Assembly of 3D micro/nanostructures in advanced functional materials has important implications across broad areas of technology. Existing approaches are compatible, however, only with narrow classes of materials and/or 3D geometries. This paper introduces ideas for a form of Kirigami that allows precise, mechanically driven assembly of 3D mesostructures of diverse materials from 2D micro/nanomembranes with strategically designed geometries and patterns of cuts. Theoretical and experimental studies demonstrate applicability of the methods across length scales from macro to nano, in materials ranging from monocrystalline silicon to plastic, with levels of topographical complexity that significantly exceed those that can be achieved using other approaches. A broad set of examples includes 3D silicon mesostructures and hybrid nanomembrane-nanoribbon systems, including heterogeneous combinations with polymers and metals, with critical dimensions that range from 100 nm to 30 mm. A 3D mechanically tunable optical transmission window provides an application example of this Kirigami process, enabled by theoretically guided design.Kirigami | three-dimensional assembly | buckling | membranes T hree-dimensional micro/nanostructures are of growing interest (1-10), motivated by their increasingly widespread applications in biomedical devices (11-13), energy storage systems (14-19), photonics and optoelectronics (20-24), microelectromechanical systems (MEMS) (25-27), metamaterials (21,(28)(29)(30)(31)(32), and electronics (33-35). Of the many methods for fabricating such structures, few are compatible with the highest-performance classes of electronic materials, such as monocrystalline inorganic semiconductors, and only a subset of these can operate at high speeds, across length scales, from centimeters to nanometers. For example, although approaches (36-39) that rely on self-actuating materials for programmable shape changes provide access to a wide range of 3D geometries, they apply only to certain types of materials [e.g., gels (36, 37), liquid crystal elastomers (39), and shape memory alloys (38)], generally not directly relevant to high-quality electronics, optoelectronics, or photonics. Techniques that exploit bending/folding of thin plates via the action of residual stresses or capillary effects are, by contrast, naturally compatible with these modern planar technologies, but they are currently most well developed only for certain classes of hollow polyhedral or cylindrical geometries (1, 10, 40-44). Other approaches (45, 46) rely on compressive buckling in narrow ribbons (i.e., structures with lateral aspect ratios of >5:1) or filaments to yield complex 3D structures, but of primary utility in opennetwork mesh type layouts. Attempts to apply this type of scheme to sheets/membranes (i.e., structures with lateral aspect ratios of <5:1) lead to "kink-induced" stress concentrations that cause mechanical fracture. The concepts of Kirigami, an ancient aesthetic pursuit, involve strategically configured arrays of cuts to gui...

No abstract

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches of origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies and/or capability of control over the transformation. Here, we introduce an approach that exploits controlled mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as an effective strategy to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system-level examples of soccer balls, model houses, cars, and multi-floor textured buildings.

Maize (Zea mays) floury3 (fl3) is a classic semidominant negative mutant that exhibits severe defects in the endosperm but fl3 plants otherwise appear normal. We cloned the fl3 gene and determined that it encodes a PLATZ (plant AT-rich sequence and zinc binding) protein. The mutation in fl3 resulted in an Asn-to-His replacement in the conserved PLATZ domain, creating a dominant allele. Fl3 is specifically expressed in starchy endosperm cells and regulated by genomic imprinting, which leads to the suppressed expression of fl3 when transmitted through the male, perhaps as a consequence the semidominant behavior. Yeast two-hybrid screening and bimolecular luciferase complementation experiments revealed that FL3 interacts with the RNA polymerase III subunit 53 (RPC53) and transcription factor class C 1 (TFC1), two critical factors of the RNA polymerase III (RNAPIII) transcription complex. In the fl3 endosperm, the levels of many tRNAs and 5S rRNA that are transcribed by RNAPIII are significantly reduced, suggesting that the incorrectly folded fl3 protein may impair the function of RNAPIII. The transcriptome is dramatically altered in fl3 mutants, in which the downregulated genes are primarily enriched in pathways related to translation, ribosome, misfolded protein responses, and nutrient reservoir activity. Collectively, these changes may lead to defects in endosperm development and storage reserve filling in fl3 seeds.