Tag Archives: 4d printing

4D-printed structure changes shape when placed in water

A team of Harvard researchers have literally added a new dimension to 3D printing – time. They’ve created nature-inspired objects that change their structure in time.

After printing, the 4D orchid is immersed in water to activate its shape transformation.
Credit: Wyss Institute at Harvard University

Biological bodies like plants react and change their form in response to environmental stimuli. While 3D printing has brought us nature-like structures, making said structures adapt like their natural counterparts remains a challenge. Now, scientists from the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed 4D-printed hydrogel composite structures that like plants, change shape when immersed in water.

“This work represents an elegant advance in programmable materials assembly, made possible by a multidisciplinary approach,” said Jennifer Lewis, senior author on the new study. “We have now gone beyond integrating form and function to create transformable architectures.”

The hydrogels they created are programmed to contain precise, localized swelling, so they don’t have the versatility and flexibility that enable changes in plants, but it’s still a promising start.

They aligned tiny cellulose fibers, encoding the hydrogel ink with swelling and stiffness which can be patterned to produce intricate shape changes. The anisotropic nature of the cellulose fibrils gives rise to varied directional properties that can be predicted and controlled. Think of it as wood, which splits more easily along the grain than across it. This simple technique offers surprisingly many folding options:

“Using one composite ink printed in a single step, we can achieve shape-changing hydrogel geometries containing more complexity than any other technique, and we can do so simply by modifying the print path,” said Gladman. “What’s more, we can interchange different materials to tune for properties such as conductivity or biocompatibility.”

The biggest challenge with this technology was developing the right mathematical model for it.

“Our mathematical model prescribes the printing pathways required to achieve the desired shape-transforming response,” said Matsumoto. “We can control the curvature both discretely and continuously using our entirely tunable and programmable method.”

The model’s challenge is to solve the inverse problem. An inverse problem in science is the process of calculating from a set of observations the causal factors that produced them. In this case, the challenge was predicting

what the printing toolpath must be to encode swelling behaviors toward a desired shape.

“It is wonderful to be able to design and realize, in an engineered structure, some of nature’s solutions,” said Mahadevan, who has studied phenomena such as how botanical tendrils coil, how flowers bloom, and how pine cones open and close. “By solving the inverse problem, we are now able to reverse-engineer the problem and determine how to vary local inhomogeneity, i.e., the spacing between the printed ink filaments, and the anisotropy, i.e., the direction of these filaments, to control the spatiotemporal response of these shape-shifting sheets.”

The technology could have applications in printing self-assembling, dynamic microscale structures, especially in medical situations. For example, a structure that changes its shape once it enters the human body, in order to better release its target drug.

carbon_fiber

At MIT’s self-assembly lab, materials turn to life

A highly fascinating and, surprisingly for some, practical new line of research is concerned with programmable materials; composites designed to become highly dynamic in form and function. When subjected to certain environmental ques, like temperature or pressure, these smart materials can morph and adapt to new conditions. MIT, for instance, is working with self-transforming carbon fiber, printed wood grain, custom textile composites and other rubbers/plastics, which offer unprecedented capabilities including programmable actuation, sensing and self-transformation, from a simple material.

Imaging a package that self-assembles in space into a complete satellite, without the need for computer chips or motorized actuators. Industries that could benefit from such smart materials range from  apparel, architecture, product design and manufacturing to aerospace and automotive industries. The ultimate objective is robots without robots.

“Self-Assembly is a process by which disordered parts build an ordered structure through only local interaction. In self-assembling systems, individual parts move towards a final state, wheras in self-organizing systems, components move between multiple states, oscillate and may never come to rest in a final configuration.”

A key technique in the field is 4-D printing, where the fourth dimension is time. These materials change their physical properties and functionality over time based on external stimuli by exploiting the high precision capabilities of 3-D printing. Here are just a couple of programmable material projects fresh off MIT’s Self-Assembly Lab:

Programmable Carbon Fiber

carbon_fiberprogrammable_fiber

carbon fiber programmable

“We’re releasing self-transforming carbon fibre,” Skylar Tibbits, director of Self-Assembly Lab and research scientist at MIT tells WIRED.co.uk. “It’s fully cured but designed to be flexible. What we do is we print with different materials on to the carbon fibre to make it active.”

The programmable carbon fiber has already been eyed by Airbus, which is interested in using the material to replace the need for a robotic mechanism or an opening that causes drag at the top of a jet engine. Because the material changes its shape function of temperature, it can be designed to regulate the airflow for cooling the engine depending on the amount of heat, thus rendering mechanized systems and batteries redundant. In aerospace, the less electronics and mechanical parts you have, the less the risk of failure.

Morphing Supercar Wing

airfoil

The programmable carbon fibre is also being explored by supercar manufacturer Briggs Automotive Company for aerodynamics, working on the first non-mechanical morphing car airfoil.

airfoil

airfoil1

“The airfoil can change in different weather conditions,” Tibbits explains. “So flaps can open up to give them more control or stability in the back, and then they can close down when it gets dry again.”

Programmable Wood

programmable wooden grain

Wood might be the last material you might think of that can be programmable, but scientists at MIT’s Self-Assembly lab proved wood is flexible enough to be turned into smart, self-morphing filaments.

programmable_woodprogrammable_wood1

“Wood for a long time has been used as an active material,” says Tibbits. “If you get wood wet it starts to curl, especially with thin veneer. Now we can actually print with wood grain, so we literally print out the grains that we want. When it gets wet, we can get a really complex and strange or unique transformation because we’re customising our own grain.”

programmable_Wood

“If you have a very simple example to go from a flat sheet to a 90-degree fold, it’s easy,” Tibbits explains. “But especially with a lot of complex grains, it becomes challenging.”

An example of a 4-D structure that morphs in time according to environmental factors. (c) Anna C. Balazs

4D printing may pave way for a new kind of smart materials

A team of scientists, part of a collaborative effort involving multiple Universities from the U.S., are proposing to take 3D printing one step further by adding a new dimension – time. Their work involves building a new class of materials that can morph, change their physical properties and functionality over time based on external stimuli by exploiting the high precision capabilities of 3-D printing.

An example of a 4-D structure that morphs in time according to environmental factors. (c) Anna C. Balazs

An example of a 4-D structure that morphs in time according to environmental factors. (c) Anna C. Balazs

Imagine an automobile coating that changes its structure to adapt to a humid environment or a salt-covered road, better protecting the car from corrosion. Or consider a soldier’s uniform that could alter its camouflage or more effectively protect against poison gas or shrapnel upon contact. The latter example is actually of great importance since the research was recently awarded a $855,000 grant from the United States Army Research Office.

The team includes principal investigator Anna C. Balazs, the Robert v. d. Luft Distinguished Professor of Chemical Engineering in Pitt’s Swanson School of Engineering and a researcher in the computational design of chemo-mechanically responsive gels and composites. Co-investigators are Jennifer A. Lewis, the Hansjo?rg Wyss Professor of Biologically Inspired Engineering at the Harvard School of Engineering and Applied Sciences and an expert in 3D printing of functional materials; and Ralph G. Nuzzo, the G. L. Clark Professor of Chemistry and Professor of Materials Science and Engineering at the University of Illinois, a synthetic chemist who has created novel stimuli-responsive materials.

4D materials

“Rather than construct a static material or one that simply changes its shape, we’re proposing the development of adaptive, biomimetic composites that reprogram their shape, properties, or functionality on demand, based upon external stimuli,” Balazs explained. “By integrating our abilities to print precise, three-dimensional, hierarchically-structured materials; synthesize stimuli-responsive components; and predict the temporal behavior of the system, we expect to build the foundation for the new field of 4D printing.”

The trio of researchers will combine their high-end expertise to manipulate materials at the micro and nano scale using 3-D printing to layer their 4D composites. If you’re not familiar with the tech yet, basically 3D printing involves precision nanoscale depositing of materials, layer by layer, thus crafting high fidelity 3D objects based on a digital model. Since they’re very precise, 3D printers will allow the scientists to build their intricate nano-patterns in specific areas of the structure.

“If you use materials that possess the ability to change their properties or shape multiple times, you don’t have to build for a specific, one-time use,” she explained. “Composites that can be reconfigured in the presence of different stimuli could dramatically extend the reach of 3D printing.”

Since the research will use responsive fillers embedded within a stimuli-responsive hydrogel, Nuzzo says this opens new routes for producing the next generation of smart sensors, coatings, textiles, and structural components.

“The ability to create one fabric that responds to light by changing its color, and to temperature by altering its permeability, and even to an external force by hardening its structure, becomes possible through the creation of responsive materials that are simultaneously adaptive, flexible, lightweight, and strong. It’s this ‘complicated functionality’ that makes true 4D printing a game changer.”