Shape memory alloy clamping devices of a capsule for monitoring tasks in the gastrointestinal tract

This paper describes the development of an active clamping mechanism to be integrated into a swallowable pill for the diagnosis of the gastrointestinal (GI) tract. The clamping system allows us to stop the pill at desired sites of the GI tract for long monitoring purposes. After discussing the major technical constraints, the design of the core component, i.e. the gripper, based on FEA (finite element analysis), is illustrated as well as its fabrication process. Symmetric and asymmetric gripper designs are described. The actuation is provided by shape memory alloys (SMA), and it is driven by a dedicated electrical interface. Then the working prototypes have been tested in vitro: for both kinds of grippers a pull-back force up to 0.6 N has been measured. A preliminary theoretical model for the gripper has been derived and compared to the experimental results.