CityU develops the world's first-ever 4D printing for ceramics
August 20, 2018
A research team at City University of Hong Kong (CityU) has achieved a
ground-breaking advancement in materials research by successfully
developing the world's first-ever 4D printing for ceramics, which are
mechanically robust and can have complex shapes. This could turn a new
page in the structural application of ceramics.
Printed ceramic origami mimicking the Sydney Opera House.
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, the CityU team has 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 team was led by Professor LU Jian, Vice-President (Research and
Technology) and Chair Professor of Mechanical Engineering, who is a
distinguished materials scientist with research interests ranging from
fabricating nanomaterials and advanced structural materials to the
computational simulation of surface engineering.
With the development of the elastic precursors, the research team has
achieved one more breakthrough by developing two methods of 4D printing
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.
In this research, the team 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.
The resultant elastomer-derived ceramics are mechanically robust. They
can have a high compressive strength-to-density ratio (547 MPa on 1.6 g
cm-3 microlattice), and they can come in large sizes with high strength
compared to other printed ceramics.
"The whole process sounds simple, but it's not," said Professor Lu.
"From making the ink to developing the printing system, we tried many
times and different methods. 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."
It took more than 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
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.
The innovation was published in the latest issue of top academic journal
Science Advances under the title "Origami and 4D printing of elastomer-derived
ceramic structures". All research team members are from CityU, including
Dr LIU Guo, Research Assistant, Dr ZHAO Yan, Senior Research Associate,
and Dr WU Ge, Research Fellow.
the versatile shape-morphing capability of the printed ceramic
precursors, its application can be huge!" said Professor Lu. One
promising application will be for electronic devices. 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 tailor-make uniquely designed ceramic mobile phone back
Furthermore, this innovation can be applied in the aero industry and
space exploration. "Since ceramic is a mechanically robust material that
can tolerate high temperatures, the 4D-printed ceramic has high
potential to be used as a propulsion component in the aerospace field,"
said Prof Lu.
Riding on the breakthrough in material and 4D-printing technique
advancement, Prof Lu said the next step is to enhance the mechanical
properties of the material, such as reducing its brittleness.