A capsule robot powered by wireless power transmission: Design of its receiving coil

• A hollow-cylinder like 3-D receiving coil which can wirelessly power a capsule robot is proposed.
• The proposed coil avoids increasing the length and improves the space utilization of the robot.
• A model has been proposed and verified effective in guiding the design of the coil.
• The effectiveness of the coil in capsule robot application has been validated in ex-vivo intestine.

Wireless power transmission based on near field inductive coupling is a promising solution to power a freely moving capsule robot for a long duration. Existing multi-dimensional receiving coils are normally solid cylinders, which increase the total length of the capsule robot. We propose using a hollow-cylinder like three-dimensional receiving coil to avoid increasing the length and to improve space utilization. This receiving coil consists of a circular coil, two pairs of planar coils, and a hollow-cylinder like ferrite core. Taking into consideration human safety and the limited available space in the capsule robot, the number of turns and the wire diameter of the receiving coil, as well as the transmission frequency, have been optimized. This receiving coil could output electric power ranging from 206 mW to 1130 mW; integrated to an inchworm-like capsule robot, it could successfully power the robot to travel through the ex-vivo intestinal tract and capture satisfactory intestinal videos for diagnosis.