Showing papers by "Bao Yang published in 2020"

Smart Textile-Integrated Microelectronic Systems for Wearable Applications

Abstract: The programmable nature of smart textiles makes them an indispensable part of an emerging new technology field. Smart textile-integrated microelectronic systems (STIMES), which combine microelectronics and technology such as artificial intelligence and augmented or virtual reality, have been intensively explored. A vast range of research activities have been reported. Many promising applications in healthcare, the internet of things (IoT), smart city management, robotics, etc., have been demonstrated around the world. A timely overview and comprehensive review of progress of this field in the last five years are provided. Several main aspects are covered: functional materials, major fabrication processes of smart textile components, functional devices, system architectures and heterogeneous integration, wearable applications in human and nonhuman-related areas, and the safety and security of STIMES. The major types of textile-integrated nonconventional functional devices are discussed in detail: sensors, actuators, displays, antennas, energy harvesters and their hybrids, batteries and supercapacitors, circuit boards, and memory devices.

A general method to synthesize and sinter bulk ceramics in seconds.

Abstract: Ceramics are an important class of materials with widespread applications because of their high thermal, mechanical, and chemical stability. Computational predictions based on first principles methods can be a valuable tool in accelerating materials discovery to develop improved ceramics. It is essential to experimentally confirm the material properties of such predictions. However, materials screening rates are limited by the long processing times and the poor compositional control from volatile element loss in conventional ceramic sintering techniques. To overcome these limitations, we developed an ultrafast high-temperature sintering (UHS) process for the fabrication of ceramic materials by radiative heating under an inert atmosphere. We provide several examples of the UHS process to demonstrate its potential utility and applications, including advancements in solid-state electrolytes, multicomponent structures, and high-throughput materials screening.

Scalable aesthetic transparent wood for energy efficient buildings.

Abstract: Nowadays, energy-saving building materials are important for reducing indoor energy consumption by enabling better thermal insulation, promoting effective sunlight harvesting and offering comfortable indoor lighting. Here, we demonstrate a novel scalable aesthetic transparent wood (called aesthetic wood hereafter) with combined aesthetic features (e.g. intact wood patterns), excellent optical properties (an average transmittance of ~ 80% and a haze of ~ 93%), good UV-blocking ability, and low thermal conductivity (0.24 W m−1K−1) based on a process of spatially selective delignification and epoxy infiltration. Moreover, the rapid fabrication process and mechanical robustness (a high longitudinal tensile strength of 91.95 MPa and toughness of 2.73 MJ m−3) of the aesthetic wood facilitate good scale-up capability (320 mm × 170 mm × 0.6 mm) while saving large amounts of time and energy. The aesthetic wood holds great potential in energy-efficient building applications, such as glass ceilings, rooftops, transparent decorations, and indoor panels. Transparent wood composites are promising engineered materials for green energy-efficient building. Here, authors demonstrate novel aesthetic wood with integrated functions of optical transparency, UV-blocking, thermal insulation, and mechanical strength for this sustainable application.

Rapid Processing of Whole Bamboo with Exposed, Aligned Nanofibrils toward a High-Performance Structural Material

Abstract: Lightweight structural materials are critical in construction and automobile applications. In past centuries, there has been great success in developing strong structural materials, such as steels, concrete, and petroleum-based composites, most of which, however, are either too heavy, high cost, or nonrenewable. Biosourced composites are attractive alternatives to conventional structural materials, especially when high mechanical strength is presented. Here we demonstrate a strong, lightweight bio-based structural material derived from bamboo via a two-step manufacturing process involving partial delignification followed by microwave heating. Partial delignification is a critical step prior to microwave heating as it makes the cell walls of bamboo softer and exposes more cellulose nanofibrils, which enables superior densification of the bamboo structure via heat-driven shrinkage. Additionally, microwave heating, as a fast and uniform heating method, can drive water out of the bamboo structure, yet without destroying the material's structural integrity, even after undergoing a large volume reduction of 28.9%. The resulting microwave-heated delignified bamboo structure demonstrates outstanding mechanical properties with a nearly 2-times improved tensile strength, 3.2-times enhanced toughness, and 2-times increased bending strength compared to natural bamboo. Additionally, the specific tensile strength of the modified bamboo structure reaches 560 MPa cm3 g-1, impressive given that its density is low (1.0 g cm-3), outperforming common structural materials, such as steels, metal alloys, and petroleum-based composites. These excellent mechanical properties combined with the resource abundance, renewable and sustainable features of bamboo, as well as the rapid, scalable manufacturing process, make this strong microwave-processed bamboo structure attractive for lightweight, energy-efficient engineering applications.

Low Tortuous, Highly Conductive, and High-Areal-Capacity Battery Electrodes Enabled by Through-thickness Aligned Carbon Fiber Framework.

Abstract: Thick electrode with high-areal-capacity is a practical and promising strategy to increase the energy density of batteries, but development toward thick electrode is limited by the electrochemical performance, mechanical properties, and manufacturing approaches In this work, we overcome these limitations and report an ultrathick electrode structure, called fiber-aligned thick or FAT electrode, which offers a novel electrode design and a scalable manufacturing strategy for high-areal-capacity battery electrodes The FAT electrode uses aligned carbon fibers to construct a through-thickness fiber-aligned electrode structure with features of high electrode material loading, low tortuosity, high electrical and thermal conductivity, and good compression property The low tortuosity of FAT electrode enables fast electrolyte infusion and rapid electron/ion transport, exhibiting a higher capacity retention and lower charge transfer resistance than conventional slurry-casted thick electrode design

An Adhesive Surface Enables High-Performance Mechanical Energy Harvesting with Unique Frequency-Insensitive and Pressure-Enhanced Output Characteristics.

Abstract: Viscoelastic polymer adhesives (VPAs) are common materials broadly used in adhesive tapes for bonding objects tightly in daily life. This work presents a conceptually new strategy of using contact electrification (rather than strong adhesion) of VPAs to directly convert mechanical energy to electric energy, generally showing 202-419% of the electric energy generated by conventional mechanical energy harvesters under the same triggering conditions. More notably, the VPA-based generators (VPAGs) possess unique frequency-insensitive and pressure-enhanced output characteristics. The output power of a VPAG not only does not show regular degradation of performance with the decrease of triggering frequency, but also can be further enhanced by simple introduction of a second VPA layer with a smaller area to increase the applied pressure without the requirement of rising applied force. The average output power density of a VPAG with a second layer of 0.5 cm × 0.5 cm can reach 216.7 µW cm-2 , which is ≈150% larger than that of a VPAG without a second VPA layer. This research is of significance to harvesting the random, irregular, and low-frequency (bio-)mechanical energy that widely exists but is wasted in the environment for both stable electric energy generation and electronic device operation.

Equilibrium Thermodynamic Properties of Aqueous Solutions of Ionic Liquid 1-Ethyl-3-Methylimidazolium Methanesulfonate [EMIM][MeSO 3 ]

Abstract: The ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO3]) has been considered as a promising alternative desiccant to triethylene glycol and lithium bromide commonly used in the industry. In this paper, the water activity coefficient of this binary system was measured from 303 K to 363 K with water concentration from 18% to 92%. The interaction energies between the ionic liquid molecules ($${g}_{22}$$) and between the ionic liquid and water molecules ($${g}_{12}$$) for the [EMIM][MeSO3]/water binary system were determined from the water activity coefficient data using the Non-Random Two-Liquid (NRTL) model. The magnitude of the interaction energy between the [EMIM][MeSO3] and water molecules ($${g}_{12}$$) was found to be in the range of 45~49 kJ/mol, which was about 20% larger than that between the water molecules ($${g}_{11}$$) in the [EMIM][MeSO3]/water system. The large ($${g}_{12}$$) can explain many observed macroscopic thermodynamic properties such as strong hygroscopicity in the ionic liquid [EMIM][MeSO3]. These interaction energies were used to determine the heat of desorption of the [EMIM][MeSO3]/water system, and the obtained heat of desorption was in good agreement with that calculated from the conventional Clausius-Clapeyron Equation.

Gradient coil with external direct cooling for brain magnetic resonance imaging

Abstract: The gradient coil assembly is designed to address a neck-shoulder clearance problem by configuring the coil holder housing with a cylindrical portion modified with a slanted surface and positioning current return elements of the coil pattern at the slanted surface, while positioning the active electrical elements on the cylindrical surface, thus eliminating influence of an undesired magnetic field generated by the current return elements, shortening the coil, and moving the homogeneous field gradient region toward the end of the cylindrical portion of the bore in the coil holder housing. The subject assembly operation is further improved by the direct external cooling approach, where a coolant flows in direct contact with electrical wires of the gradient coil inside the cooling channels in the surface of the coil holder housing.