Researchers at City University Hong Kong (City U) have just created a tiny, soft robot with caterpillar-like legs that can be directed using magnets to deliver drugs around the body. The robot can carry a therapeutic payload of more than 100 times its own weight and has been specifically designed to be able to carry drugs to areas like the stomach.

When an external magnetic field is applied, the soft body of the robot will locate in a magnetic field and experience both a torque and a force proportional to the strength of the magnetic field. The torque aligns the millirobot with the magnetisation field, raising the body. Meanwhile, the magnetic force provides a driving force and drags the millirobot towards the local maximum magnetic field. The robot deforms under the magnetic field, which is controlled precisely during the accurate permanent magnet motion. This allows the robot to move like a caterpillar in the body. 

The caterpillar design was chosen because legs and feet are commonly found in animals. Legs lift an animal’s body from the ground, which leads to a decreased amount of body friction on the ground, higher degrees of freedom in locomotion, reduced energy cost, and enhanced obstacle crossing ability. These capabilities allow them to travel across complex terrain, which is a valuable quality for use in the human body.

The robot designed by researchers will be used as a prototype as the team works towards creating a fully biodegradable robot that will naturally decompose after drug delivery. The team are also redesigning the robot to be able to better navigate around the body, including the ability to detect and respond to lesions with target therapy.