Materials that are capable of changing their properties in response to variation in the environment hold a promise for all sorts of applications. An international team comprised of scientists has managed to develop new and quite innovative material, light-stabilized dynamic material, that has the capability of becoming stiff under a certain kind of light and becoming soft in the dark. This new material may very well find its application in 3D printing; it could be used as support that could melt away once the job is done.
The creators of light-stabilized dynamic material belong to Australia’s Queensland University of Technology (QUT), Belgium’s Ghent University and Germany’s Karlsruhe Institute of Technology, and comprises of a polymer structure that is capable of altering its structure in light, and then reverting back. What allows this to happen? The answer lies in the inexpensive chemical compounds that the team has incorporated into the material. These compounds include the coupling molecules known as thiazolidinediones and naphthalene (a common ingredient found in moth repellents).
On the whole, these allow the light-stabilized dynamic material to remain in solid form as long as it is being exposed to green LED light. However, as soon as the light is switched off and the material is allowed to stay in the dark for some time; the chemical bonds begin to cease, and thus the material becomes a soft and runny mess. When you switch the light back on, the material hardens up again. The team dimmed the light instead of shutting it off and was able to tweak the mechanical properties between the two extremes.
The researchers say, ‘Typically, you use different wavelengths of light or additional heat or harsh chemicals to break up the polymer molecule chains that form a network structure. However, in this case, we used a green LED light to stabilize the network. The trigger to break up the network, make it collapse and flow away is actually the mildest one of all: darkness. Switch the light back on and the material re-hardens and retains its strength and stability.’
The team is hopeful that light-stabilized dynamic material will pave the way for a new class of materials that can respond to light in unique and beneficial ways. Professor Christopher Barner-Kowollik, a macromolecular chemist at QUT, said, ‘What you need to 3D print something like a bridge is a support scaffold, a second ink that provides that scaffold during the printing of the design, but which you can later remove when it is no longer needed. With a light-stabilized dynamic ink used as a scaffold, you could 3D print under light, then switch the light off to let the scaffold ink flow away.’
The research has been published in the Journal of the American Chemical Society.