A new minuscule robot brings targeted delivery of medication to specific locations in the human body one step closer. Thanks to its design, the robot can move efficiently through the human body. Due to the presence of diverse structures of tissues and body fluids, the human body is a challenging environment for robots that contains all kinds of obstacles.
Medication is currently not delivered in a targeted manner, requiring it to travel through the human body to reach its target. This method has significant drawbacks. For instance, medication not only reaches its intended location, but can also affect healthy tissue. Robots enable more targeted delivery of medication. By transporting medication with tiny robots inside the human body to the desired location, medication can be administered much more accurately and such negative side effects avoided.
Difficult conditions for robots
However, moving a robot through the human body is not easy, partly because conditions inside the human body complicate the robot's journey. For example, inside the body, the robot encounters surfaces covered in body fluids such as blood or mucus, making it difficult for the robot to get a grip. In addition, the robot has to travel through spaces filled with such fluids and, again, manage to move around efficiently.
"The rough surface and varying texture of different types of tissues in the human body make transport challenging. Our multi-legged robot shows impressive performance in diverse terrains and enables a wide range of applications to deliver medication into the human body," explained Professor Wang Zuankai of the Department of Mechanical Engineering (MNE) at City University of Hong Kong (CityU).
Hundreds of tiny legs
A research team led by CityU has developed a robot that can handle such conditions well, bringing the use of such robots closer. The robot is equipped with hundreds of tiny legs less than 1 mm long, which enable it to move efficiently through the human body.
The robot is inspired by nature, reports the university. The researchers analysed hundreds of land animals, focusing on their legs. "Most animals have a ratio of 2:1 to 1:1 between the length of their legs and the distance between them. We therefore decided to give our robot a 1:1 ratio," explained Dr Shen Yajing, a professor in the Department of Biomedical Engineering at CityU. The research team was led by Yajing.
Minimal friction
The tiny robot has a body just 0.15 mm thick. Its legs are each 0.65 mm long, while the distance between them is 0.6 mm. These legs are pointed to minimise their contact area and thus the friction created when the robot crawls through the human body. Based on testing in laboratories, the researchers report that their robot produces 40 times less friction than a robot without legs under both dry and wet conditions.
These tests also show that the robot is capable of climbing obstacles 10 times higher than the length of its legs. In doing so, the robot lifts part of its body and places it at an angle of up to 90 degrees to be able to place its legs on the obstacle and climb over it. During this journey, the robot is capable of carrying a load as much as 100 times heavier than itself, making it comparable to an ant in terms of strength. By comparison, this is equivalent to a human lifting a minibus with room for 26 passengers.
Polydimethylsiloxane with magnetic particles
The robot is made of a silicone material called polydimethylsiloxane. This is a common polymer that incorporates silicon. In this material, the researchers have integrated magnetic particles, which allow the robot to be controlled by a magnet from outside the body and guided to the desired location. The speed at which the robot moves can be adjusted by changing the electromagnetic frequency.
"Both the material and the multi-legged design significantly improve the hydrophobic properties of the robot. In addition, the rubber material is soft and can be easily cut to give robot of all shapes and sizes for different applications," said Wang.
Moving forward in two ways
Once inside the body, the robot can move in two ways. In the first method, the robot only moves its legs at the front of its body, pulling itself forward, so to speak. In the second method, the robot "walks" by moving its right and left legs alternately from each other. The latter method is somewhat similar to the way humans walk, with one foot placed in front of the other each time.
The research team plans to further develop the robot in the near future. Central to this is:
- finding a suitable biodegradable material;
- studying new forms the robot can be given;
- introducing additional features.
After the robot is further developed, the team plans to test the robot on animals and eventually humans. "We hope in the next two to three years to develop a biodegradable robot that will naturally degrade once it has delivered its medication," Shen explains.
Many similarities to German robot
CityU's robot, incidentally, is very similar to one presented earlier this year by Germany's Max Planck Institute for Intelligent Systems. This minuscule robot can also deliver medication into the human body in a targeted manner. Like CityU's robot, it can be controlled by a magnet thanks to magnetic particles embedded in the robot's body.
There are more similarities. For example, the German institute's robot is also capable of navigating over uneven terrain and through bodily fluids. Like CityU's robot, the Max Planck Institute's robot is additionally largely inspired by nature. The German researchers looked at how larvae of beetles, caterpillars and jellyfish propel themselves.
The Max Planck Institute's robot was tested in an artificial surgical model of the human stomach and the tissue of a chicken. In both cases, the research team managed to guide the robot to the desired destination by steering it using magnetic fields. More information about this robot can be found here.
Author: Wouter Hoeffnagel
Source: City University of Hong Kong (pictured)
Source: EurekAlert!
Source: Max Planck Institute for Intelligent Systems
