World's first 4D printing for ceramics developed

Scientists have successfully developed the world's first 4D printing for ceramics, that can be used to create complex, shape-changing objects.

4D printing is conventional 3D printing combined with the additional element of time as the fourth dimension, where the printed objects can re-shape or self-assemble themselves over time with external stimuli, such as mechanical force, temperature, or a magnetic field.

Researchers from City University of Hong Kong (CityU) made use of the elastic energy stored in the stretched precursors for shape morphing. When the stretched ceramic precursors are released, they undergo self-reshaping. After heat treatment, the precursors turn into ceramics.

Ceramic has a high melting point, so it is difficult to use conventional laser printing to make ceramics.

The existing 3D-printed ceramic precursors, which are usually difficult to deform, also hinder the production of ceramics with complex shapes.

To overcome these challenges, researchers developed a novel "ceramic ink," which is a mixture of polymers and ceramic nanoparticles.

The 3D-printed ceramic precursors printed with this novel ink are soft and can be stretched three times beyond their initial length.

These flexible and stretchable ceramic precursors allow complex shapes, such as origami folding. With proper heat treatment, ceramics with complex shapes can be made.

The resultant elastomer-derived ceramics are mechanically robust. They can have a high compressive strength-to-density ratio, and they can come in large sizes with high strength compared to other printed ceramics.

"From making the ink to developing the printing system, we tried many times and different methods," said Lu Jian, a professor at CityU.

"Like squeezing icing on a cake, there are a lot of factors that can affect the outcome, ranging from the type of cream and the size of the nozzle, to the speed and force of squeezing, and the temperature," said Jian.

It took over two and a half years for the team to overcome the limitations of the existing materials and to develop the whole 4D ceramic printing system.

In the first shaping method, a 3D-printed ceramic precursor and substrate were first printed with the novel ink.

The substrate was stretched using a biaxial stretching device, and joints for connecting the precursor were printed on it. The precursor was then placed on the stretched substrate.

With the computer-programmed control of time and the release of the stretched substrate, the materials morphed into the designed shape.

In the second method, the designed pattern was directly printed on the stretched ceramic precursor. It was then released under computer-programming control and underwent the self-morphing process.

"With the versatile shape-morphing capability of the printed ceramic precursors, its application can be huge," said Lu.

One promising application is electronics. Ceramic materials have much better performance in transmitting electromagnetic signals than metallic materials.

With the arrival of 5G networks, ceramic products will play a more important role in the manufacture of electronic products.

The artistic nature of ceramics and their capability to form complex shapes also provide the potential for consumers to create custom ceramic mobile phone backplates.