This is how 4D printing can be briefly described, where time is an additional dimension. Recently, scientists led by Eva Blasko from the University of Heidelberg presented a new technique that enables the printing of complex structures on a microscale. Later, they can be significantly increased – up to eight times the original size. However, this is not the end, because it is also about harder or softer.
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An important role in the whole process is played by the ink, consisting of dynamic chemical bonds that can be closed or opened, which allows you to adjust the mechanical properties of the printed object or introduce new material. Blasco’s team used so-called two-photon laser printing, which uses a laser beam to illuminate ink that reacts chemically when exposed to light. This usually leads to a polymerization phenomenon.
4D printing uses time as an extra dimension
By focusing the laser beam on a spot, you can create a network of polymers that is used in precision 3D printing. The authors of a new study on the matter improved this approach a bit: they created a different ink formula in which the polymer has a special type of chemical bond known as a dynamic covalent bond.
The publication, dedicated to the achievements of the researchers, found a place in the headlines Advanced functional materials. Blasko and her colleagues have 3D printed microscale models of a flower, an octopus and a gecko. Their diameters were counted in micrometers, and as a result of polymerization, these objects took the form of rubber. They were then immersed in a vial containing styrene, which when heated triggers the opening of dynamic covalent bonds. Under these circumstances, polystyrene strips are formed between the two ends, resulting in an eightfold increase in the volume of the models in approximately four hours. The addition of polystyrene hardens the models, which retain their original shape and detail.
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It is even possible to change the mechanical properties of printed structures without changing their size. It was enough to heat them in the presence of a molecule to help open the dynamic bonds. As a result, the objects became softer. As Blasko summarizes, her team’s achievements are far from practical, but they show how enormous the potential of this technology is. According to the researcher, incorporating dynamic covalent chemistry into 3D printing will provide unique opportunities. It is even possible to create monomers with new functionality such as flexibility or fluorescence.