Tag Archives: Wyss Institute

Soft Robots Mimic Biological Movements

At Harvard University, researchers have developed a model for designing soft robots. The special features of these robots include bending as a human index finger does and twisting like a thumb when a single pressure source powers the robots.

For long, scientists have followed a process of trial and error for designing a soft robot that moves organically—twisting as a human wrist does, or bending just like a finger. Now, at the Wyss Institute for Biologically inspired Engineering and the Harvard JA Paulson School of Engineering and Applied Sciences, researchers have developed a method for automatically designing soft actuators that are based on the desired movement. They have published their findings in the Proceedings of the National Academy of Sciences.

To perform the biologically inspired motions, the researchers turned to mathematics modeling for optimizing the design of the actuator. According to Katia Bertoldi, Associate Professor and coauthor of the paper, now they do not design the actuators empirically. The new method allows them to plug in a motion and the model gives them the design of the actuator that will achieve that motion.

Although the design of a robot that can bend as a finger or a knee does can seem simple, it is actually an incredibly complex process in practice. The complications of the design stems from the fact that one single actuator cannot produce the complex motions necessary. According to the first author of the paper, Fionnuala Connolly, who is also a graduate student at SEAS, the design requires sequencing the actuator segments. Each of them performs a different motion, with only a single input actuating them all.

The team uses fiber-reinforced, fluid-powered actuators. Their method uses mathematical modeling for optimizing the design of the actuators, which perform a certain motion. With their method, the team was able to design soft robots that bend and twist just as human fingers and thumbs do.

SEAS have developed an online, open-source resource that provides the new methodology in the form of a Soft Robotic Toolkit. This will assist educators, researchers, and budding innovators in designing, fabricating, modeling, characterizing, and controlling their own soft robots.

The robotics community has long been interested in embedding flexible materials such as cloth, paper, fiber, and other particles including soft fluidic actuators, which consist of elastomeric matrices. These are lightweight, affordable, and easily customizable to a given application.

These multi-material fluidic actuators are interesting as the robotics community can rapidly fabricate them in a multi-step molding process. Only a simple control input such as from a pressurized fluid achieves the combinations of extension, contraction, twisting, and bending. Compared to the existing designs, new design concepts are using fabrication approaches and soft materials for improving the performance of these actuators.

For instance, motivating applications are using soft robotics such as heart assist devices and soft robotic gloves for defining motion and forcing profile requirements. It is possible to embed mechanical intelligence within these soft actuators for achieving these performance requirements with simple control inputs. The challenge lies in the nonlinear nature of the large bending motions the hyper-elastic materials produce, which make it difficult to characterize and predict their behavior.

3D Printers: Change the Shape of Your 3D-Printed Objects

When you print 3D objects on your 3D printers, they remain stable. Other than deteriorating over time, the objects do not change by themselves. However, that may be changing now. Scientists at MIT have created a new technique of printing 3-D objects where you can change the polymers in the object after printing. That means change the color of the object, grow or shrink it, or even change its shape entirely.

Associate Professor of Chemistry at MIT, Jeremiah Johnson led the research, along with Postdoc Mao Chen, and graduate student Yuwei Gu. They have written a paper on the findings, and they call the technique living polymerization. According to the team, the process creates materials whose growth can be stopped and started at will.

As they explain, after printing the material, it is possible to morph it into something else using light, even growing the material further. For instance, the team used a 3-D printed object immersed inside a solution. When they shined Ultra Violet light on the object, while it was still immersed, the resulting chemical reaction released free radicals. The free radicals bound themselves to other monomers within the solution and added them to the original object. According to the team, the process was highly reactive, and damaged the object.

At another study at the Wyss Institute for Biologically inspired Engineering of Harvard University, Dr. Jennifer Lewis is a senior author on a study on shape-shifting objects created using a 3-D printer. The team has devised a technique that allows printed objects to change their shape according to the environment.

According to the researchers at Wyss Institute, the printer creates a structure that can shift its shape. For instance, when immersed in water, the structure folds into complex and beautiful designs. The researchers claim they can adapt the process so that the printed object can fold into prescribed shapes when cooled, heated, or injected with an electrical current.

The researchers are of the opinion the technology could pave the way for generating new types of medical implants. Folding into shape when inserted into the body, such implants could generate a new family of soft electronics. According to Dr. Lewis, this is an elegant advance in the assembly of programmable materials, which a multidisciplinary approach made it possible to achieve. This has taken them farther than merely integrating form and function for creating transformable architectures.

The researchers have published their work in the journal Nature Materials. They say they were inspired by the manner in which plants grow and change their shape over time, as plants and flowers contain microscopic structures as tissues allowing them to change their shape as their environment changes. For instance, depending on temperature and humidity, plant leaves, flowers, and tendrils open or fold up.

Dr. Lewis used a printable hydrogel as it swells when added to water. The team designed specific structures under control that would change shape when placed in water. They derived the hydrogel ink from wood, and the ink had cellulose fibrils very much like the structures in plants that allow them to change shape.