New Method for Dynamic 3D Printing

The right material does the trick: The objects from the 3D printer are still movable even after printing and can be stimulated by a change of light or temperature. (Source: M. Hippler, KIT)

Laser-based 3D printing can already be used today to produce any structure on a micro­meter scale. However, for many appli­cations, especially in biomedicine, it would be advantageous if the printed objects were not rigid but switchable. Researchers at the Karlsruhe Institute of Tech­nology KIT have now been able to print micro­structures that change shape under the influence of temperature or light.

Direct laser writing is considered a parti­cularly promising method for 3D printing: A computer-controlled focused laser beam acts as a pen and creates the desired structure in the printer ink, which here is a photo­resist. In this way, any three-dimen­sional form down to a size of a few micro­meters can be created. ¬However, for many appli­cations, parti­cularly in biology and biomedicine, it would be desirable not only to produce rigid structures but also active systems that are still movable after the printing process, e.g., that can change their shapes by an external signal,” empha­­sizes Martin Bastmeyer from KIT’s Zoological Institute and Institute of Func­tional Interfaces.

In cooperation with Martin Wegener’s group at Institute of Applied Physics and Institute of Nano­technology at KIT as well as chemists from Karlsruhe and Heidelberg, a printing process for such movable structures has now been developed. Special materials, i.e., stimulus-respon­sive polymers whose properties can be modified by external signals, are used for the printer ink. The chemical compound poly(N-isopro­pysycraymide) changes its shape considerably when the temperature is raised only slightly above room temperature. The 3D structures produced in this way are functional in aqueous environments and thus ideal for appli­cations in biology and bio­medicine.

“We have developed the method to such an extent that we can also manu­facture complex structures in which, as a result of external stimu­lation, the moving parts do not all react in the same way, but show different but precisely defined reactions,” explains researcher Marc Hippler. This is made possible by grayscale litho­graphy, where the photo­resist is not exposed with the same intensity at all points, but is exposed in a graded manner. This allows the desired material properties, and thus the strength of the movement at a certain tempera­ture change, to be set very precisely. With computer simulations, the resulting movements can be precisely predicted and therefore allow a rational design of complex 3D structures.

The working groups around Martin Bastmeyer and Martin Wegener have gone one step further: Instead of tempera­ture, focused light is used as a control signal. For the first time, this allows the targeted control of indi­vidual micro­structures in a complex, three-dimen­sional arrange­ment. This feature could be used, for example, in micro­fluidic systems. Since the photoresist used can be switched at room tempera­ture, there are additional appli­cations in basic bio­logical research, e.g., the targeted mechanical mani­pulation of indi­vidual cells. (Source: KIT)

Reference: M. Hippler et al.: Controlling the shape of 3D microstructures by temperature and light, Nat. Commun. 10, 232 (2019); DOI: 10.1038/s41467-018-08175-w

Links: Institute of Functional Interfaces, Karlsruhe Institute of Technology KIT, Karlsruhe • Institute of Nanotechnology, Karlsruhe Institute of Technology KIT, Karlsruhe

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