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A published in Nature Communications presents a way to create deployable structures that transform from compact folded states into expansive configurations with perfectly smooth surfaces.

Engineering systems that utilize origami-inspired folding mechanisms have become a focal point in the development of compact and functional designs for aerospace, emergency, and medical applications.

Applying origami to practical scenarios becomes highly complex and challenging when thick materials are required to ensure motion accuracy and structural robustness. When folding thick materials, the accumulation of material thickness causes structural interference, making folding or deployment difficult.

However, conventional thick-panel origami designs suffer from a critical flaw. At valley folds, the surface is disrupted by grooves and gaps, which prevents its use in scenarios that demand a continuous, unbroken surface.

The research, led by Rui Peng from the National University of Singapore and Gregory S. Chirikjian, from the University of Delaware, addresses this long-standing challenge.

ÃÈÃÃÉçÇø spoke to co-author Prof. Chirikjian about the work.

"Existing methods often introduce structural complexities or fail to guarantee seamless surfaces, which significantly limits their practical applicability," explains Prof. Chirikjian. "Our motivation is to expand the application scope of thick origami techniques by addressing these limitations."

Eliminating not adding

The researchers developed an innovative method that seems to defy conventional engineering logic. Instead of adding elements, they remove specific panels entirely.

A small region of the overall structure consists of three panels connected by two valley creases or concave folds. The researchers addressed the gap in the deployed structure by removing the middle panel and extending the panels on either side.

The approach works because the origami structure is inherently overconstrained. The researchers achieve a simpler design by removing certain panels, all while preserving the structure's functionality.

The success lies in satisfying specific geometric constraints, which have two key steps to ensure motion compatibility.

"First, the structure is based on a rigid origami tube that must satisfy certain symmetrical geometric conditions. Second, after selectively removing some panels and extending their adjacent ones, the extension length must meet a specific geometric constraint related to the panel thickness," said Prof. Chirikjian.

The use of a strict mathematical approach ensures the structures continue to fold as intended, even as surface gaps are eliminated.

Versatility and scalability

The researchers proved the versatility of their design strategy by applying it to construct deployable structures with varied geometries. This indicates that the structures are suitable for a variety of applications across multiple scales.

For large-scale architectural applications, these structures could enable deployable stadium domes, water-tight roofing systems, and space telescopes.

At the consumer level, it can be used for convertible car components. At the tiniest scales, these structures could be valuable in soft robotic systems designed for surgical applications.

As Prof. Chirikjian explained, "We proposed a general methodology for deployable structures that is not limited to any specific application. This approach is highly versatile and can be adapted to a wide range of use cases."

The researchers also developed methods to minimize the number of top (yellow) panels, simplifying fabrication while maintaining functionality. This offers engineers the flexibility to customize the structures based on the requirements.

Looking ahead

By fabricating 3D-printed prototypes, the researchers verified that their designs fold efficiently and expand into seamless surfaces.

The yellow surfaces on top are completely seamless in the deployed state, while the blue panels below act as a support structure.

"These structures do not have strict material requirements, allowing for a wide range of material choices. However, fabrication and assembly techniques play a critical role in determining structural performance, particularly due to the large number of interconnected joints involved," explained Prof. Chirikjian.

The research represents a crucial engineering step in creating smooth, uninterrupted surfaces that offer engineers a practical solution for a wide range of applications.

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