Abstract
Creating wireless milliscale robots that navigate inside soft tissues of the human body for medical applications has been a challenge because of the limited onboard propulsion and powering capacity at small scale. Here, we propose around 100 permanent magnet array–based remotely propelled millirobot system that enables a cylindrical magnetic millirobot to navigate in soft tissues via continuous penetration. By creating a strong magnetic force trap with magnetic gradients on the order of 7 T/m inside a soft tissue, the robot is attracted to the center of the array even without active control. By combining the array with a motion stage and a fluoroscopic x-ray imaging system, the magnetic robot followed complex paths in an ex vivo porcine brain with extreme curvatures in sub-millimeter precision. This system enables future wireless medical millirobots that can deliver drugs; perform biopsy, hyperthermia, and cauterization; and stimulate neurons with small incisions in body tissues.
Highlights
In the last decade, remarkable progress has been made to create small-scale medical robots that can operate inside the human body
We propose to solve this challenge by creating a robot actuation system with a stable magnetic force trap to drive a wireless milliscale magnetic robot inside soft tissues
We designed and fabricated a cylindrical magnetic millirobot that can move inside soft tissues actuated by the external magnetic forces
Summary
Remarkable progress has been made to create small-scale medical robots that can operate inside the human body. Many challenges arise from their small size, due to the difficulty to place onboard robotic components, such as actuators, sensors, power source, computation, communication, and control electronics, into the tiny robot body [1] With these limitations, two main approaches have been used in the literature: tethered macroscale robots with small-scale end-effectors and untethered (wireless) small-scale robots. Biohybrid microrobots have been proposed to enable cell-scale wireless robots by using the integrated live microorganisms as biological actuators, sensors, and taxis-based controllers [27,28,29] These small-scale robots have been demonstrated to navigate and operate inside body fluids and on body tissue surfaces; they have not shown the navigation inside body tissues due to the limited force and torque generated by the external actuation sources
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