"It's amazing what you can do using simple beams – a building block that's been around hundreds of years. You can do new stuff with a very old, well studied and very simple component."Katia Bertoldi, SEAS

Soft materials are great at absorbing energy – that's why rubber tires are so good at damping the shocks caused by bumps and potholes in the road. But if researchers are going to build autonomous soft systems, like soft robots, they'll need an effective way to transmit energy through soft materials.

Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with colleagues at the California Institute of Technology, have developed a way to send mechanical signals through soft materials. They describe their research in a paper in the Proceedings of the National Academy of Sciences.

"Soft autonomous systems have received a lot of attention because, just like the human body or other biological systems, they can be adaptive and perform delicate movements. However, the highly dissipative nature of soft materials limits or altogether prevents certain functions," said Jordan Raney, postdoctoral fellow at SEAS and first author of the paper. "By storing energy in the architecture itself we can make up for the energy losses due to dissipation, allowing the propagation of mechanical signals across long distances."

Their novel system uses the centuries-old concept of bistable beams – structures that are stable in two distinct states – to store and release elastic energy along the path of a wave. It consists of a chain of bistable elastomeric beams connected by elastomeric linear springs. When those beams are deformed by a mechanical signal, they snap and store the energy in the form of elastic deformation. As a new signal moves down the elastomer, it snaps the beams back into place, releasing the stored energy and sending the signal downstream like a line of dominoes. In this way, the bistable system prevents mechanical signals from dissipating as they move downstream.

"This design solves two fundamental problems in transmitting information through materials," said Katia Bertoldi, associate professor of the natural sciences at SEAS and senior author of the paper. "It not only overcomes dissipation, but it also eliminates dispersive effects, so that the signal propagates without distortion. As such, we maintain signal strength and clarity from start to end."

The beam geometry requires precise fabrication techniques: if the angle or thickness of one beam is off by just one degree or one millimeter, the whole system fails. So the team used advanced 3D printing techniques to fabricate the system.

"We're developing new materials and printing methods that enable the fabrication of soft materials with programmable bistable elements," said Jennifer Lewis, professor of biologically inspired engineering and co-author of the paper.

The team has designed and printed a soft logic gate using this system. The gate, which looks like a tuning fork, can be controlled to act as either an AND gate or an OR gate. "It's amazing what you can do using simple beams – a building block that's been around hundreds of years," said Bertoldi. "You can do new stuff with a very old, well studied and very simple component."

This story is adapted from material from SEAS, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.