On the corner of Vassar Street and Main in Cambridge, Mass., there’s an architectural oddity called the Stata Center.
From the outside, it looks like there couldn’t be anything serious going on there, yet inside there are numerous projects that bring together three material sciences: physics, chemistry, and biology, with AI for research in AI, computational biology, graphics and vision, language and learning, and robotics. The center is the home of Computer Science & Artificial Intelligence Laboratory (CSAIL), MIT’s largest computer science and AI lab, which over the last 50 years has spun off pioneering companies like Boston Dynamics (robotics design), iRobot (consumer robots), Akamai (edge platform), and Dropbox (file-hosting service).
On August 10, 2022, the MIT researchers at CSAIL published a paper titled New programmable materials can sense their own movements. It describes a new material that has tunable mechanical properties. The stuff can register touch and pressure, and because it can be programmed to sense its own movements, it might be ideal for use as a kind of sensitive, intelligent skin for robots. It was made with a 3D printer.
The fact that it can be printed provides many benefits that go along with this type of additive manufacturing, a very cost-effective new form of production. Unlike conventional printers, which sweep over paper in two dimensions, 3D printers move up and down, left and right, and backward and forward. The process is additive, layering on materials. Additive manufacturing has been around since the 1980s when it was first used primarily to produce scale-model prototypes. By the early 2000s, additive manufacturing was creating functional products. Among its advantages is the ability to make small amounts of a product without extensive set-up costs or the encumbrance of supply chains. As Rebecca Linke writes in “Additive manufacturing, explained,” “This makes customizing products, like prosthetics or implants, easier, and could result in better outcomes for patients. Hearing aids, which are customized for each person, are almost entirely additively manufactured.”
The CSAIL new material was printed in a single run on a 3D printer. It’s a lattice incorporating networks of air-filled channels. The report explains, “By measuring how the pressure changes within these channels when the structure is squeezed, bent, or stretched, engineers can receive feedback on how the material is moving. The method opens opportunities for embedding sensors within architected materials, a class of materials whose mechanical properties are programmed through form and composition.”
The co-lead author of the paper, Lillian Chen, proposes ways this could be used. “The idea with this work is that we can take any material that can be 3D printed and have a simple way to route channels throughout it so we can get sensorization with structure. And if you use really complex materials, then you can have motion, perception, and structure all in one.” That includes the possibility of using the technique to create flexible soft robots “with embedded sensors that enable the robots to understand their posture and movements. [And] it might also be used to produce wearable smart devices that provide feedback on how a person is moving or interacting with their environment.”
The reason for embedding the sensors on the struts within the air-filled lattice structure is that with an installation on the outside, the feedback would lack a complete measuring of how the material is being squeezed or is moving or deforming. Chin explains the significance of this latest development moving toward improved robotics: “Materials scientists have been working hard to optimize architected materials for functionality. This seems like a simple, yet really powerful idea to connect what those researchers have been doing with this realm of perception. As soon as we add sensing, then roboticists like me can come in and use this as an active material, not just a passive one.”
Another interesting nuance of printing dimensional materials that MIT is tinkering with is something called 4D printing. It’s a way of adding one more dimension to the forward-back, side-to-side, up-to-down geometry of 3D printing—the dimension of time. The process involves creating a 3D-printed object that, after being printed, can transform itself into another structure by simply exposing it to an external energy source such as heat, light, or some other environmental stimulus. This will allow printing objects beyond the size limits of the printer. For instance, you could create a flat-printed metal structure that will later reform into the curved shape of a car fender, or you could make the separate parts of a stool that will later reassemble itself into something that would either have been too large to print in your printer or would be easier to ship unassembled. You add the fourth dimension to the product in the form of delayed self-assembly. The possibilities being investigated at MIT’s Self-Assembly Lab include: a flat board that will curl itself into the shape of a chair by adding water or light; self-repairing piping systems; clothing that could change itself according to the weather conditions by tightening or loosening the weave; medical stents that could be sent in a collapsed form through the body, to open up when they reach their arterial location; and even self-folding proteins. The Sculpteo blog reports that the University of Wollongong in Australia has developed the first 4D-printed water valve that closes as hot water is poured on it and widens when the temperature goes down. It was printed with a special hydrogel ink that reacts to high temperatures. The researchers explore some of the possibilities in the YouTube video below.
Although it will be a while before 4D printers become widely available, if you do a quick search for 3D-printing services in your area today, you’ll likely find a number of professional makers you can use for your current 3D needs such as new designs, spare parts, or even scale-model prototypes.