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1. Electrodeposition of Pd Intermetallics using Hg-In by the Electrochemical Liquid-Liquid-Solid Method

   https://doi.org/10.1149/1945-7111/ac9bdc  

   Wu, Henry; Maldonado, Stephen (November 2022, Journal of The Electrochemical Society)

   Electrodeposition of Pd from alkaline baths containing Pd(CN) 2 and KCN with liquid metal electrodes has been performed. Data are presented that Pd dissolved into and reacted with the liquid metal electrodes via an electrochemical liquid-liquid-solid (ec-LLS) process. HgPd crystals were obtained with liquid Hg electrodes. On solid In electrodes, In 7 Pd 3 was exclusively formed. In contrast, InPd was the primary product with Hg 1-x In x alloy electrodes. X-ray diffraction, scanning electron microscopy, and electron backscattering diffraction show that the materials were not a pure phase, as minor components of HgPd and In 7 Pd 3 were observed for various liquid Hg-In compositions. A mechanism is proposed where the InPd intermetallic forms through an intermediate phase of HgPd by the substitution of In atoms for the Hg sites of the unit cell. This study thus motivates further exploration of Hg 1-x In x as a versatile medium for intermetallic synthesis by ec-LLS. 

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2. Emergence and control of photonic band structure in stacked OLED microcavities

   https://doi.org/10.1038/s41467-021-26440-3  

   Allemeier, David; Isenhart, Benjamin; Dahal, Ekraj; Tsuda, Yuki; Yoshida, Tsukasa; White, Matthew S. (October 2021, Nature Communications)

   Abstract We demonstrate an electrically-driven metal-dielectric photonic crystal emitter by fabricating a series of organic light emitting diode microcavities in a vertical stack. The states of the individual microcavities are shown to split into bands of hybridized photonic energy states through interaction with adjacent cavities. The propagating photonic modes within the crystal depend sensitively on the unit cell geometry and the optical properties of the component materials. By systematically varying the metallic layer thicknesses, we show control over the density of states and band center. The emergence of a tunable photonic band gap due to an asymmetry-introduced Peierls distortion is demonstrated and correlated to the unit cell configuration. This work develops a class of one dimensional, planar, photonic crystal emitter architectures enabling either narrow linewidth, multi-mode, or broadband emission with a high degree of tunability. 

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3. High Symmetry Metal‐Dielectric Photonic Crystal Organic Light Emitting Diodes With Single‐Cavity Unit Cells

   https://doi.org/10.1002/adom.202201631  

   Allemeier, David; Sobolew, Nicholas; Magnifico, Sean; Henry, Katherine; Abua, Edward; White, Matthew_S (November 2022, Advanced Optical Materials)

   Abstract Vertically‐stacked organic light emitting diode (OLED) microcavities form 1D metal‐dielectric photonic crystals (MDPC) with many degrees of freedom for engineering complex emission profiles. The photonic band structure of the MDPC OLED is determined by the underlying unit cell and is particularly sensitive to the properties of the metallic electrodes. The electronic requirements of microcavity OLED fabrication often necessitate dissimilar metallic electrodes to achieve good performance. This can profoundly impact the photonic properties of a MDPC by doubling the unit cell length. This work presents a MDPC OLED formed with single‐cavity unit cells by employing optically similar Ag alloys as the semi‐transparent electrode materials. The crystal is found to display a single photonic band without a band gap up to eight stacked cavities. The states within the band are evenly‐spaced and clearly resolved, which is critical for applications seeking to utilize specific photonic states. Design considerations are presented for optimizing the photonic behavior of MDPC OLEDs through selective control of the optical properties of metallic alloys. 

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4. Harnessing the anisotropic multistability of stacked-origami mechanical metamaterials for effective modulus programming

   https://doi.org/10.1177/1045389X18781040  

   Sengupta, Sattam; Li, Suyi (June 2018, Journal of Intelligent Material Systems and Structures)

   This study examines a three-dimensional, anisotropic multistability of a mechanical meta material based on a stacked Miura-ori architecture, and investigates how such a unique stability property can impart stiffness and effective modulus programming functions. The unit cell of this metamaterial can be bistable due to the nonlinear relationship between rigid-folding and crease material bending. Such bistability possesses an unorthodox property: the arrangement of elastically stable and unstable equilibria are different along different principal axes of the unit cell, so that along certain axes the unit cell exhibits two force–deformation relationships concurrently within the same range of deformation. Therefore, one can achieve a notable stiffness adaptation via switching between the two stable states. As multiple unit cells are assembled into a metamaterial, the stiffness adaptation can be aggregated into an on-demand modulus programming capability. That is, via strategically switching different unit cells between stable states, one can control the overall effective modulus. This research examines the underlying principles of anisotropic multistability, experimentally validates the feasibility of stiffness adaptation, and conducts parametric analyses to reveal the correlations between the effective modulus programming and Miura-ori designs. The results can advance many adaptive systems such as morphing structures and soft robotics. 

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5. A Study of the Multi-Stability in a Non-Rigid Stacked Miura-Origami Cellular Mechanism

   https://doi.org/10.1115/DETC2021-67670  

   Tao, Jiayue; Li, Suyi (November 2021, Proceedings of the ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference)

   Multi-stable structures have gathered extensive interest because they can provide a broad spectrum of adaptive functions for many engineering systems. Especially, origami sheets with a translational periodicity can be stacked and assembled to form a multi-stable cellular solid, which has emerged as a promising platform to design functional structures. This paper investigates the multi-stability characteristics of a non-rigid stacked Miura-origami mechanism consisting of Miura-ori sheets and accordion-shaped connecting sheets, focusing on the elemental unit cell. A nonlinear mechanical model based on the barhinge approach is established to quantitatively study the unit cell’s multi-stability with intentionally relaxed rigid-folding conditions. Results show that only two stable states are achievable in the unit cell with enforced rigid-folding kinematics. However, if one relaxes the rigid-folding conditions and allows the facet to deform (i.e. non-rigid folding), four stable states are reachable in the unit cell if the crease torsional stiffness of the connecting sheets becomes sufficiently larger than that of the Miura-ori sheets, or the stress-free folding angle deviates away from 0°. A close examination of the potential energy composition of the non-rigid unit cell provides a detailed principle underpinning the multi-stability. By showing the benefits of exploiting facet compliance, this study can become the building blocks for origami-based structures and material systems with a wider variety of novel functionalities. 

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