A Dartmouth College study has shown how heat can be used to create 3D printable gels with a variety of functional properties.
Describing the new process as ‘kinetic trapping’, the scientists point out to how molecular stoppers – or speed bumps – regulate the number of rings going onto a polymer chain and also control ring distributions. When the rings are bunched up, they store kinetic energy that can be released, much like when a compressed spring is released.
What Dartmouth assistant professor Chenfeng Ke and his team have done is use heat to change the distribution of rings and then moisture to activate different shapes of the printed object.
According to Ke, printing objects with different mechanical strengths using a single ink could replace the costly and time-consuming need to use several inks to print items with multiple properties.
“It’s a process that could make the 3D printing of complex objects easier and less expensive,” says Ke.
To demonstrate the efficacy of their process, the scientists used their newly developed 3D ink to print a flower which closes when exposed to moisture.
Different parts of the printed flower have different levels of flexibility created by the arrangement of molecular rings.
The mixture of properties allows the soft petals to close while the firmer parts of the flower provide structure.
Printing the same flower using current 3D printing methods would have meant combining different printed materials to get the desired effect.
“The different parts of this object come from the same printing ink,” explains Ke. “They have similar chemical compositions but different numbers of molecular rings and distributions.”
“These differences give the product drastically different mechanical strengths and cause them to respond to moisture differently.”
Refining the molecule even further could allow the scientists to print ‘fast-responsive actuators’ and soft robots using sustainable energy sources, such as variation in humidity.
The resulting printed objects could then be used for medical devices or in industrial processes, says Ke.
Image and content: Ke Functional Research Group/Dartmouth College