In a groundbreaking exploration at the intersection of physics and materials science, an international team of researchers from Germany and the United States has unveiled a novel class of crystalline solids composed of rotating particles exhibiting unconventional properties previously unseen in conventional materials. Published in the prestigious Proceedings of the National Academy of Sciences, their findings redefine our understanding of crystal behavior under the influence of transverse – or perpendicular – forces, challenging the classical paradigms dominated by central forces such as gravity and electrostatics.
This extraordinary study delves into the physics of so-called “odd crystals,” where the building blocks are not static atoms or molecules but consist of rotors—microscopic entities that spin and interact with each other through forces acting perpendicular to the line connecting their centers. Unlike traditional central interactions which pull or push along a direct axis, these transverse interactions engender a dynamic where particles execute rotational motion around one another, birthing complex structures locked in synchronized rotation.
The concept of “odd elasticity” emerges as a central theme in this research. In stark contrast to standard materials that stretch or compress linearly under deformation, odd elastic materials respond in a counterintuitive way—they twist when pulled. This torsional response is not merely a mechanical curiosity but signals fundamentally new modes of storing and dissipating energy. The researchers demonstrated through intricate modeling that solids built from such rotating components could spontaneously fragment into multiple smaller crystalline rotating domains, a phenomenon unheard of in classical crystallography.
Crucially, the process is reversible. These fragmented domains, or crystallites, can reassemble, indicating a dynamic equilibrium governed by the interplay between rotation speed and fragment size. Remarkably, this behavior runs opposite to typical crystal growth where structures tend to coalesce into larger entities when conditions are thermodynamically favorable, marking a departure into a regime where increased fragmentation and recovery coexist in a delicate balance.
At the heart of the theoretical framework developed by physicist Professor Zhi-Feng Huang and his collaborators lies a comprehensive cross-scale theory that connects microscopic rotor interactions to the emergent macroscopic properties of odd crystals. Their calculations uncover a fundamental relation tying the critical size of rotating fragments to their rotation speed, identifying a natural selection mechanism whereby crystal fragments are stabilized or destabilized depending on their dynamic characteristics.
Beyond the fragmentation dynamics, the team also investigated the nature and behavior of defects within these odd crystals. Unlike defects in conventional crystals—such as dislocations or vacancies—which tend to degrade material properties, defects here possess their own unique dynamics influenced by the underlying rotational forces. More intriguingly, external manipulations can guide the formation and evolution of these defects, opening tantalizing possibilities for tuning and controlling the mechanical and dynamical properties of odd crystalline solids.
The implications of this research stretch far and wide across physics and material science domains. Dr. Michael te Vrugt of the University of Mainz emphasized the universal applicability of their theoretical framework to all systems manifesting transverse interactions. This includes synthetic colloidal suspensions and even biological assemblies, where rotating entities interact in complex environments, potentially informing the design of new biomimetic materials or shedding light on enigmatic biological processes.
An illustrative biological example are starfish embryos studied at MIT, which dynamically rotate around each other due to transverse interactions generated by their swimming motions. Though the biological implications remain speculative, the underlying physics unites these living systems with the exotic non-living odd crystals investigated in the current study, demarcating a new frontier where active matter physics meets materials engineering.
Professor Hartmut Löwen from Heinrich Heine University Düsseldorf highlighted the predictive power of their theory in identifying emergent elastic properties that can be harnessed for technology. The ability to leverage odd elasticity and controlled defect dynamics might lead to entirely new classes of mechanical switches or metamaterials, devices that could exploit twisting responses rather than mere stretching, revolutionizing how mechanical stress and energy flow are manipulated on the microscale.
Underlying these discoveries is the foundational distinction between central and transverse forces. While centuries of physics have emphasized forces acting along the line joining interacting bodies, transverse interactions acting perpendicularly introduce a fundamentally different interaction topology. This departure alters how energy and momentum are distributed, facilitating the spontaneous rotational arrangements that underpin odd crystal formation and dynamics.
The research team, led by Professors Huang and Löwen and enriched by contributions from Raphael Wittkowski and others, is setting a new paradigm for how we conceptualize crystalline order and mechanical response. Their 2025 publication marks a critical milestone, opening avenues for experimental validation and technological innovation exploiting the unusual physics of rotating crystalline solids driven by transverse interactions.
As the scientific community continues to unravel the complexities of such odd crystals, the potential applications could extend beyond traditional solid-state physics, ranging from advanced materials with tailored mechanical responses to new understandings of collective behaviors in biological systems exhibiting transverse interactions. This fusion of disciplines epitomizes the vibrant horizon of contemporary physical sciences, where subtle theoretical insights translate into transformative technological possibilities.
Subject of Research:
Behavior and dynamics of crystalline solids composed of rotating particles interacting via transverse forces, exhibiting odd elasticity and novel fragmentation properties.
Article Title:
Anomalous grain dynamics and grain locomotion of odd crystals
News Publication Date:
21 October 2025
Web References:
10.1073/pnas.2511350122 (https://www.pnas.org/doi/10.1073/pnas.2511350122)
References:
Z.-F. Huang, M. te Vrugt, R. Wittkowski, H. Löwen, Anomalous grain dynamics and grain locomotion of odd crystals, Proceedings of the National Academy of Sciences 122 (42) e2511350122 (2025).
Image Credits:
Wayne State University / Zhi-Feng Huang
Keywords
Colloidal crystals, odd elasticity, rotating crystals, transverse forces, crystallography, defect dynamics, active matter, materials science
