Pitch controls the flexibility of helical ribbons. (January 2023)

• Record Type: Journal Article
• Authors: Prévost, Lucas; Lindner, Anke; du Roure, Olivia
• Is Part Of: Extreme mechanics letters. Volume 58(2023)
• Publication Date: 2023-01
• Subjects: Helices -- Spring -- Microfabrication -- Elastic strips -- Force–extension measurements; Mechanics -- Periodicals; Mechanics, Applied -- Periodicals; Mechanics; Electronic journals; Periodicals; 531.05
• DOI: 10.1016/j.eml.2022.101923
• Languages: English
• ISSNs: 2352-4316

Abstract

Abstract: Helical objects are often implemented in electronic or mechanical micro-systems, requiring a precise understanding of their mechanical properties. While helices formed by cylindrical filaments have been intensely investigated, little is known about the role of the cross-section of the filament at the basis of the helical shape. We study experimentally the force–extension response of micro-helices fabricated from ultra-thin PMMA ribbons. Leveraging newly achieved control on the helix geometry, the influence of the helical pitch is quantified and a significant stiffening of the helical ribbons with increasing pitch is highlighted. Two phenomena are identified: a mechanical transition from a regime dominated by twisting of the ribbon at small pitch to a bending-dominated regime at high pitch and a purely geometrical effect, specific to helical ribbons. Excellent agreement is found with a previously established analytical model of inextensible elastic strips.