4D-printed shapeshifters show potential for biomedical implants

Researchers from Rice University (TX, USA) have developed a 4D printing method to produce objects capable of changing shape in response to temperature changes, electric current or stress.

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Researchers from Rice University (TX, USA) have developed a 4D printing method to produce objects capable of ‘shapshifting’ in response to temperature changes, electric current or stress.

Described in ACS Applied Materials and Interfaces, the technique is referred to as ‘reactive 4D printing’ and is reported to have potential applications in biomedical implants. Having originally reported the ability to develop morphing structures, the team has now overcome a major limitation, decoupling the printing process from shaping.

Rafael Verduzco, Associate Professor in the Department of Chemical and Biomolecular Engineering at Rice University, explained:

These materials, once fabricated, will change shape autonomously. We needed a method to control and define this shape change. Our simple idea was to use multiple reactions in sequence to print the material and then dictate how it would change shape. Rather than trying to do this all in one step, our approach gives more flexibility in controlling the initial and final shapes and also allows us to print complex structures."


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The main challenge for the team was to create a printable liquid crystal polymer, incorporating mutually exclusive sets of inter-molecule chemical links. One set would provide integrity to the original printed shape, whereas the other set would be capable of physically manipulated after the printing process. The links are then ‘locked in’ by curing the alternate form under UV light.

When the two different forms have set, the material is capable of transforming between the two forms in response to a stimulus, for example, when heat is applied or when the object is cooled.

There were a lot of parameters we had to optimize - from the solvents and catalyst used, to degree of swelling and ink formula - to allow the ink to solidify rapidly enough to print while not inhibiting the desired final shape actuation," Graduate Student, Morgan Barnes (Rice University) explained.

Future work will further optimize the printing formula and use scaffold-assisted printing techniques to create actuators that transition between two different complex shapes. This opens the door to printing soft robotics that could swim like a jellyfish, jump like a cricket or transport liquids like the heart," Barnes concluded.

Source: Barnes M, Sajadi S, Parekh S, Rahman MM, Ajayan PM, Verduzco R. Reactive 3D printing of shape programmable liquid crystal elastomer actuators. ACS Appl. Mater. Interfaces. doi: 10.1021/acsami.0c07331 (2020) (Epub ahead of print); https://news.rice.edu/2020/06/09/lab-makes-4d-printing-more-practical/


Lead image: Shapeshifting materials produced at Rice University (TX, USA) with a 3D printer morph from their original form to an alternate through changes in temperature, electric current or stress. This example shows how one printed configuration can be programmed to take various shapes. Credit: Verduzco Laboratory/Rice University

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