World’s first-ever 4D printing for ceramics

Printed ceramic origami mimicking the Sydney Opera House.
CREDIT
City University of Hong Kong

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.

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 of ceramics.

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 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.

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.

“With 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 plates.

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.

Learn more: CityU develops the world’s first-ever 4D printing for ceramics

 

 

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A new 4-D printer can incorporate conductive wiring directly into shape-changing structures for products that could reshape our world

A powerful new 4-D printing technique could one day allow manufacturers to produce electronic devices and their wiring in a single process.
Credit: H. Jerry Qi

From moon landings to mobile phones, many of the farfetched visions of science fiction have transformed into reality. In the latest example of this trend, scientists report that they have developed a powerful printer that could streamline the creation of self-assembling structures that can change shape after being exposed to heat and other stimuli. They say this unique technology could accelerate the use of 4-D printing in aerospace, medicine and other industries.

The researchers are presenting their work today at the 255th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 13,000 presentations on a wide range of science topics.

We are on the cusp of creating a new generation of devices that could vastly expand the practical applications for 3-D and 4-D printing,” H. Jerry Qi, Ph.D., says. “Our prototype printer integrates many features that appear to simplify and expedite the processes used in traditional 3-D printing. As a result, we can use a variety of materials to create hard and soft components at the same time, incorporate conductive wiring directly into shape-changing structures, and ultimately set the stage for the development of a host of 4-D products that could reshape our world.”

4-D printing is an emerging technology that allows 3-D-printed components to change their shape over time after exposure to heat, light, humidity and other environmental triggers. However, 4-D printing remains challenging, in part because it often requires complex and time-consuming post-processing steps to mechanically program each component. In addition, many commercial printers can only print 4-D structures composed of a single material.

Last year, Qi and his colleagues at Georgia Institute of Technology, in collaboration with scientists at the Singapore University of Technology and Design, used a composite made from an acrylic and an epoxy along with a commercial printer and a heat source to create 4-D objects, such as a flower that can close its petals or a star that morphs into a dome. These objects transformed shape up to 90 percent faster than previously possible because the scientists incorporated the tedious mechanical programming steps directly into the 3-D printing process. Building on this work, the researchers sought to develop an all-in-one printer to address other 4-D printing challenges and move the technology closer to practical application.

The machine they ultimately devised combines four different printing techniques, including aerosol, inkjet, direct ink write and fused deposition modeling. It can handle a multitude of stiff and elastic materials including hydrogels, silver nanoparticle-based conductive inks, liquid crystal elastomers and shape memory polymers, or SMPs. SMPs, which are the most common substances used in 4-D printing, can be programmed to “remember” a shape and then transform into it when heated. With this new technology, the researchers can print higher-quality SMPs capable of making more intricate shape changes than in the past, opening the door for a multitude of functional 4-D applications and designs.

The researchers can also use the printer to project a range of white, gray or black shades of light to form and cure a component into a solid. This grayscale lighting triggers a crosslinking reaction that can alter the component’s behavior, depending on the grayscale of shade shined on it. So, for example, a brighter light shade creates a part that is harder, while a darker shade produces a softer part. As a result, these components can bend or stretch differently than other parts of the 4-D structure around them.

The printer can even create electrical wiring that can be printed directly onto an antenna, sensor or other electrical device. The process relies on a direct-ink-write method to produce a line of silver nanoparticle ink. A photonic cure unit dries and coalesces the nanoparticles to form conductive wire. Then, the printer’s ink-jet component creates the plastic coating that encases the wire.

Currently, Qi’s team is also working with Children’s Healthcare of Atlanta to determine whether this new technology could print prosthetic hands for children born with malformed arms.

“Only a small group of children have this condition, so there isn’t a lot of commercial interest in it and most insurance does not cover the expense,” Qi says. “But these children have a lot of challenges in their daily lives, and we hope our new 4-D printer will help them overcome some of these difficulties.”

Learn more: New 4-D printer could reshape the world we live in

 

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Reverse engineering nature’s ability to grow an infinitely diverse array of shapes paves the way for manufacturing advances

The face of the father of quantum physics, Max Planck, emerges from a flat disk. In each state, the colors show the growth factors of the top (left) and bottom (right) layer, and the thin black lines indicate the direction of growth. The top layer is viewed from the front, and the bottom layer is viewed from the back, to highlight the complexity of the geometries. (Image courtesy of Harvard SEAS)

Researchers develop mathematical techniques for designing shape-shifting shells

Nature has a way of making complex shapes from a set of simple growth rules. The curve of a petal, the swoop of a branch, even the contours of our face are shaped by these processes. What if we could unlock those rules and reverse engineer nature’s ability to grow an infinitely diverse array of shapes?

Scientists from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have done just that. In a paper published in the Proceedings of the National Academy of Sciences, a team of researchers from SEAS and the Wyss Institute for Biologically Inspired Engineering demonstrate a technique to grow any target shape from any starting shape.

“Architect Louis Sullivan once said that ‘form ever follows function’,” said L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology and of Physics and senior author of the study. “But if one took the opposite perspective, that perhaps function should follow form, how can we inverse design form?”

In previous research, the Mahadevan group used experiments and theory to explain how naturally morphing structures — such as Venus flytraps, pine cones and flowers — changed their shape in the hopes of one day being able to control and mimic these natural processes. And indeed, experimentalists have begun to harness the power of simple, bioinspired growth patterns. For example, in 2016, in a collaboration with the group of Jennifer Lewis, the Hansjorg Wyss Professor of Biologically Inspired Engineering at SEAS and Core Faculty Member of the Wyss Institute, the team printed a range of structures that changed its shape over time in response to environmental stimuli.

“The challenge was how to do the inverse problem,” said Wim van Rees, a postdoctoral fellow at SEAS and first author of the paper.  “There’s a lot of research on the experimental side but there’s not enough on the theoretical side to explain what’s actually happening. The question is, if I want to end with a specific shape, how do I design my initial structure?”

Inspired by the growth of leaves, the researchers developed a theory for how to pattern the growth orientations and magnitudes of a bilayer, two different layers of elastic materials glued together that respond differently to the same stimuli. By programming one layer to swell more and/or in a different direction than the other, the overall shape and curvature of the bilayer can be fully controlled. In principle, the bilayer can be made of any material, in any shape, and respond to any stimuli from heat to light, swelling, or even biological growth.

The team unraveled the mathematical connection between the behavior of the bilayer and that of a single layer.

“We found a very elegant relationship in a material that consists of these two layers,” said van Rees. “You can take the growth of a bilayer and write its energy directly in terms of a curved monolayer.”

That means that if you know the curvatures of any shape you can reverse engineer the energy and growth patterns needed to grow that shape using a bilayer.

“This kind of reverse engineering problem is notoriously difficult to solve, even using days of computation on a supercomputer,” said Etienne Vouga, former postdoctoral fellow in the group, now an Assistant Professor of Computer Science at the University of Texas at Austin. “By elucidating how the physics and geometry of bilayers are intimately coupled, we were able to construct an algorithm that solves for the needed growth pattern in seconds, even on a laptop, no matter how complicated the target shape.”

The researchers demonstrated the system by modeling the growth of a snapdragon flower petal from a cylinder, a topographical map of the Colorado river basin from a flat sheet and, most strikingly, the face of Max Planck, one of the founders of quantum physics, from a disk.

“Overall, our research combines our knowledge of the geometry and physics of slender shells with new mathematical algorithms and computations to create design rules for engineering shape,” said Mahadevan. “It paves the way for manufacturing advances in 4-D printing of shape-shifting optical and mechanical elements, soft robotics as well as tissue engineering.”

The researchers are already collaborating with experimentalists to try out some of these ideas.

Learn more: Shaping animal, vegetable and mineral

 

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A new 3-D printing method creates objects that can permanently transform into a range of different shapes

4-D Printed Lattice
A lattice created by a multi-material 3-D printer at Georgia Institute of Technology that can permanently expand to eight times its original width after exposure to heat. (Credit: Rob Felt)

A team of researchers from Georgia Institute of Technology and two other institutions has developed a new 3-D printing method to create objects that can permanently transform into a range of different shapes in response to heat.

The team, which included researchers from the Singapore University of Technology and Design (SUTD) and Xi’an Jiaotong University in China, created the objects by printing layers of shape memory polymers with each layer designed to respond differently when exposed to heat.

“This new approach significantly simplifies and increases the potential of 4-D printing by incorporating the mechanical programming post-processing step directly into the 3-D printing process,” said Jerry Qi, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “This allows high-resolution 3-D printed components to be designed by computer simulation, 3-D printed, and then directly and rapidly transformed into new permanent configurations by simply heating.”

The research was reported April 12 in the journal Science Advances, a publication of the American Association for the Advancement of Science. The work is funded by the U.S. Air Force Office of Scientific Research, the U.S. National Science Foundation and the Singapore National Research Foundation through the SUTD DManD Centre.

Their development of the new 3-D printed objects follows earlier work the team had done using smart shape memory polymers (SMPs), which have the ability to remember one shape and change to another programmed shape when uniform heat is applied, to make objects that could fold themselves along hinges.

“The approach can achieve printing time and material savings up to 90 percent, while completely eliminating time-consuming mechanical programming from the design and manufacturing workflow,” Qi said.

To demonstrate the capabilities of the new process, the team fabricated several objects that could bend or expand quickly when immersed in hot water – including a model of a flower whose petals bend like a real daisy responding to sunlight and a lattice-shaped object that could expand by nearly eight times its original size.

“Our composite materials at room temperature have one material that is soft but can be programmed to contain internal stress, while the other material is stiff,” said Zhen Ding, a postdoc researcher at Singapore University of Technology and Design.  “We use computational simulations to design composite components where the stiff material has a shape and size that prevents the release of the programmed internal stress from the soft material after 3-D printing. Upon heating the stiff material softens and allows the soft material to release its stress and this results in a change – often dramatic – in the product shape.”

The new 4-D objects could enable a range of new product features, such as allowing products that could be stacked flat or rolled for shipping and then expanded once in use, the researchers said. Eventually, the technology could enable components that could respond to stimuli such as temperature, moisture or light in a way that is precisely timed to create space structures, deployable medical devices, robots, toys and range of other structures.

“The key advance of this work is a 4-D printing method that is dramatically simplified and allows the creation of high-resolution complex 3-D reprogrammable products,” said Martin L. Dunn a professor at Singapore University of Technology and Design who is also the director of the SUTD Digital Manufacturing and Design Centre. “It promises to enable myriad applications across biomedical devices, 3-D electronics, and consumer products. It even opens the door to a new paradigm in product design, where components are designed from the onset to inhabit multiple configurations during service.”

Learn more: New 3-D Printing Method Creates Shape-Shifting Objects

 

 

 

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Physical Objects Are About To Become As Programmable As A Computer

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Once we can control any material—from metal to wood to plastic—static objects will become a thing of the past.

Plants moving toward the sun, proteins folding into complex structures in response to their surroundings, molecules stacking themselves together to form a crystal. No external machinery directs these functions. Instead, the structure and shape is embedded in the material properties themselves—a wonder of the natural world.

One day, we may create materials to respond to their environments in similar ways, unlocking a new realm of possibilities for building and design: technologies, products, and infrastructure that are adaptable, efficient, and less prone to costly errors. Imagine smart materials that deliver drugs inside your body just when they’re needed, furniture that assembles itself at your house, or car tires that alter their grip when the road is wet.

“We believe it’s now possible to program nearly every material to change shape and properties,” says Skylar Tibbits, director of MIT’s Self-Assembly Laboratory. Code, he says, will become the “language of materials” in the same way it is the language of machines today.

Tibbits, an architect-turned-computer scientist-turned-mad designer, is at the forefront of popularizing the idea that smarter materials—as much, if not more than, ever-more-complicated machines—will shape the physical world of the future. In a 2013 TED Talk, he introduced a part of this vision by calling it 4-D printing (i.e., 3-D printing with the addition of the dimension of time). Since then, he’s been working to make the idea a reality using real-world materials that manufacturers and product designers use today: wood, textiles, carbon fiber, and more.

An example might help you understand the concept. Tibbits has created a composite wood material that he can 3-D print in flat sheets with customized grains. Depending on the grain pattern, the wood will fold in different ways when water is added. One day, you could get a chair flat-packed shipped, and it could fold itself on arrival.

Research like this is at an early stage, but to Hod Lipson, director of Cornell University’s Creative Machines Lab, it represents a new frontier for product design and manufacturing. First, he says, we’ve created the ability to control the shape of a material via 3-D printers, but one day, we’ll be able to control the properties of materials themselves and, eventually, how those materials behave.

Read more: Physical Objects Are About To Become As Programmable As A Computer

 

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