Giorgio Bazzan

Formation and applications of stable 10 nm to 500 nm supramolecular porphyrinic materials

Nanoscaled materials of organic dyes are of interest for a variety of potential applications because of the rich photonic properties that this class of molecules can impart. One mode to form such nanoscaled materials is via self-organization and self-assembly, using reasonably well understood methods in supramolecular chemistry. But there are inherent complexities that arise from the use of organic-based supramolecular materials, including stability toward dioxygen, structural stability, and nanoarchitectures that may change with environmental conditions. Porphyrinoids have rich photonic properties yet are remarkably stable, have a rigid core, are readily functionalized, and metalation of the macrocycle can impart a plethora of optical, electronic, and magnetic properties. While there are many <10 nm porphyrinic assemblies, which may or may not self-organize into crystals, there is a paucity of 10-500 nm porphyrinic materials that can be isolated and stored. A variety of strategies towards the latter nanoscopic porphyrinic materials are discussed in terms of design, construction, and nanoarchitecture. The hierarchical structures include colloids, nanorods, nanotubes, nanorings, and nano-crystalline materials. This prolegomenon emphasizes the supramolecular chemistry, structure-stability, and structure-function relationships. The goal herein is to examine general trends and delineate general principles.

Origami Actuator Design and Networking Through Crease Topology Optimization

Origami structures morph between 2D and 3D conformations along predetermined fold lines that efficiently program the form of the structure and show potential for many engineering applications. However, the enormity of the design space and the complex relationship between origami-based geometries and engineering metrics place a severe limitation on design strategies based on intuition. The presented work proposes a systematic design method using topology optimization to distribute foldline properties within a reference crease pattern, adding or removing folds through optimization, for a mechanism design. Optimization techniques and mechanical analysis are co-utilized to identify an action origami building block and determine the optimal network connectivity between multiple actuators. Foldable structures are modeled as pin-joint truss structures with additional constraints on fold, or dihedral, angles. A continuous tuning of foldline stiffness leads to a rigid-to-compliant transformation of the local foldline property, the combination of which results in origami crease design optimization. The performance of a designed origami mechanism is evaluated in 3D by applying prescribed forces and finding displacements at set locations. A constraint on the number of foldlines is used to tune design complexity, highlighting the value-add of an optimization approach. Together, these results underscore that the optimization of function, in addition to shape, is a promising approach to origami design and motivates the further development of function-based origami design tools.

Design Optimization Challenges of Origami-Based Mechanisms With Sequenced Folding

Reconfigurable structures based on origami design are useful for multifunctional applications, such as deployable shelters, solar array packaging, and tunable antennas. Origami provides a framework to decompose a complex 2D to 3D transformation into a series of folding operations about predetermined foldlines. Recent optimization toolsets have begun to enable a systematic search of the design space to optimize not only geometry but also mechanical performance criteria as well. However, selecting optimal fold patterns for large folding operations is challenging as geometric nonlinearity influences fold choice throughout the evolution. The present work investigates strategies for design optimization to incorporate the current and future configurations of the structure in the performance evaluation. An optimization method, combined with finite-element analysis, is used to distribute mechanical properties within an initially flat structure to determine optimal crease patterns to achieve desired motions. Out-of-plane and twist displacement objectives are used in three examples. The influence of load increment and geometric nonlinearity on the choice of crease patterns is studied, and appropriate optimization strategies are discussed.

Spatial tuning of a RF frequency selective surface through origami

Origami devices have the ability to spatially reconfigure between 2D and 3D states through folding motions. The precise mapping of origami presents a novel method to spatially tune radio frequency (RF) devices, including adaptive antennas, sensors, reflectors, and frequency selective surfaces (FSSs). While conventional RF FSSs are designed based upon a planar distribution of conductive elements, this leaves the large design space of the out of plane dimension underutilized. We investigated this design regime through the computational study of four FSS origami tessellations with conductive dipoles. The dipole patterns showed increased resonance shift with decreased separation distances, with the separation in the direction orthogonal to the dipole orientations having a more significant effect. The coupling mechanisms between dipole neighbours were evaluated by comparing surface charge densities, which revealed the gain and loss of coupling as the dipoles moved in and out of alignment via folding. Collectively, these results provide a basis of origami FSS designs for experimental study and motivates the development of computational tools to systematically predict optimal fold patterns for targeted frequency response and directionality.

Physical reconfiguration of an origami-inspired deployable microstrip patch antenna array

The physical reconfiguration and deployment of a 2×2 corporate-fed microstrip patch antenna array is investigated. The origami-inspired antenna array reconfigures structurally using a Miura-ori fold pattern to deploy to/from a compact folded state from/to a flat state. The impact of folding on the electromagnetic performance is evaluated across a range of physical states to study the impact of physical reconfiguration. In particular, the input impedance and beamforming capabilities are used to characterize the performance as a function of the primary folding parameter. These performance metrics are impacted by a feed network that extends across the folds and the beamforming capabilities that are impacted by the changing element spacing and orientation. Results from simulation and a fabricated structure are provided for a 2.4 GHz design.

Frequency tuning through physical reconfiguration of a corrugated origami frequency selective surface

Frequency tuning is investigated for a dipole-based frequency selective surface on a corrugated structure through origami folding. Three types of 1D folding patterns that alter the in-plane and out-of-plane element spacing at different rates are used to examine the frequency response in relation to spatial rearrangement. Folding decreases the in-plane spacing and leads to smaller Floquet periodicity lengths and a higher stop-band frequency. In some fold arrangements, folding increases the out-of-plane spacing and results in phase-shift and two distinct coupling modes.