Writing words into smart materials

Researchers at AMOLF, EPFL, and Leiden University have developed a new way to store information in mechanical metamaterials. These are artificial materials that have been engineered to exhibit unique properties. In a paper published in Science Advances on May 6, the team shows how one simple signal can cause a response in multiple mechanical elements (material bits) simultaneously. This extraordinary level of control allows them to write all letters of the alphabet into a mechanical system. The discovery could help create future smart materials, soft robots, and remotely controlled devices.

A mechanical version of computer memory

A ‘material bit’ is a small mechanical element that can exist in two stable positions, similar to the 0s and 1s used in digital computers. In this study, the material bits are tiny flexible rubber beams that can snap either left or right. Snapping to the right holds different information from snapping to the left.

Mechanical systems, built from many of these material bits, can potentially store large amounts of information or change their shape and function when needed. But writing many bits at the same time is difficult. Existing methods often require researchers to control each bit separately.

Controlling bits through motion

To solve this problem, the researchers mounted the rubber beams on a rotating platform. They discovered that the beams respond to two factors: the speed at which the platform spins and the level of acceleration.

By carefully using these two factors, the team could decide exactly which material bits would switch and which would remain unchanged. This required designing an ‘orbit’ in the abstract space of driving protocols. This made it possible to write several bits independently using only one dynamic input instead of many separate controls.

“Our dynamic control paradigm offers a versatile route towards smart, remotely operated devices that can function efficiently across a wide range of physical systems applications, from microfluidics and implants, to smart infrastructure and underwater or medical robotics,” summarizes AMOLF group leader Professor Martin van Hecke.

Writing the alphabet

To demonstrate the system, the researchers built a five-bit mechanical memory device at EPFL in Lausanne. They then designed dynamic input signals that could write all 26 uppercase letters of the alphabet using a standard computer encoding system. In one experiment, the device wrote the word ‘ORBIT’, named after the design.

Information in Matter

One of the essential findings of this research is that the rubber beams store information depending on whether they have snapped or not. This demonstrates that information can be encoded directly in matter. At AMOLF, research groups in the Information in Matter theme are exploring this fascinating phenomenon, in systems ranging from plant-fungal networks to the mechanics of light in a nanophotonic structure.

Learn more

• Read the full paper: https://www.science.org/doi/epdf/10.1126/sciadv.aec1606
• Watch the video of the rubber beams mounted on a rotating platform

If you have questions about this research, please contact group leader Martin van Hecke. This research has been published in the journal Science Advances: Dynamic drives allow independent control of material’.