are used as guidelines in the design and construction of a manipulator that is capable of applying smooth and controllable forces to manipulated objects. Using the parameter values suggested by the developed analysis, a needle type manipulator, appropriate for force feedback applications, is designed, built, and mounted on an experimental prototype of the microrobotic platform. Using this manipulator, experiments demonstrate the force capabilities of the microrobotic platform and verified the analytical and simulation results.

In this paper a study is conducted on the force capabilities of centripetal force actuated microrobotic platforms. The aim is to exploit the centripetal forces generated by platform mounted vibrating micro-motors for micromanipulation purposes. First, an overview of the platform dynamics and motion capabilities is presented. The type of forces generated by the actuation mechanism as well as due to the impulsive interaction with the working environment are studied. Then design steps are proposed for (i) the reduction or elimination of undesired impulsive forces, (ii) the attenuation of the force ripple transmitted to the manipulated object. The outcome is a smooth, controllable force transmitted to the manipulated object. A cantilever is mounted on the platform and preliminary experiments are conducted.

This paper presents the motion analysis, design and position control of a novel, low cost, sliding micro-robot, which is actuated by centripetal forces generated by robot mounted vibration micro-motors. A new, two-micromotor design of the platform is presented, that improves system energy efficiency, and further does not necessitate for synchronous actuator operation and robot symmetry. The motion behavior of the micro-robot, for asynchronous actuation operation, is expressed analytically and simulation results are presented. A control strategy for microrobot x,thetasz, position control that employs two motor speed controllers, and a platform position controller is designed. The control system performance is evaluated through the simulation of a successful trajectory tracking task. A prototype of the micro-robot has been constructed and is presented

This paper presents the analysis and design of a novel mini-robotic platform that is able to perform translational and rotational sliding with sub-micrometer positioning accuracy and develop velocities up to 1.5 mm/s. The platform actuation system employs vibration micro motors. The dynamic model of the platform and of its actuation system is presented, and analytical expressions are derived which provide design guidelines for the platform. Simulations are performed which verify the analytical results and demonstrate the platform capabilities. The platform design is simple, compact and of low cost. Also the energy supply of the mechanism can be accomplished in an untethered mode using simple means such as single cell batteries.