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1. Magneto-origami structures: Engineering multi-stability and dynamics via magnetic-elastic coupling

   https://doi.org/10.1088/1361-665X/ab524e  

   Fang, Hongbin ; Chang, Tse-Shao ; and Wang, K.W. ( June 2019 , Smart materials and structures)

   Origami provides a flexible platform for constructing three-dimensional multi-stable mechanical metamaterials and structures. While possessing many interesting features originating from folding, the development of multi-stable origami structures is faced with tremendous demands for acquiring tunability and adaptability. Through an integration of origami folding with magnets, this research proposes a novel approach to synthesize and harness multi-stable magneto-origami structures. Based on the stacked Miura-ori and the Kresling ori structures, we reveal that the embedded magnets could effectively tune the structure’s potential energy landscapes, which includes not only altering the position and the depth of the potential wells but essentially eliminating the intrinsic potential wells or generating new potential wells. Such magnet-induced evolutions of potential energy landscapes would accordingly change the origami structure’s stability profiles and the constitutive force–displacement relations. Based on proof-ofconcept prototypes with permeant magnets, the theoretically predicted effects of magnets are verified. The exploration is also extended to the dynamics realm. Numerical studies suggest that the incorporated magnets not only could translate the critical frequencies for achieving certain dynamical behaviors but also fundamentally adjust the frequency-amplitude relationship. Overall, this study shows that the proposed approach would provide a novel means to control the stability profile as well as themore »mechanics and dynamic characteristics of origami structures, and thus, inspire new innovations in designing adaptive mechanical metamaterials and structures.« less
2. Influence of Oxygen Vacancy and Top Electrode on Switching Behavior of InGaZnO Based Resistive Random Access Memory

   Qin, Fei ; Lee, Sunghwan ( June 2022 , 64th Electronic Materials Conference)

   Biomimetic synaptic processes, which are imitated by functional memory devices in the computer industry, are a key focus of artificial intelligence (AI) research. It is critical to developing a memory technology that is compatible with Brain-Inspired Computing in order to eliminate the von Neumann bottleneck that restricts the efficiency of traditional computer designs. Due to restrictions such as high operation voltage, poor retention capacity, and high power consumption, silicon-based flash memory, which presently dominates the data storage devices market, is having difficulty meeting the requirements of future data storage device development. The developing resistive random-access memory (RRAM) has sparked intense investigation because of its simple two-terminal structure: two electrodes and a switching layer. RRAM has a resistive switching phenomenon which is a cycling behavior between the high resistance state and the low resistance state. This developing device type is projected to outperform traditional memory devices. Indium gallium zinc oxide (IGZO) has attracted great attention for the RRAM switching layer because of its high transparency and high atomic diffusion property of oxygen atoms. More importantly, by controlling the oxygen ratio in the sputter gas, its electrical properties can be easily tuned. The IGZO has been applied to the thin-film transistor (TFT),more »thus, it is very promising to integrate RRAM with TFT. In this work, we proposed IGZO-based RRAMs. ITO was chosen as the bottom electrode towards achieving a fully transparent memristor. And for the IGZO switching layer, we varied the O2/Ar ratio during the deposition to modify the oxygen vacancy of IGZO. Through the XPS measurement, we confirmed that the higher O2/Ar ratio can lower the oxygen vacancy concentration. We also chose ITO as the top electrode, for the comparison, two active metals copper and silver were tested for the top electrode materials. For our IGZO layer, the best ratio of O2/Ar is the middle value. And copper top electrode device has the most stable cycling switching and the silver one is perfect for large memory window, however, it encounters a stability issue. The optical transmission examination was performed using a UV-Vis spectrometer, and the average transmittance of the complete devices in the visible-light wavelength range was greater than 90%, indicating good transparency. 50nm, 100nm, and 150nm RS layers of IGZO RRAM were produced to explore the thickness dependency on the characteristics of the RS layer. Also, because the oxygen vacancy concentration influences the RS and RRAM performance, the oxygen partial pressure during IGZO sputtering was modified to maximize the property. Electrode selection is critical and can have a significant influence on the device's overall performance. As a result, Cu TE was chosen for our second type of device because Cu ion diffusion can aid in the development of conductive filaments (CF). Finally, between the TE and RS layers, a 5 nm SiO2 barrier layer was used to limit Cu penetration into the RS layer. Simultaneously, this SiO2 inserting layer can offer extra interfacial series resistance in the device, lowering the off current and, as a result, improving the on/off ratio and overall performance. In conclusion, transparent IGZO-based RRAMs have been created. The thickness of the RS layer and the sputtering conditions of the RS layer were modified to tailor the property of the RS layer. A series of TE materials and a barrier layer were incorporated into an IGZO-based RRAM and the performance was evaluated in order to design the TE material's diffusion capabilities to the RS layer and the BE. Our positive findings show that IGZO is a potential material for RRAM applications and overcoming the existing memory technology limitation.« less
3. Topological state transfer in Kresling origami

   https://doi.org/10.1038/s43246-022-00280-0  

   Miyazawa, Yasuhiro ; Chen, Chun-Wei ; Chaunsali, Rajesh ; Gormley, Timothy S. ; Yin, Ge ; Theocharis, Georgios ; Yang, Jinkyu ( September 2022 , Communications Materials)

   Topological mechanical metamaterials have been widely explored for their boundary states, which can be robustly isolated or transported in a controlled manner. However, such systems often require pre-configured design or complex active actuation for wave manipulation. Here, we present the possibility of in-situ transfer of topological boundary modes by leveraging the reconfigurability intrinsic in twisted origami lattices. In particular, we employ a dimer Kresling origami system consisting of unit cells with opposite chirality, which couples longitudinal and rotational degrees of freedom in elastic waves. The quasi-static twist imposed on the lattice alters the strain landscape of the lattice, thus significantly affecting the wave dispersion relations and the topology of the underlying bands. This in turn facilitates an efficient topological state transfer from one edge to the other. This simple and practical approach to energy transfer in origami-inspired lattices can thus inspire a new class of efficient energy manipulation devices.
4. Proportioning energy-dissipating members in strongback braced frames

   Talley, Peter C. ; Denavit ; Mark D. ; Wierschem, Nicholas E. ( January 2023 , Proceedings of the Annual Stability Conference Structural Stability Research Council)

   Many structural systems are susceptible to soft-story instabilities during earthquakes that are lifethreatening and can lead to damage that is too costly to repair. One way to mitigate damage and reduce the potential for soft-story instability is through the addition of an elastic spine that distributes drifts across the height of a structure. One such system is the strongback braced frame, which replaces one side of a buckling-restrained braced frame with a strongback truss. With the strongback providing vertical continuity, an expanded design space is made available for the arrangement of buckling-restrained braces (BRBs) or other energy-dissipating members. An example of this expanded design space is that a designer could opt to not include BRBs at every story. Methods for proportioning the energy-dissipating resistance in strongback braced frames have been proposed. However, most methods don't allow exploitation of the full design space. The objective of this work is to propose and evaluate a potential method of proportioning energy-dissipating members for arbitrary vertical arrangements within strongback braced frames. For a prototypical building, the BRBs are designed in various configurations using existing methods and with the new method. Nonlinear time history analyses of the resulting designs coupled with a rigid strongback aremore »performed and the results are compared. The impacts of overstrength and P-Δ effects are quantified. The findings support the proposed method of BRB design that enables exploration of the wide design space made available by the strongback.« less
5. ON THE DEPLOYMENT OF MULTISTABLE KRESLING ORIGAMI-INSPIRED STRUCTURES

   https://doi.org/10.1115/DETC2019-97427  

   Kidambi, Narayanan ; and Wang, K.W. ( August 2019 , ASME section IX)

   Origami designs have attracted significant attention from researchers seeking to develop new types of deployable structures due to their ability to undergo large and complex yet predictable shape changes. The Kresling pattern, which is based on a natural accumulation of folds and creases during the twistbuckling of a thin-walled cylinder, offers a great example for the design of deployable systems that expand uniaxially into tubes or booms. However, much remains to be understood regarding the characteristics of Kresling-based deployable systems, and their dynamics during the deployment process remain largely unexplored. Hence this research investigates the deployment of Kresling origami-inspired structures, employing a full sixdegree- of-freedom truss-based model to study their dynamics under different conditions. Results show that tuning the initial rotation angle of a structure gives rise to several qualitatively distinct mechanical properties and stability characteristics, each of which has different implications for the design of the deployable systems. Dynamic analyses reveal the robustness of Kresling structures to out-of-axis perturbations while remaining compliant in the axial direction. These findings suggest that Kresling-based designs can form the basis for the development of new types of deployable structures and systems with tunable performance.