A new kind of gel or ink may advance the development of personalised implants made of biomaterials. The gel liquefies as soon as it is pushed under pressure through the nozzle on the print head of a 3D printer. However, as soon as the material leaves the nozzle, the ink hardens again in a short time.
Several researchers worldwide are currently working on biomaterials for medical implants. A major limitation in this development is the need to develop a new ink for each application. "If someone wants to reproduce part of an eye, for example, they could not build on the work of people who have designed auricular prosthesis," explains Mark Tibbitt, professor of Macromolecular Sciences at Swiss university ETH Zurich.
Toothpaste problem
The major challenge in creating this gel is also described as the 'toothpaste problem'. Toothpaste should not be too solid, as this would make it too difficult to push the toothpaste through the opening of the tube. However, the paste should not be too liquid either, as otherwise it will drip right off the toothbrush.
A similar challenge exists in 3D printing. The gel used to print must be liquid enough to be pushed through the printer's nozzle. Then, the ink must cure quickly enough to prevent the printed object from losing its shape.
Combination of cellulose fibres and nanoparticles
The new ink developed by Tibbitt's team offers a solution. The gel consists of cellulose fibres dissolved in water, combined with biodegradable polymeric nanoparticles. If no pressure is applied, the fibres automatically adhere to the particles. The resulting structure breaks if pressure is applied by the nozzle, which liquefies the material. Once this pressure disappears, the material hardens again in a short time.
The researchers report that the ink appears to have no impact on living cells; during tests, as many cells were found to survive inside the gel as outside it. By adding hydrophobic substances to the nanoparticles, the researchers also expect to be able to use their new gel to deliver medication into the human body.
Author: Wouter Hoeffnagel
