Researchers at North Carolina State University have introduced an innovative polymer structure, termed the “Chinese lantern,” capable of transforming into over a dozen distinct curved shapes. This remarkable ability to swiftly change form is achieved through compression or twisting of the original configuration. Controlled remotely by a magnetic field, the lantern’s versatility opens up various potential applications across multiple fields.
The foundational design involves cutting a polymer sheet into a diamond-like parallelogram and creating parallel incisions across its center. This process generates a series of identical ribbons connected by solid strips at the top and bottom. When the ends of these strips are connected, the structure resembles a three-dimensional lantern. According to Jie Yin, a professor of mechanical and aerospace engineering and the corresponding author of a study published in the journal Nature Materials, this basic configuration exhibits bistability. It can maintain two stable forms: its original lantern shape and an alternate form resembling a spinning top when compressed.
Yin explained, “If you compress the structure from the top, it will deform until reaching a critical point and then snap into a second stable shape.” This mechanism allows the lantern to store energy during compression. When released, the structure rapidly returns to its original form, demonstrating a quick transition between stable states.
Innovative Shape Variations
The research team, including first author Yaoye Hong, who is now a postdoctoral researcher at the University of Pennsylvania, discovered that the lantern could produce numerous additional shapes by twisting or folding the solid strips. Each variation can exhibit multiple stable states. Some configurations allow for snapping between two forms, while others can switch among up to four stable states, depending on the applied forces.
To manipulate the structure remotely, the researchers attached a thin magnetic film to the solid strip at the base. This advancement enabled them to demonstrate several practical applications, such as a non-invasive gripper for capturing fish, a filter that opens and closes to regulate water flow, and a compact form that can quickly expand into a tall shape to open collapsed tubes.
Mathematical Modeling for Precision
The team also developed a mathematical model that explains how different angles within the structure control both the shape of each variation and the energy storage capacity in each stable state. Hong stated, “This model allows us to program the shape we want to create, how stable it is, and how powerful it can be when stored potential energy is allowed to snap into kinetic energy.” These aspects are vital for engineering shapes capable of fulfilling specific functions.
Looking ahead, Yin expressed aspirations for the application of these lantern units in creating both two-dimensional and three-dimensional architectures. This could lead to significant advancements in shape-morphing mechanical metamaterials and robotics. “We will be exploring that,” Yin added, emphasizing the transformative potential of their research.
The study, titled “Reprogrammable snapping morphogenesis in freestanding ribbon-cluster meta-units via stored elastic energy,” includes contributions from Caizhi Zhou and Haitao Qing, both Ph.D. students at NC State, as well as Yinding Chi, a former Ph.D. student now at Penn. The project was supported by the National Science Foundation under several grants, including 2005374, 2369274, and 2445551.
This groundbreaking research not only highlights the potential of polymer structures in technology but also paves the way for future innovations in various industries.
