Tiny Robots Propel Through Human Eyeball to Deliver Drugs

A team of international scientists has developed propeller-shaped nanorobots that are able to drill through dense tissue like in the eyeball for the first time. Researchers of the Micro, Nano and Molecular Systems Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, teamed up with collaborators from around the world to develop the groundbreaking technology.

The tiny nanopropellers are just 500 nm wide, the right size to fit through the tight molecular matrix of the gel-like substance in the vitreous. Covered in a non-stick coating these drills are 200 times smaller than the diameter of a human hair, even smaller than a bacterium´s width.

The slippery coating allows robots to slip through tough tissue

Their tiny size, in combination with their slippering exterior, allows them to move through the eye without damaging the sensitive biological tissue around them. This is the first time that scientists have managed to physically steer nanorobots through very dense tissue.

Previously the idea had only been demonstrated in models or in biological fluids. It is hoped that in the future the robots will be able to very accurately deliver drugs and other therapeutic agents to targeted areas of the body.

Targeted drug delivery key 

Delivering medicine to target areas is currently very difficult to do, particularly in areas of dense tissue and at small scales. The eye also poses a unique set of challenges. The eyeball is made of a very dense material with a tight matrix, that the nanopropellers must squeeze through.

The eyeball also has a very specific biopolymeric network that prevents objects from passing through them, making it difficult even for the tiny robots not to get entangled. The scientists use the analogy of a tiny corkscrew trying to make its way through a web of double-sided adhesive tape as a tool to imagine the difficulty of the task.

Finally, once, the movement is possible, precise movement poses another set of problems. To overcome these scientists add a magnetic material, like iron, so that they can be steered to their destination using magnetic fields.

Scientists inspired by nature

The first layer of slippery coating applied to the nanorobots consists of molecules bound to the surface, while the second is a coating with liquid fluorocarbon. This clever combination allows the nanorobots to slip through the tight mesh of the eyeballs dense tissue.

“For the coating, we look to nature for inspiration”, the first author of the study Zhiguang Wu explains. He was a Humboldt Research Fellow at the MPI-IS and is now a postdoc at the California Institute of Technology. “In the second step, we applied a liquid layer found on the carnivorous pitcher plant, which has a slippery surface on the peristome to catch insects. It is like the Teflon coating of a frying pan.

This slippery coating is crucial for the efficient propulsion of our robots inside the eye, as it minimizes the adhesion between the biological protein network in the vitreous and the surface of our nanorobots.”

The incredible research can be read in the article “A swarm of slippery micro-propellers penetrates the vitreous body of the eye”, by Zhiguang Wu, Jonas Troll, Hyeon-Ho Jeong, Qiang Wei, Marius Stang, Focke Ziemssen, Zegao Wang, Mingdong Dong, Sven Schnichels, Tian Qiu, Peer Fischer, published in Science Advances (2018).