Linearly polarized elastic waves propagating in a linear path have been extensively explored in numerous applications from biomedical imaging to structural health monitoring; however, elastic waves propagating in a circularly polarized helical path have been less explored because of the challenges in their generation and control. In this paper, we harness conventional actuation methods combined with sheets decorated with Archimedean spirals to generate elastic helical waves. We show that our metamaterials can support the propagation of such waves along a curved path in a topologically protected manner. Moreover, we also show the creation and propagation of helical waves in our metamaterials without the need for wave guiding or domain interfaces, all with a single-mode excitation source. We establish our methodology for flat plates and show the wave evolution as the metamaterials transition from slightly curved plates to fully curved cylinders. We observe the preservation of topologically protected edge states and helical-wave beaming at different frequencies without the need for domain interfaces. Furthermore, we leverage these modes to tune the helicity of the propagating waves. Our methodology opens previously inaccessible avenues for the generation and control of elastic helical waves using single-source actuation, which can be applied in numerous applications.

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• Band gap
• Classical mechanics
• Elastic waves
• Topological effects in acoustic systems
• Acoustic metamaterials
• Mechanical metamaterials
• Topological insulators
• Topological metamaterials