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Memristors are promising candidates for constructing neural networks. However, their dissimilar working mechanism to that of the addressing transistors can result in a scaling mismatch, which may hinder efficient integration. Here, we demonstrate two-terminal MoS2 memristors that work with a charge-based mechanism similar to that in transistors, which enables the homogeneous integration with MoS2 transistors to realize one-transistor-one-memristor addressable cells for assembling programmable network. The homogenously integrated cells are implemented in a 2×2 network array to demonstrate the enabled addressability and programmability. The potential for assembling scalable network is evaluated in a simulated neural network using obtained realistic device parameters, which achieves over 91% pattern recognition accuracy. This study also reveals a generic mechanism and strategy that can be applied to other semiconducting devices for the engineering and homogeneous integration of memristive systems. 

Green chemistry-based non-isocyanate polyurethanes (NIPU) are synthesized and 3D-printed via rapid, projection photopolymerization into compliant mechanisms of 3D structure with spatially-localized material properties. Trimethylolpropane allyl ether-cyclic carbonate is used to couple the unique properties of two types of reaction chemistry: (1) primary diamine-cyclic carbonate ring-opening conjugation for supplanting conventional isocyanate-polyol reactions in creating urethane groups, with the additional advantage of enabling modular segment interchangeability within the diurethane prepolymers; and (2) thiol–ene (click) conjugation for non-telechelic, low monodispersity, quasi-crystalline-capable, and alternating step-growth co-photopolymerization. Fourier transform infrared spectroscopy is used to monitor the functional group transformation in reactions, and to confirm these process-associated molecular products. The extent of how these processes utilize molecular tunability to affect material properties were investigated through measurement-based comparison of the various polymer compositions: frequency-related dynamic mechanical analysis, tension-related elastic-deformation mechanical analysis, and material swelling analysis. Stained murine myoblasts cultured on NIPU slabs were evaluated via fluorescent microscopy for “green-chemistry” affects on cytocompatibility and cell adhesion to assess potential biofouling resistance. 3D multi-material structures with micro-features were printed, thus demonstrating the capability to spatially pattern different NIPU materials in a controlled manner and build compliant mechanisms. 

Technology advancements in history have often been propelled by material innovations. In recent years, two-dimensional (2D) materials have attracted substantial interest as an ideal platform to construct atomic-level material architectures. In this work, we design a reaction pathway steered in a very different energy landscape, in contrast to typical thermal chemical vapor deposition method in high temperature, to enable room-temperature atomic-layer substitution (RT-ALS). First-principle calculations elucidate how the RT-ALS process is overall exothermic in energy and only has a small reaction barrier, facilitating the reaction to occur at room temperature. As a result, a variety of Janus monolayer transition metal dichalcogenides with vertical dipole could be universally realized. In particular, the RT-ALS strategy can be combined with lithography and flip-transfer to enable programmable in-plane multiheterostructures with different out-of-plane crystal symmetry and electric polarization. Various characterizations have confirmed the fidelity of the precise single atomic layer conversion. Our approach for designing an artificial 2D landscape at selective locations of a single layer of atoms can lead to unique electronic, photonic, and mechanical properties previously not found in nature. This opens a new paradigm for future material design, enabling structures and properties for unexplored territories. 

Abstract Thin ferroelectric materials hold great promise for compact nonvolatile memory and nonlinear optical and optoelectronic devices. Herein, an ultrathin in‐plane ferroelectric material that exhibits a giant nonlinear optical effect, group‐IV monochalcogenide SnSe, is reported. Nanometer‐scale ferroelectric domains with ≈90°/270° twin boundaries or ≈180° domain walls are revealed in physical‐vapor‐deposited SnSe by lateral piezoresponse force microscopy. Atomic structure characterization reveals both parallel and antiparallel stacking of neighboring van der Waals ferroelectric layers, leading to ferroelectric or antiferroelectric ordering. Ferroelectric domains exhibit giant nonlinear optical activity due to coherent enhancement of second‐harmonic fields and the as‐resulted second‐harmonic generation was observed to be 100 times more intense than monolayer WS₂. This work demonstrates in‐plane ferroelectric ordering and giant nonlinear optical activity in SnSe, which paves the way for applications in on‐chip nonlinear optical components and nonvolatile memory devices.