Magnetic control of self-propelled microjets under ultrasound image guidance

Abstract

This paper demonstrates closed-loop control of self-propelled microjets using feedback extracted from B-mode ultrasound images. Previous work on control of self-propelled microrobots has mainly employed video cameras equipped with microscopic lenses in order to obtain the required feedback. Nonetheless, in medical applications such as targeted drug delivery, the use of video cameras might be unsuitable for localizing microrobots that navigate within the human body. This issue is a major obstacle for transferring medical microrobotic technologies into the clinic. On that account, the first reported methods and results on control of self-propelled microjets using ultrasound equipment are provided herein. In order to exploit the microjets' self-propulsion mechanism, their motion is directed towards a predefined target by exerting magnetic torques to steer them. Binary image analysis techniques are used to estimate the microjet's position from the ultrasound images. Two air-cored coils are used to generate the steering torques within a plane. Coil currents are calculated using the estimated position error. Results show that our system employing ultrasound images allows control of microjets at an average velocity of 156±35.1 μm/s and with an average tracking error of 250.7±164.7 μm. As a reference, when microscopic image feedback is used in the setup, an average velocity and tracking error of 207±25.9 μm/s and 183.2±84.31 μm, respectively, are observed.

Evaluation of an electromagnetic system with haptic feedback for control of untethered, soft grippers affected by disturbances

“…This include the use of smaller scale grippers, the study of against-the-flow motion, and the use of clinically-compatible imaging, such as ultrasound, which is consistent with the ultrasound-visibility of the fabrication materials [14]. Moreover, we will test different types of haptic stimuli (e.g., vibratory, skin-stretch, pin-arrays) and sensory substitution techniques (e.g., visual, audio), with the objective of improving the results registered in this work.…”

“…Researchers have proposed a variety of motion control approaches for ferromagnetic agents using iron-core electromagnetic coils and feedback extracted either from a microscopic vision system [1], [13], or from B-mode ultrasound images [14]. Further, a deep knowledge of such systems and of their rejection to environmental disturbances is a fundamental requirement to reach the robustness and precision that medical procedures would require.…”

Control of untethered soft grippers for pick-and-place tasks

“…The B(P) of our setup has been evaluated in previous studies, using a finite elements model analysis, and successively verified using a calibrated three-axis Hall magnetometer [28]. The value of m mg is estimated in Sec.…”

A robust controller for micro-sized agents: The prescribed performance approach

“…For those microparticles, it is assumed that the buoyancy force is balanced by the surface tension force. The details of the image processing algorithm used to detect the center coordinates of the microparticles can be found in [25].…”