Ordinarily, if you want to make a 3D-printed liquid-filled object, you have to inject the liquid after the object has been printed. A new process, however, allows such items to be printed all in one step – and the technology could have some valuable applications.
The technique was developed by a team at Germany's Martin Luther University Halle-Wittenberg, led by Prof. Wolfgang Binder and researcher Harald Rupp. It utilizes a unique system that incorporates two 3D printing heads – one builds objects up by extruding successive layers of molten polymer, while the other (an inkjet print head) deposits tiny droplets of liquid.
The process begins with the extruder head being used to print a solid polymer base, on top of which it prints a waffle-like lattice grid made of criss-crossing polymer strands. Next, the inkjet head deposits droplets of liquid into each of the gaps within that grid. The extruder head then gets back into action, printing a solid cap over top of the grid, sealing the liquid inside.
In one demonstration of how the technology could be used, the scientists printed capsules that were made of a biodegradable polymer and filled with an "active liquid substance." Even after being subjected to the heat of the printing process, the liquid retained its active qualities – this suggests that the system could be utilized to manufacture capsules that slowly release medication within the body.
In another demonstration, a luminous liquid was sealed inside a plastic material. When that material was subsequently stressed to the breaking point, the liquid leaked out, clearly indicating that damage had occurred. Such material could ultimately be built into key areas of aircraft or automobiles, providing authorities with a warning that those areas may be under too much mechanical stress.
It is hoped that once developed further, the 3D printing technique could also be used to create self-healing materials or even battery components.
"The future lies in more complex methods that combine several production steps," says Prof. Binder. "That is why we were looking for a way to integrate liquids directly into the material during the printing process."
The research is described in a paper that was recently published in the journal Advanced Materials Technologies.
