Design and operation principles of the magnetically driven pump (MDP). (A) 3D schematic images of the constituent units. (B) Optical image of the MDP. The scale bar is 1 cm. (C) Schematic description of the MDP operation. ① The electromagnet is placed above the implanted MDP; ② a positive voltage is applied, and the polarity of the electromagnet attracts the Mp; ③ the plunger moves upward, and ④ the insulin solution in the drug reservoir is aspirated into the barrel; ⑤ a negative voltage is applied, and the polarity of the electromagnet repels the Mp; ⑥ the plunger moves downward, and ⑦ the insulin is infused through the check valve.