Theoretical analysis and simulations of micro-dosing locomotive robot with drug-release mechanism

• By taking advantage of magnetic poles, the micro-wheel is able to roll rapidly.
• Two cascaded strategies based on sliding mode control are developed and verified.
• The phenomenon of jerk can be suppressed by the dual sliding mode controllers.

A micro-dosing system model of overall size 5×5×4.2 mm3 for drug delivery is proposed and presented. The drug delivery system mainly consists of a micro-wheel and a micro-drug release mechanism. The motion of the micro-wheel is controlled by changing the gravity center of a running disk, which is placed within the hollow micro-wheel and attracted by the actuated micro-solenoids fabricated on the inner wall of micro-wheel in shift. In addition, the micro-wheel is controlled to roll forwards/backwards to the designated location by two sliding mode control strategies: one for long-distance motion (to transport the drug to the vicinity of the spots under disease) and the other for short-distance motion (to decelerate down and stop at the exact drug-release location). On the other hand, the micro-drug release mechanism is composed by a cantilever beam and a chamber filled up by medicine. The pyramid tip of the cantilever beam deflected by the applied electrostatic force is designed to penetrate the micro-film which seals the chamber so that the medicine can be released at the specified spot. The so called “pyramid tip” is, in fact, to replace the conventional medical needle. Its profile is like a pyramid to comply with the MEMS (Micro Electro Mechanical System) fabrication process. This “pyramid” is constructed at the free end of a cantilever beam and hence named as a “pyramid tip”.