Shape-Programmable Soft Capsule Robots for Semi-Implantable Drug Delivery

In this paper, we present a shape-programmable magnetically actuated soft capsule robot for semi-implantable drug delivery applications. The shape of the proposed soft capsule is changed by an external magnetic field. To change the robot shape by an external permanent magnet, the relevant soft robot design features and required conditions are investigated using simulations and experiments. If the magnetic field is increased above a critical value, the capsule collapses to a sphere-like stable shape, which keeps the capsule inside the stomach all the time, and it cannot move to the duodenum by gastric peristalsis. We conducted experiments inside a synthetic stomach-like membrane to investigate how much tissue stress is induced by the soft capsule under emulated gastric peristalsis to show that the capsule induces no pain in the stomach and can sustain its spherical shape against external forces. Such a soft capsule can be used to release drugs, which can be contained on its body parts or inside a reservoir, while staying in the stomach. After depletion of the drug, a controlled rolling motion using the external magnetic field is proposed to recover the initial cylindrical shape. Then, the capsule can move into the duodenum by peristalsis and is discharged through the anus.