Chemical and Biomedical Engineering - Research Publications
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ItemDetecting Subtle Vibrations Using Graphene-Based Cellular Elastomers(AMER CHEMICAL SOC, 2017-04-05)Ultralight graphene elastomer-based flexible sensors are developed to detect subtle vibrations within a broad frequency range. The same device can be employed as an accelerometer, tested within the experimental bandwidth of 20-300 Hz as well as a microphone, monitoring sound pressures from 300 to 20 000 Hz. The sensing element does not contain any metal parts, making them undetectable by external sources and can provide an acceleration sensitivity of 2.6 mV/g, which is higher than or comparable to those of rigid Si-based piezoresistive microelectromechanical systems (MEMS).
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ItemSuper-carbon spring: a biomimetic design(SCIENCE PRESS, 2017-02)
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ItemExtremely Low Density and Super-Compressible Graphene Cellular Materials(WILEY-V C H VERLAG GMBH, 2017-09-27)Development of extremely low density graphene elastomer (GE) holds the potential to enable new properties that traditional cellular materials cannot offer, which are promising for a range of emerging applications, ranging from flexible electronics to multifunctional scaffolds. However, existing graphene foams with extremely low density are generally found to have very poor mechanical resilience. It is scientifically intriguing but remains unresolved whether and how the density limit of this class of cellular materials can be further pushed down while their mechanical resilience is being retained. In this work, a simple annealing strategy is developed to investigate the role of intersheet interactions in the formation of extreme-low-density of graphene-based cellular materials. It is discovered that the density limit of mechanically resilient cellular GEs can be further pushed down as low as 0.16 mg cm-3 through thermal annealing. The resultant extremely low density GEs reveal a range of unprecedented properties, including complete recovery from 98% compression in both of liquid and air, ultrahigh solvent adsorption capacity, ultrahigh pressure sensitivity, and light transmittance.
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ItemControlled Gelation of Graphene Towards Unprecedented Superstructures(WILEY-V C H VERLAG GMBH, 2017-09-27)Graphene exhibits a range of exceptional physical properties and holds great promise for development of novel bulk materials for widespread applications. Properly engineering of assembled structures of graphene at multiple length scales is essential to realize its full potential in bulk forms. In this Concept article, we highlight the unique colloidal and gelation behavior of a commonly used precursor for graphene, graphene oxide (GO), and discuss how the colloidal chemistry of GO and reduced GO can enable new scalable and cost-effective approaches to construct graphene-based soft superstructures with excellent properties.
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ItemMultifunctional Cellular Materials Based on 2D Nanomaterials: Prospects and Challenges(WILEY-V C H VERLAG GMBH, 2018-01-25)Recent advances in emerging 2D nanomaterial-based cellular materials (2D-CMs) open up new opportunities for the development of next generation cellular solids with exceptional properties. Herein, an overview of the current research status of 2D-CMs is provided and their future opportunities are highlighted. First, the unique features of 2D nanomaterials are introduced to illustrate why these nanoscale building blocks are promising for the development of novel cellular materials and what the new features of 2D nanoscale building blocks can offer when compared to their 0D and 1D counterparts. An in-depth discussion on the structure-property relationships of 2D-CMs is then provided, and the remarkable functions that can be achieved by engineering their cellular architecture are highlighted. Additionally, the use of 2D-CMs to tackle key challenges in different practical applications is demonstrated. In conclusion, a personal perspective on the challenges and future research directions of 2D-CMs is given.
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ItemIon transport in complex layered graphene-based membranes with tuneable interlayer spacing(AMER ASSOC ADVANCEMENT SCIENCE, 2016-02)Investigation of the transport properties of ions confined in nanoporous carbon is generally difficult because of the stochastic nature and distribution of multiscale complex and imperfect pore structures within the bulk material. We demonstrate a combined approach of experiment and simulation to describe the structure of complex layered graphene-based membranes, which allows their use as a unique porous platform to gain unprecedented insights into nanoconfined transport phenomena across the entire sub-10-nm scales. By correlation of experimental results with simulation of concentration-driven ion diffusion through the cascading layered graphene structure with sub-10-nm tuneable interlayer spacing, we are able to construct a robust, representative structural model that allows the establishment of a quantitative relationship among the nanoconfined ion transport properties in relation to the complex nanoporous structure of the layered membrane. This correlation reveals the remarkable effect of the structural imperfections of the membranes on ion transport and particularly the scaling behaviors of both diffusive and electrokinetic ion transport in graphene-based cascading nanochannels as a function of channel size from 10 nm down to subnanometer. Our analysis shows that the range of ion transport effects previously observed in simple one-dimensional nanofluidic systems will translate themselves into bulk, complex nanoslit porous systems in a very different manner, and the complex cascading porous circuities can enable new transport phenomena that are unattainable in simple fluidic systems.
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ItemEngineering graphene for high-performance supercapacitors: Enabling role of colloidal chemistry(ELSEVIER SCIENCE BV, 2018-01)
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ItemHigh-Rate and High-Volumetric Capacitance of Compact Graphene-Polyaniline Hydrogel Electrodes(WILEY-V C H VERLAG GMBH, 2016-06-08)
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ItemLow-voltage electrostatic modulation of ion diffusion through layered graphene-based nanoporous membranes(NATURE PUBLISHING GROUP, 2018-08)Ion transport in nanoconfinement differs from that in bulk and has been extensively researched across scientific and engineering disciplines1-4. For many energy and water applications of nanoporous materials, concentration-driven ion diffusion is simultaneously subjected to a local electric field arising from surface charge or an externally applied potential. Due to the uniquely crowded intermolecular forces under severe nanoconfinement (<2 nm), the transport behaviours of ions can be influenced by the interfacial electrical double layer (EDL) induced by a surface potential, with complex implications, engendering unusual ion dynamics5-7. However, it remains an experimental challenge to investigate how such a surface potential and its coupling with nanoconfinement manipulate ion diffusion. Here, we exploit the tunable nanoconfinement in layered graphene-based nanoporous membranes to show that sub-2 nm confined ion diffusion can be strongly modulated by the surface potential-induced EDL. Depending on the potential sign, the combination and concentration of ion pairs, diffusion rates can be reversibly modulated and anomalously enhanced by 4~7 times within 0.5 volts, across a salt concentration gradient up to seawater salinity. Modelling suggests that this anomalously enhanced diffusion is related to the strong ion-ion correlations under severe nanoconfinement, and cannot be explained by conventional theoretical predictions.