Curved display based on programming origami tessellations

Curved displays are increasingly sought after in various applications. While flexible displays offer some curvature, they are limited by Gauss's Theorema Egregium, restricting their use to developable surfaces. Stretchable displays, using materials like PDMS or serpentine interconnects, address this limitation but suffer from drawbacks such as low stiffness, short fatigue life, and complex manufacturing processes. Origami-based structures provide a potential solution due to their localized stress and strain during folding. Existing origami approaches, however, often involve compromises such as adding extra creases or inhomogeneous facet sizes. This research introduces a new method that leverages a structure-mechanics-inspired functional optimization method to design Miura-like origami tessellations that minimize in-facet bending, thus allowing compatibility with high-throughput manufacturing processes. The optimization algorithm minimizes pseudostrain energy, ensuring minimal deformation during folding.

The paper reviews existing technologies for creating curved displays, highlighting the limitations of flexible and stretchable displays. Flexible displays, while bending, cannot conform to non-developable surfaces due to Gauss's Theorema Egregium. Stretchable displays, using either stretchable substrates or serpentine interconnects, overcome this limitation but face challenges like low stiffness, short fatigue life, complex manufacturing, high cost, and low yield. The authors discuss prior work utilizing origami for stretchable devices, acknowledging the limitations of previous origami-based approaches, which often require compromises in design or manufacturing to achieve the desired curvature. The authors' approach distinguishes itself by focusing on the optimization of Miura-like origami tessellations for compatibility with high-throughput manufacturing.

The methodology involves three main stages: design, fabrication, and folding. The design stage utilizes a structure-mechanics-inspired optimization algorithm to create Miura-like origami tessellations that minimize in-facet bending during folding. This algorithm minimizes the pseudostrain energy of all facets using a special finite element scheme. The fabrication process employs a silicon-based microfabrication process to create a multilayer flexible circuit board. This board consists of parylene-C layers, copper electrodes, and SU-8 stiffeners that provide rigidity to the facets. LED chips are then placed and soldered onto the board using pick-and-place technology. The final stage involves folding the 2D display into the 3D curved shape using 3D-printed molds that guide the folding process. The molds are designed based on the optimized origami patterns. The folding process involves two steps: inscribe mountain and valley creases and then further bend and fix on the curved surface. The process accounts for misalignments during folding due to the flexibility of the 3D-printed molds and gaps between SU-8 stiffeners.

The researchers successfully fabricated and demonstrated curved LED displays with spherical and saddle shapes. The 4.8 cm × 6 cm spherical display had a 16 × 20 LED array, and the 6 cm × 6 cm saddle-shaped display had a 20 × 20 LED array. A yield higher than 95% was achieved. The displays were functional and displayed letters and patterns. The optimized origami design minimized distortion during folding, maintaining a nearly constant center-to-center distance between neighboring facets, which is beneficial for LED chip mounting and display quality. The folding process, aided by 3D-printed molds, successfully transformed the flat 2D displays into 3D curved structures. The maximum torsion angle of the crease centerline was measured to be 8°, and the offset at both ends of the crease was 200 µm. The pixel pitch after folding was approximately 2 mm. The curved displays exhibited minimal distortion despite the folding process.

This research successfully demonstrates a novel method for fabricating curved displays using programmed origami tessellations. The approach addresses the limitations of existing flexible and stretchable display technologies by combining the benefits of origami's localized stress and strain behavior with optimized design principles and high-throughput manufacturing processes. The resulting displays exhibit good functionality and are compatible with nondevelopable surfaces. The optimized origami design and the use of 3D-printed molds contribute to the high yield and efficiency of the fabrication process. This approach has significant implications for the development of next-generation curved displays for various applications.

This study presents a novel and scalable method for manufacturing curved displays using programmed origami tessellations. The integration of structural optimization, microfabrication, and mold-guided folding enables the creation of functional curved displays with high yield. This technology holds promise for advancing the application of next-generation curved displays in various fields. Future work could explore different origami patterns, materials, and display technologies to further optimize the design and expand the applications of this approach.

The current study focuses on relatively small displays. Scaling up the fabrication process for larger displays would require further optimization. The accuracy of the folding process could be further improved to reduce distortion in the final curved display. The range of achievable curvatures could be limited by the design of the origami patterns and the properties of the materials used. Further research should explore the long-term durability and reliability of these displays under different environmental conditions.