More Activity Means Less Response in Active Materials

For years, researchers have assumed that increasing the activity of microscopic components in solid materials would lead to stronger, more useful macroscopic responses. This intuition has guided the design of active materials—systems where energy-consuming parts generate motion or force—aimed at applications ranging from soft robotics to adaptive implants. However, recent research reveals a surprising inversion of this expectation: in certain conditions, more microscopic activity can actually suppress the material’s large-scale response.

This counterintuitive phenomenon, dubbed “more is less,” emerges in a class of materials known as unpercolated active solids. In these systems, the active components—such as self-propelled particles or molecular motors—are not sufficiently connected to form a continuous network across the material. Below a critical threshold of connectivity, called the percolation threshold, increasing activity does not amplify the overall response. Instead, it triggers non-affine and localized modes of motion that disrupt coordinated behavior at the macroscale.

As activity rises, the internal dynamics develop into increasingly heterogeneous. Rather than deforming uniformly, the material develops pockets of intense, localized activity that do not contribute to net shape change or force generation. These localized fluctuations effectively cancel out any potential large-scale response, causing the macroscopic signature of activity to vanish even as the microscopic components become more energetic.

The discovery stems from a combination of metamaterial experiments and coarse-grained theoretical modeling. Researchers observed that in disordered or periodically structured active solids below the percolation point, higher activity leads to a decay in the measurable macroscopic response. This behavior is not a limitation of measurement but a fundamental feature of the material’s internal dynamics.

Importantly, the “more is less” effect does not imply that active materials are ineffective. Rather, it highlights a design principle: to harness macroscopic functionality, the active components must be sufficiently connected to allow coordinated motion. Above the percolation threshold, increased activity can once again enhance the material’s response, restoring the expected relationship between micro-scale activity and macro-scale behavior.

This insight has significant implications for the engineering of active matter. It suggests that simply making components more active is not always beneficial and that structural connectivity plays a critical role in determining performance. Future designs of active solids for applications such as adaptive locomotion, shape-morphing structures, or energy-harvesting devices may need to prioritize network connectivity alongside component activity to avoid the “more is less” regime.

By revealing this non-intuitive behavior, the research advances our understanding of how energy dissipation and internal coordination govern the emergent properties of active materials. It underscores that in non-equilibrium systems, more energy input does not necessarily translate to more useful output—and that sometimes, less activity, or better-connected activity, can yield greater macroscopic response.