Robotic metamaterial: An endless domino effect

Topological solitons can be found in many places and at many different length scales. For example, they take the form of kinks incoiled telephone cords and large molecules such as proteins. At a very different scale, a black hole can be understood as a topological soliton in the fabric of spacetime. Solitons play an important role in biological systems, being relevant forprotein folding andmorphogenesis - the development of cells or organs.

The unique features of topological solitons - that they can move around but always retain their shape and cannot suddenly disappear - are particularly interesting when combined with so-called non-reciprocal interactions. "In such an interaction, an agent A reacts to an agent B differently to the way agent B reacts to agent A," explains Jonas Veenstra, a PhD student at the University of Amsterdam and first author of the new publication.

Veenstra continues: "Non-reciprocal interactions are commonplace in society and complex living systems but have long been overlooked by most physicists because they can only exist in a system out of equilibrium. By introducing non-reciprocal interactions in materials, we hope to blur the boundary between materials and machines and to create animate or lifelike materials."

TheMachine Materials Laboratory where Veenstra does his research specialises in designing metamaterials: artificial materials and robotic systems that interact with their environment in a programmable fashion. The research team decided to study the interplay between non-reciprocal interactions and topological solitons almost two years ago, when then-students Anahita Sarvi and Chris Ventura Meinersen decided to follow up on their research project for the MSc course 'Academic Skills for Research'.