The top panel is a 3-D printed plastic tab with the letters “UW” printed in a slightly different material. The bottom panel is the same material after stretching.
WASHINGTON, US: Imagine printing out molecules that can respond to their surroundings. A research project at the University of Washington merges custom chemistry and 3-D printing. Scientists created a bone-shaped plastic tab that turns purple under stretching, offering an easy way to record the force on an object.
“At the University of Washington, this is a marriage that’s been waiting to happen – 3-D printing from the engineering side, and functional materials from the chemistry side,” said Andrew J Boydston, Assistant Professor, University of Washington. He is corresponding author on a recent paper in the American Chemical Society’s journal of Applied Materials and Interfaces.
Gregory Peterson and Michael Larsen, University of Washington doctoral students in chemistry, created a polymer, or plastic made up of many repeated units strung together, and fed the soft plastic into the University of Washington chemistry lab’s commercial 3-D printer.
One print head contained polycaprolactone, similar to what a 3-D printer company sells as Flexible Filament. The other print head contained a plastic that is 99.5 per cent identical but the University of Washington team made occasional insertions of a molecule, spiropyran, that changes colour when it is stretched.
The printed tab is a piece of white plastic with barely visible stripes that turn purple under force. It acts as an inexpensive, mechanical sensor with no electronic parts. The whole device took about 15 minutes to print from materials that cost less than a dollar.
The sensor might be used to record force or strain on a building or other structure. Boydston would like to develop a sensor that also records the speed of the force, or impact, which could allow for a football helmet that changes colour when hit with sufficient force.
The project is part of a recent collaboration between Boydston’s group and co-authors Mark Ganter and Duane Storti, University of Washington mechanical engineers who have developed new 3-D printing materials and techniques.
Different instructions can programme the machine to print the plastics in any configuration – with the colour-changing part in stripes in the middle, completely encased in the other plastic, or in any other desired shape.
“It means making more complex molecules from simpler, more available ones. Maybe the material isn’t currently under stress, but it had been several times prior to your observing it. And so these types of materials could record that load history,” said Boydston.
Boydston will continue collaborating with Ganter and Storti, to plan and create more 3-D printed objects that incorporate designer molecules. The 3-D printing technology offers new possibilities, he said, for individualized medical implants or other custom shapes that incorporate engineered molecules that respond to their environment.
© University of Washington News