Abstract
The realization of concurrently largely expandable and selectively rigid structures poses a fundamental challenge in modern engineering and materials research. Radially expanding structures in particular are known to require a high degree of deformability to achieve considerable dimension change, which restrains achievable stiffness in the direction of expanding motion. Mechanically hinged or plastically deformable wire-mesh structures and pressurized soft materials are known to achieve large expansion ratios, however often lack stiffness and require complex actuation. Cardiovascular or drug delivery implants are one example which can benefit from a largely expandable architecture that is simple in geometry and intrinsically stiff. Continuous shell cylinders offer a solution with these properties. However, no designs exist that achieve large expansion ratios in such shells when utilizing materials which can provide considerable stiffness. We introduce a new design paradigm for expanding continuous shells that overcomes intrinsic limitations such as poor deformability, insufficient stiffness and brittle behaviour by exploiting purely elastic deformation for self-expandable and ultra-thin polymer composite cylinders. By utilizing shell-foldability coupled with exploitation of elastic instabilities, we create continuous cylinders that can change their diameter by more than 2.5 times, which are stiff enough to stretch a confining vessel with their elastic energy. Based on folding experiments and analytical models we predict feasible radial expansion ratios, currently unmatched by comparable cylindrical structures. To emphasize the potential as a future concept for novel simple and durable expanding implants, we demonstrate the functionality on a to-scale prototype in packaging and expansion and predict feasible constellations of deployment environments.
Highlights
Expandability and stiffness in cylindrical or spherical structures are two fundamentally conflicting properties
Applying this idea to the mechanical boundary conditions of transcatheter aortic valve replacement (TAVR) devices, we show that extreme expansion ratios, even under the influence of a smaller confining vessel like a human artery, do not require shape memory effects, plastic deformation or external driving forces and can be achieved with instability-enhanced functionality[18,19] in continuous polymer composite cylinders
We have introduced a fully novel design principle, which relies on the introduction of controlled instability patterns in stiff polymer composites
Summary
Expandability and stiffness in cylindrical or spherical structures are two fundamentally conflicting properties. Structures where soft materials can not meet stiffness requirements, independent of external actuation, have to deviate from the desirable continuous shells to hinged lattice-8,9 or wire-like architectures[10], which achieve considerable amount of shape change through kinematics[11], plastic deformation[12] or superelasticity[10]. Applying this idea to the mechanical boundary conditions of TAVR devices, we show that extreme expansion ratios, even under the influence of a smaller confining vessel like a human artery, do not require shape memory effects, plastic deformation or external driving forces and can be achieved with instability-enhanced functionality[18,19] in continuous polymer composite cylinders. We demonstrate the functionality using thin-ply laminated carbon fiber reinforced epoxy cylinders
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
