Nematic and cholesteric liquid crystals are three-dimensional fluids that possess long-range orientational ordering and can support both topological defects and chiral superstructures. Implications of this ordering re...
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Nematic and cholesteric liquid crystals are three-dimensional fluids that possess long-range orientational ordering and can support both topological defects and chiral superstructures. Implications of this ordering remain unexplored even for simple dynamic processes such as the ones found in so-called “fall experiments,” or motion of a spherical inclusion under the effects of gravity. Here we show that elastic and surface anchoring interactions prompt periodic dynamics of colloidal microparticles in confined cholesterics when gravity acts along the helical axis. We explore elastic interactions between colloidal microparticles and confining surfaces as well as with an aligned ground-state helical structure of cholesterics for different sizes of spheres relative to the cholesteric pitch, demonstrating unexpected departures from Stokes-like behavior at very low Reynolds numbers. We characterize metastable localization of microspheres under the effects of elastic and surface anchoring periodic potential landscapes seen by moving spheres, demonstrating the important roles played by anchoring memory, confinement, and topological defect transformation. These experimental findings are consistent with the results of numerical modeling performed through minimizing the total free energy due to colloidal inclusions at different locations along the helical axis and with respect to the confining substrates. A potential application emerging from this work is colloidal sorting based on particle shapes and sizes.
The unique structure and properties of graphene initiated broad fundamental and technological research, and highlighted graphene as a new candidate for various applications such as energy storage, solar cells and elec...
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We report the first electrochemical system for the detection of single‐nucleotide polymorphisms (SNPs) that can accurately discriminate homozygous and heterozygous genotypes using microfluidics technology. To achieve...
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We report the first electrochemical system for the detection of single‐nucleotide polymorphisms (SNPs) that can accurately discriminate homozygous and heterozygous genotypes using microfluidics technology. To achieve this, our system performs real‐time melting‐curve analysis of surface‐immobilized hybridization probes. As an example, we used our sensor to analyze two SNPs in the apolipoprotein E ( ApoE ) gene, where homozygous and heterozygous mutations greatly affect the risk of late‐onset Alzheimer’s disease. Using probes specific for each SNP, we simultaneously acquired melting curves for probe–target duplexes at two different loci and thereby accurately distinguish all six possible ApoE allele combinations. Since the design of our device and probes can be readily adapted for targeting other loci, we believe that our method offers a modular platform for the diagnosis of SNP‐based diseases and personalized medicine.
Passive-dynamic ankle-foot orthoses (PD-AFOs) are a common form of assistive braces prescribed to improve gait of patients having impaired ankle joint function. The PD-AFO structural bending response is used to compen...
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ISBN:
(纸本)9781934551158
Passive-dynamic ankle-foot orthoses (PD-AFOs) are a common form of assistive braces prescribed to improve gait of patients having impaired ankle joint function. The PD-AFO structural bending response is used to compensate for a patient's reduced ankle moment. This work focuses on the design and analysis of a carbon fiber based composite PD-AFO that provides a thin, lighter weight alternative to the more commonly used plastic based PD-AFOs. The purpose of this study was to demonstrate feasibility of designing composite PD-AFOs having desired bending stiffness. A custom, 3D surface model of the brace is used to create the overall geometry. The composite lay-up and associated stiffness of the composite PD-AFO is determined numerically, as a function of ankle angle for the foot-flat phase of the gait cycle. It is shown that the brace can be designed to augment the lost natural ankle stiffness of a patient to match that of a healthy person. The results indicate that the geometry of a PD-AFO, composite lay-up and the material properties are key factors in achieving the desired stiffness characteristics. Copyright 2013 by Aurora Flight sciences.
Cortical and trabecular bones were modeled as nanocomposite materials with hierarchical structures spanning from collagen-mineral level to cortical and trabecular bone levels. In order to verify theoretical models, co...
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A stretchable wire‐shaped lithium‐ion battery is produced from two aligned multi‐walled carbon nanotube/lithium oxide composite yarns as the anode and cathode without extra current collectors and binders. The two c...
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A stretchable wire‐shaped lithium‐ion battery is produced from two aligned multi‐walled carbon nanotube/lithium oxide composite yarns as the anode and cathode without extra current collectors and binders. The two composite yarns can be well paired to obtain a safe battery with superior electrochemical properties, such as energy densities of 27 Wh kg −1 or 17.7 mWh cm −3 and power densities of 880 W kg −1 or 0.56 W cm −3 , which are an order of magnitude higher than the densities reported for lithium thin‐film batteries. These wire‐shaped batteries are flexible and light, and 97 % of their capacity was maintained after 1000 bending cycles. They are also very elastic as they are based on a modified spring structure, and 84 % of the capacity was maintained after stretching for 200 cycles at a strain of 100 %. Furthermore, these novel wire‐shaped batteries have been woven into lightweight, flexible, and stretchable battery textiles, which reveals possible large‐scale applications.
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