Mechatronic refilling device for long-term implantable artificial organs

Objective: this work introduces a new paradigm for a lifelong-implanted completely automated artificial pancreas (AP) refilled by swallowable pills. We report data about the design and development of an implanted docking system and a refilling mechanism to be interfaced with the gastrointestinal tract, thus allowing long-term maintenance of a chronically implanted mechatronic AP. Methods: the implanted docking system is based on a miniaturized Magnetic Switchable Device (MSD). Finite element method (FEM) analyses allowed to identify the most appropriate MSD design features and precision machining permitted its fabrication. A rotary DC motor assures MSD activation/deactivation. The swallowable capsule, carrying insulin and fabricated in polydimethilsiloxane, is provided with an RFID tag for its detection by the implanted system and with a ferromagnetic ring for docking. The refilling system is based on a miniaturized linear motor which pushes a needle into the duodenum/stomach internal lumen, in order to punch the docked capsule and to transfer the insulin from the capsule to the internal reservoir, thanks to a miniature pump. A dedicated passive valve integrated in the implantable system is the interface between the device and the body, thus allowing capsule punching and automatically closing after needle retraction. Results: FEM analyses permitted to identify the best MSD shape which maximizes the contact area with the docked capsule. A Ni-Co-Fe alloy and an N52 NdFeB magnet were employed for achieving an attraction force of 11 N in the “ON” configuration and 1.41e-5 N in the “OFF” configuration. In addition, for a passive valve of 10 x 10 x 2.5 mm3, the maximum opening is ~ 1 mm, thus allowing the use of a 31G insulin needle. Conclusion: The developed prototype requires further miniaturization, but it demonstrates the feasibility of a mechatronic implantable device for non invasive refilling of artificial organs based on swallowed cargos.