ABSTRACT
Constructing crossmodal in-sensor processing system based on high-performance flexible devices is of great significance for the development of wearable human-machine interfaces. A bio-inspired crossmodal in-sensor computing system can perform real-time energy-efficient processing of multimodal signals, alleviating data conversion and transmission between different modules in conventional chips. Here, we report a bio-inspired crossmodal spiking sensory neuron (CSSN) based on a flexible VO2 memristor, and demonstrate a crossmodal in-sensor encoding and computing system for wearable human-machine interfaces. We demonstrate excellent performance in the VO2 memristor including endurance (>1012), uniformity (0.72% for cycle-to-cycle variations and 3.73% for device-to-device variations), speed (<30 ns), and flexibility (bendable to a curvature radius of 1 mm). A flexible hardware processing system is implemented based on the CSSN, which can directly perceive and encode pressure and temperature bimodal information into spikes, and then enables the real-time haptic-feedback for human-machine interaction. We successfully construct a crossmodal in-sensor spiking reservoir computing system via the CSSNs, which can achieve dynamic objects identification with a high accuracy of 98.1% and real-time signal feedback. This work provides a feasible approach for constructing flexible bio-inspired crossmodal in-sensor computing systems for wearable human-machine interfaces.
Subject(s)
Sensory Receptor Cells , Wearable Electronic Devices , Humans , Sensory Receptor Cells/physiology , Man-Machine Systems , Action Potentials/physiology , Equipment DesignABSTRACT
Vanadium dioxide (VO2)-based smart windows show excellent promise for energy-saving and have been extensively researched. However, for the glass industry-compatible magnetron sputtering process, VO2 films are difficult to obtain and have homogeneous crystalline state, leaving them lacking the ideal solar modulation (ΔTsol) and sensitivity (narrow hysteresis loop). More importantly, the instability of VO2 hinders its commercialization. Multilayer structures have been repeatedly investigated to solve these problems. Unfortunately, the mediocre thermochromic properties as well as the complex and expensive manufacturing steps still hinder its commercialization. In this work, we prepared gradient variation oxygen-content vanadium-oxygen composite films (V2O3/VO2/V2O5, VOgv) with enhanced crystallinity and excellent durability by one-step continuous sputtering. According to optical measurements, the ΔTsol of the VOgv films was significantly increased by 145% (from 6.85 to 16.80%) compared to VO2 films, and the width of the hysteresis loop was reduced by 67% (from 19.34 to 6.36 °C), while the VOgv films exhibited a wider preparation window. The accelerated tests have shown that the film has an equivalent service life of approximately 20 years. We exploited the intrinsic similarity in properties of homologous compounds of vanadium oxide and simplified the preparation process, which is supposed to break the existing application bottlenecks and increase the commercializing possibility of VO2-based thermochromic smart windows.
ABSTRACT
Rare-earth oxyhydride (ReOxHy) films are novel inorganic photochromic materials that have strong potential for applications in windows and optical sensors. Cations greatly influence many material properties and play an important role in the photochromic performance of ReOxHy. Here we propose a strategy for obtaining Gd1-zYzOxHy films (z = 1, 0.7, 0.5, 0.4, 0.35, 0.25, 0.15, 0) using one-step direct-current (DC) magnetron co-sputtering. Distinct from the mixed anion systems, such material would belong to the class of mixed anion and mixed cation materials. For Gd1-zYzOxHy films, different co-doping ratios can help tune the contrast ratio (that is, the difference between coloration and bleaching transmittance) and cycling degradation, which may be related to the lattice constant. X-ray diffraction (XRD) patterns show that the lattice constant increases from 5.38 Å for YOxHy to 5.51 Å, corresponding to Gd0.75Y0.25OxHy. The contrast ratio, in particular, can be enhanced to 37% from 6.3% by increasing the lattice constant, directly controlled by the co-sputtering power. When the lattice constant decreases, the surface morphology of the sample with the smallest lattice constant is essentially unchanged by testing in air with normal oxidation for 100 days, suggesting great improvement in environment durability. However, the crystal structure cannot be overly compressed, and co-sputtering with Cr gives black opaque films without photochromic properties. Moreover, because the atomic mass of different rare earth elements is different, the critical pressure p* (films deposited at p < p* remain metallic dihydrides) is different, and the preparation window is enlarged. Our work provides insights into innovative photochromic materials that can help to achieve commercial production and application.
ABSTRACT
Flexible vanadium dioxide (VO2) thermochromic films show great potential for large-scale fabrication and possess broader applications compared with VO2 coatings on rigid substrates. However, the fabrication of flexible VO2 films remains a challenge so far, leading to the scarcity of research on flexible VO2 films for smart windows. With the aim to obtain a flexible VO2-based films with excellent optical properties and a long service life, we designed and successfully fabricated a flexible ITO/VO2/ITO (IVI) film on the colorless transparent polyimide substrate, which could be directly attached to glasses for indoor temperature modulation. This flexible IVI film effectively enhances the luminous transmittance (Tlum) and solar modulation ability (ΔTsol) (15 and 68% increase relative to a VO2 single layer), reduces the thermal emissivity (εT) (50.7% decrease relative to a VO2 single layer), and exhibits better durability than previously reported structures. Such excellent comprehensive performance offers it great potential in practical applications on smart windows. This work is supposed to provide a new strategy for facile direct fabrication of flexible VO2 films and broaden the applications of flexible VO2 in more coatings and devices.