The development of an accurate drug delivery system (DDS) is essential for the next generation of capsule endoscopy. Such a system would allow clinicians to treat diseases in the gastrointestinal tract in a non-invasive way. A variety of external magnetic systems have been proposed to articulate on-board magnets and enhance capabilities of prototype capsule robots. However, longer operating distances and further miniaturization of the on-board magnets are still needed in such prototypes. In this paper, we propose a novel magnetic system that consists of an array of arc-shaped magnets, which activates a drug-delivery system, based on an overly miniaturized slider-crank mechanism. The source for the magnetic field is optimized by means of analytical models. Our experimental results show that an optimal configuration enhances the magnetic field, magnetic torque and subsequently, a higher force is generated on the piston of the drug delivery system that expels drug out of a reservoir.