4D printing? Yes! 4D printing is a process through which a 3D printed object transforms itself into another structure over the influence of external energy input as temperature, light or other environmental stimuli.
The new process was developed by Dartmouth College’s Ke Functional Materials Group together with Kohzo Ito which focuses on developing smart materials for 3D and 4D printing applications. They describe Kinetic Trapping as a process that uses heat to change the arrangement of a cyclodextrin and PEG-based polypseudorotaxane.
The molecules used in the process create an ink that alters the distribution of cyclodextrins over time, and change the material from a powder into a 3D printable gel. Moisture is then used to activate different shapes within the 3D printed object.
The researchers accessed the energy-holding “meta-stable” states of these structures transforming the 3D printed objects into actuators that change their shape in response to moisture.
To demonstrate their research, the team 3D printed a flower using an ink produced by the technology. Different parts of the flower were found to have different levels of flexibility due to the variable arrangement of molecular rings. The mixture of properties subsequently created allowed the soft “petals” of the flower to close when they were exposed to moisture, while the firmer parts of the flower provided structure.
The paper of the group (Lin et al., Chem. 7,1–18, September 9, 2021) is now openly accessible from here: https://www.sciencedirect.com/science/article/pii/S2451929421003089?dgcid=author
The authors also shared a fascinating video on the 4D properties of the printed flower-shaped object.