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A research team at City University of Hong Kong (CityU) has successfully developed the world's first-ever 4D printing of ceramics. In a paper published this August in the journal Science Advances, the CityU team describe how robust and complex shapes can be made with proper heat treatment of the novel "ceramic ink”, which is likely to have a profound impact on future possibility for the structural applications of ceramics.
Overcoming the Temperature Limitations of 3D Printed Ceramics
Ceramics offer a huge potential to a number of industries. They can be used in spaceflight and aviation due to their low weight in comparison to alternative materials, they can be used as cutting tools, refractory materials, thermal insulators, electrical insulators, and more. In addition, ceramic material is currently the only 3D printing material that has been determined to be food safe. Therefore, it is the only material that can be used to create safe, non-toxic 3D printed kitchen and tableware.
However, the field of printed ceramics has been prevented from reaching its full potential due to a major limitation. Because of their excellent thermal properties, ceramics have high melting points, which poses a challenge to 3D printing as the required high temperatures make it difficult to use the conventional laser printing processes established for other materials. Currently established methods of ceramic 3D printing are limited in their abilities to create complex shapes because of the limitations posed by these high temperatures.
In overcoming this limitation, the applications of ceramics could grow, which would benefit numerous industries.
The Development of Elastic Precursors Leading to 4D Technology
Led by Professor Jian Lu, Vice-President (Research and Technology) and Chair Professor of Mechanical Engineering at CityU, the team of researchers set about overcoming the challenges of 3D printing ceramics by developing a ceramic ink out of a combination of polymers and ceramic nanoparticles.
The team established an ink that can create 3D-printed ceramic precursors that are soft and can be stretched to more than three times their original length. These malleable precursors allow for the creation of complex shapes, and even origami folding. Following proper heat treatment, complex-shaped ceramics can be produced.
The establishment of these elastic precursors led to further breakthroughs in the development of two methods of 4D printing of ceramics.
Integrating the element of time into 3D printing is what gives it its fourth dimension. 4D printed objects have the capability of re-shaping and/or reassembling themselves over time following the influence of an external stimulus, such as a magnetic field, temperature change, or a mechanical force. The elastic energy that was stored in the stretched precursors was used for shape morphing. The release of the stretched precursors following heat treatment led to self-reaping, turning the precursors into ceramics.
The research demonstrated that the ceramics created by these elastomers proved to be mechanically robust, with a high compressive strength-to-density ratio (547 MPa on 1.6 g cm-3 microlattice). In addition, they found that they could be created in much larger sizes than traditional 3D printed ceramics can achieve.
The process of creating this method took over two and a half years, but the result was that the limitations of 3D printed ceramics were overcome, and a system of 4D ceramic printing was developed.
The Future for Printed Ceramics
The lead researcher, Professor Lu, believes that what the team has accomplished in creating printed ceramic precursors with versatile shape-morphing properties will radically change many industries.
Particularly, electronic devices are likely to benefit from this development, given that ceramic materials perform better at transmitting electromagnetic signals than their metallic material counterparts, the advent of printed ceramic components in electronics could enhance the capabilities of electronic devices. What’s more, ceramic products are predicted to play a vital role in the production of electronic devices following the arrival of 5G networks.
In addition, the potential to create complex shapes with printed ceramics is predicted to allow for the development of tailor-made products, such as uniquely designed ceramic mobile phone backplates.
Finally, the aviation and space industries are likely to be impacted by this innovation as ceramic materials are lighter than traditional materials while often matching their strength and robustness. The future of aerospace production will likely incorporate 4D ceramic printing methods.
Sources and Further Reading
- Chen, Z., Li, Z., Li, J., Liu, C., Lao, C., Fu, Y., Liu, C., Li, Y., Wang, P. and He, Y. (2019). 3D printing of ceramics: A review. Journal of the European Ceramic Society, 39(4), pp.661-687. https://app.dimensions.ai/details/publication/pub.1108035773?and_facet_source_title=jour.1136517
- Liu, G., Zhao, Y., Wu, G. and Lu, J. (2018). Origami and 4D printing of elastomer-derived ceramic structures. Science Advances, 4(8), p.eaat0641. https://advances.sciencemag.org/content/4/8/eaat0641/tab-article-info