Swallowed the battery? Have a bite with the robot!

In experiments on a model of the human esophagus and stomach, researchers at the Massachusetts Institute of Technology, working under the guidance of Professor Daniela Rus, together with colleagues from the University of Sheffield and the Tokyo Institute of Technology, demonstrated the ability of a tiny origami robot to be released from a swallowed capsule, move under the influence of external magnetic fields along the stomach wall and remove the battery stuck to it tablet type.

The new robot is not unique in its kind, but it differs significantly from its predecessors. Like the previous development of the authors, it can move forward according to the principle of "intermittent sliding", which consists in the fact that its protruding parts are attached to the surface during movement due to friction forces, after which they are released again when the robot body bends to change its weight distribution.

Just like a number of its predecessors, the new robot consists of two layers of structural material, between which there is a material that shrinks when heated. The complex of notches on its outer layer determines the nature of the robot's bending when the middle layer is reduced.

The intended use of the robot necessitated a number of structural modifications. Movement on the principle of intermittent sliding is possible only if the robot is inflexible and has rather small dimensions. Compared to its last predecessor, the new robot is more elastic, due to its manufacture from a biocompatible material. In order to compensate for this elasticity, the researchers developed a new robot design with fewer notches on the outer surface. At the same time, the folds of the robot's body increase its rigidity along certain axes.

In addition, it should be borne in mind that the stomach is filled with liquid and in such conditions, the robot's movement cannot completely occur on the principle of intermittent sliding. According to the authors, 20% of the forward movement is provided by fluid movement and 80% by intermittent sliding. With this in mind, the developers have provided the robot's body with a "fin".

By trial and error, the researchers came to the shape of the robot, which provides the possibility of its compression for placement in a capsule suitable for swallowing and subsequent self-restoration of the shape when it dissolves in the stomach. The resulting robot is a rectangle with concertina folds perpendicular to its long axis and with curved corners acting as adhesion zones with the stomach wall.

In the center of one of the folds there is a permanent magnet that reacts to changes in external magnetic fields that regulate the movement of the robot. The forces applied to the robot are predominantly rotational in nature. A fast rotation causes it to spin in place, and a slower rotation causes it to turn around one of its fixed "legs". During the experiments, the robot used the same magnet to remove the stuck battery.

In search of a structural material for the robot, the authors tested more than 10 different options until they settled on dried pork intestines used as a shell in the manufacture of sausages. To make the shrinking middle layer of the robot, they used a biodegradable compressible Biolefin shell.

The simulator used in the experiments was an open cross-section of the esophagus and stomach made of silicone rubber, filled with a mixture of water and lemon juice. This model was created in accordance with the mechanical parameters obtained during the study of a real pig organ.

Every year, 3,500 cases of swallowing batteries are recorded in the USA alone. Quite often they are excreted from the body naturally, but their prolonged contact with the esophagus or stomach tissue can lead to the appearance of an electric current, under the influence of which compounds are formed that damage the tissue. The authors hope that the origami robot they developed will allow not only to remove swallowed batteries from the esophagus or stomach without surgical intervention, but also to process the tissue damage remaining after them.

The results of the work will be presented at the International Conference on Robotics and Automation (International Conference on Robotics and Automation), which will be held on March 16-21 in Stockholm, Sweden.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the Massachusetts Institute of Technology: Ingestible origami robot.

18.05.2016