To establish a reliable, reproducible and accurate release of the drug in the gastrointestinal tract, a novel release mechanism for a controllable drug-delivery system has been investigated. The release mechanism, consisting of a one-way valve for drug release, a drug chamber, two axially magnetized cylindrical permanent magnets and a multi-layer solenoid coil, is hosted in the capsule-shaped shell with diameter 11 mm and length 30 mm. To actuate the coil piston, the two static magnetic fields produced by the two magnets are aligned along the same axis, having the same magnitude, but opposite directions. Based on the principle of the electromagnetic force and the Bernoulli equation, the actuating force can be expressed as a function of the coil stroke and the excitation current, which was modeled and experimentally verified. Thus the actuating force can be controlled by adjusting the activated period and intensity of the coil, resulting in the reproducible release with different doses and mean rates. Then, a prototype of the drug-delivery system has been developed, which consists of a drug-delivery capsule, a radio frequency transmission module, an interface circuit, and an instruction setting and triggering platform. All the drug release parameters, including the release mode, times, dose and mean flow rate, can be set by the platform. The experiment verifies that the drug-delivery capsule can deliver a predetermined dose with different flow rates and dip angles of the capsule. The relative error of the releasing dose becomes larger with increasing releasing rate and decreasing releasing dose.
