Researchers at Virginia Tech have developed a process for 3D printing latex rubber in collaboration with Michelin North America.
In a journal article published inside ACS Applied Materials & Interfaces, the researchers have detailed their initial findings in endeavouring to 3D print with this historically challenging material, including chemically modifying liquid latexes to make them printable and building a custom 3D printer.
The joint industry-academic discovery was made as a result of the National Science Foundation award aligned with the Grant Opportunities for Academic Liaison with Industry program. While attempts to 3D print with latex rubber have already been made and documented in scientific literature, this latest research from the Macromolecules Innovation Institute (MII), the College of Science, and the College of Engineering is said to come closer to replicating the mechanical properties of the material in additive manufacturing than ever before.
After initially attempting to manufacture a material that would provide the ideal molecular weight and mechanical properties, the researchers turned to commercial liquid latexes. These materials are extremely fragile and difficult to alter, which would be necessary to enable printing in a solid state. The team came up with a lattice structure that would hold the latex particles in place and allow for photoinitiators and other compounds to be added to facilitate 3D printing under UV light.
To do this, a custom 3D printer was built based on a patent filed in 2017 by two members of the team involving scanning UV light across a large area. The printer recoats a thin layer of latex resin and a projector then cures a specific area of the build area with UV light. The first version led to some fluid latex particle scattering outside of the projected UV light on the latex resin surface, resulting in inaccurate parts. However, for the second version, they embedded a camera to examine how the light reacts with the material and adjust print parameters accordingly to ensure curing of just the intended shape.
The final 3D printed latex parts exhibited strong mechanical properties in a matrix known as a semi-interpenetrating polymer network, which was the first time this had been documented for elastomeric latexes. The hope is that this initial research will open up the ability the print with a variety of elastic materials for applications such as soft robotics and medical devices.
The full report, authored by Philip J. Scott, Viswanath Meenakshisundaram, Maruti Hegde, Christopher R. Kasprzak, Christopher R. Winkler, Keyton D. Feller, Christopher B. Williams, and Timothy E. Long, can be accessed here.