Realization of active metamaterials with odd micropolar elasticity

• Published in: Nature communications Vol. 12; no. 1; pp. 5935 - 12
• Main Authors: Chen, Yangyang, Li, Xiaopeng, Scheibner, Colin, Vitelli, Vincenzo, Huang, Guoliang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.10.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/1023/303; 639/766/25/3927; Bending modulus; Conservation laws; Elastic properties; Energy; Energy conservation; Feedforward control; Humanities and Social Sciences; Localization; Mechanical properties; Metamaterials; Modulus of elasticity; multidisciplinary; Piezoelectricity; Robot components; Science; Science (multidisciplinary); Shearing; Symmetry
• DOI: 10.1038/s41467-021-26034-z
• ISSN: 2041-1723

Materials made from active, living, or robotic components can display emergent properties arising from local sensing and computation. Here, we realize a freestanding active metabeam with piezoelectric elements and electronic feed-forward control that gives rise to an odd micropolar elasticity absent in energy-conserving media. The non-reciprocal odd modulus enables bending and shearing cycles that convert electrical energy into mechanical work, and vice versa. The sign of this elastic modulus is linked to a non-Hermitian topological index that determines the localization of vibrational modes to sample boundaries. At finite frequency, we can also tune the phase angle of the active modulus to produce a direction-dependent bending modulus and control non-Hermitian vibrational properties. Our continuum approach, built on symmetries and conservation laws, could be exploited to design others systems such as synthetic biofilaments and membranes with feed-forward control loops. Mechanical metamaterials can be engineered with properties not possible in ordinary materials. Here the authors demonstrate and study an active metamaterial with self-sensing characteristics that enables odd elastic properties not observed in passive media.