Characteristic Evaluation of a Shrouded Propeller Mechanism for a Magnetic Actuated Microrobot

Abstract

Medical microrobots have been widely used in clinical applications, particularly the spiral type locomotion mechanism, which was recently considered one of the main self-propelling mechanisms for the next medical microrobot to perform tasks such as capsule endoscopy and drug delivery. However, limits in clinical applications still exist. The spiral action of the microrobot while being used for diagnosis may lead to pain or even damage to the intestinal wall due to the exposed mechanisms. Therefore, a new locomotive mechanism, named the shrouded propeller mechanism, was proposed to achieve a high level of medical safety as well as effective propulsive performance in our study. The shrouded propeller mechanism consists of a bare spiral propeller and a non-rotating nozzle. To obtain a high effective propulsive performance, two types of screw grooves with different shapes including the cylindrical screw groove and the rectangular screw groove with different parameters were analyzed using the shrouded model. Two types of magnetic actuated microrobots with different driving modes, the electromagnetic (three-pole rotor) actuated microrobot and the permanent magnet (O-ring type magnet) actuated microrobot were designed to evaluate the performance of the electromagnetic actuation system. Based on experimental results, the Micromachines 2015, 6 1273 propulsive force of the proposed magnetic actuated microrobot with a shrouded propeller was larger than the magnetic actuated microrobot with a bare spiral propeller under the same parameters. Additionally, the shrouded propeller mechanism as an actuator can be used for other medical microrobots for flexible locomotion.

Performance Evaluation of a Magnetically Driven Microrobot for Targeted Drug Delivery

“…Due to the errors in the geometric dimensions of the microrobot and pipeline in the experiment, the microrobot could not be consistent with the simulation results. In addition, the rotation frequency of the external magnetic field was too high when the rotation frequency of the microrobot reached 24 Hz; the rotation frequency of the permanent magnet inside the microrobot could not be consistent with the external magnetic field, and the microrobot reached the cut-off state and could not continue to move [27,28]. Therefore, when the rotational frequency was greater than 24 Hz, this was the cut-off area of the targeted drug delivery microrobot.…”

Polishing of Silicon Nitride Ceramic Balls by Clustered Magnetorheological Finish

“…In contrast, relatively large areas of the spherical surface were enveloped by the tool trace of eccentric V-groove finish (Figure 8b). This is because the eccentricity of the two abrasive plates increased the range of the rotating angels θ and ϕ, which subsequently increased the area of envelopment by the tool trace [29,30]. As for CMRF method, the range of the rotating angel is larger than that of eccentric V-groove finish due to the combination of the plates eccentricity and the flexible of the contact between the ball surface and magnetorheological pads, which is in turn readily to form a fully-enveloped tool trace on the spherical surface [31].…”

Performance Evaluation of a Magnetically Actuated Capsule Microrobotic System for Medical Applications

“…We measured the magnetic field in the region of interest of the Helmholtz coils using our proposed measurement system [32]. The Gauss meter (TM701, KANETEC, Nagano, Japan) was used to measure the magnetic field between each Helmholtz coil, as shown in Figure 7a.…”

“…Meanwhile, the microrobot rotates synchronously with the changing frequency of rotational magnetic field, due to a pure magnetic moment is generated as a dipole of magnet attempts to align with the local magnetic field. The magnetic force and magnetic torque is defined by Equations (12) and (13) [32]. T=VM×B F=Vfalse(M⋅∇false)B where, V and M represent the volume and average magnetization of the magnetically microrobot, respectively.…”