Nanoparticle-coated separators for lithium-ion batteries with advanced electrochemical performance

We report a simple, scalable approach to improve the interfacial characteristics and, thereby, the performance of commonly used polyolefin based battery separators. The nanoparticle-coated separators are synthesized by first plasma treating the membrane in oxygen to create surface anchoring groups followed by immersion into a dispersion of positively charged SiO(2) nanoparticles. The process leads to nanoparticles electrostatically adsorbed not only onto the exterior of the surface but also inside the pores of the membrane. The thickness and depth of the coatings can be fine-tuned by controlling the ζ-potential of the nanoparticles. The membranes show improved wetting to common battery electrolytes such as propylene carbonate. Cells based on the nanoparticle-coated membranes are operable even in a simple mixture of EC/PC. In contrast, an identical cell based on the pristine, untreated membrane fails to be charged even after addition of a surfactant to improve electrolyte wetting. When evaluated in a Li-ion cell using an EC/PC/DEC/VC electrolyte mixture, the nanoparticle-coated separator retains 92% of its charge capacity after 100 cycles compared to 80 and 77% for the plasma only treated and pristine membrane, respectively.     

Generation of core-shell microcapsules with three-dimensional focusing device for efficient formation of cell spheroid

We present a microfluidic device generating three-dimensional (3D) coaxial flow by the addition of a simple hillock to produce an alginate core-shell microcapsule for the efficient formation of a cell spheroid. A hillock tapered at downstream of the two-dimensional focusing channel enables outside flow to enclose the core flow. The aqueous solution in the core flow was focused and surrounded by 1.8% alginate solution to be solidified as a shell. The double-layered coaxial flow (aqueous phase) was broken up into a droplet by the shear flow of oleic acid (oil phase) containing calcium chloride for the polymerization of the alginate shell. The droplet generated from the laminar coaxial flow maintained a double-layer structure and gelation of the alginate solution made a core-shell microcapsule. The shell-thickness of the microcapsule was adjusted from 8-21 μm by the variation of two aqueous flow rates. The inner shape of the shell was almost spherical when the ratio of the water-glycol mixture in the core flow exceeded 20%. The microcapsule was used to form a spheroid of embryonic carcinoma cells (embryoid body; EB) by injecting a cell suspension into the core flow. The cells inside the microcapsule aggregated into an EB within 2 days and the EB formation rate was more than 80% with strong compaction. The microcapsule formed single spherical EBs without small satellite clusters or a bumpy shape as observed in solid microbeads. The microfluidic chip for encapsulation of cells could generate a number of EBs with high rate of EB formation when compared with the conventional hanging drop method. The core-shell microcapsule generated by 3D focusing in the microchannel was effective in forming large number of spherical cell clusters and the encapsulation of cells in the microcapsule is expected to be useful in the transplantation of islet cells or cancer stem cell enrichment.     

Two‐Photon Probes for Zn2+ Ions with Various Dissociation Constants. Detection of Zn2+ Ions in Live Cells and Tissues by Two‐Photon Microscopy

A series of Zn²⁺‐selective two‐photon fluorescent probes (AZnM1−AZnN) that had a wide range of dissociation constants (K_d^TP=8 nm‐ 12 μM ) were synthesized. These probes showed appreciable water solubility (>3 μM ), cell permeability, high photostability, pH insensitivity at pH>7, significant two‐photon action cross‐sections (86–110 GM) upon complexation with Zn²⁺, and can detect the Zn²⁺ ions in HeLa cells and in living tissue slices of rat hippocampal at a depth of >80 μm without mistargeting and photobleaching problems. These probes can potentially find application in the detection of various amounts of Zn²⁺ ions in live cells and intact tissues.     

Treatment of TiO2 with COOH‐Functionalized Germanium Nanoparticles to Enhance the Photocurrent of Dye‐Sensitized Solar Cells

A dye‐sensitized solar cell (DSSC) containing a TiO₂ film treated with COOH‐functionalized germanium nanoparticles (Ge COOH Nps) exhibited a higher short‐circuit photocurrent density (J_sc; 15.4 mA cm⁻²) compared to the corresponding untreated DSSC (13.4 mA cm⁻²) using N719 and a 12 μm thick TiO₂ film at 100 mW cm⁻². The amount of N719 attached to the treated TiO₂ film was 21 % greater than that attached to the untreated TiO₂ film. Enhancement of the J_sc value by 15 % was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge COOH Nps to the TiO₂ conduction band through the Ge COOH Nps.     

New,real fundamental solutions to the transient thermal contact problem in a piezoelectric strip under the coupling actions of a rigid punch and a convective heat supply

A thermo-electro-mechanical contact analysis has been performed for a finite piezoelectric strip, which is subjected to the joint actions of a rigid, flat punch and a transient convective heat supply. The Laplace transform and Fourier sine and cosine transforms were applied in solving the governing equations. A detailed analysis of the characteristic roots of the corresponding characteristic equation was made. Real fundamental solutions were derived, which can readily lead to real solutions to the thermo-electro-mechanical quantities. A Cauchy-type singular integral equation was obtained for the stated problem and then solved numerically. Closed form solutions of a special case were obtained. To obtain the accurate solution in the time domain, an effective numerical inversion algorithm of the Laplace transform was applied. Detailed analyses were performed to reveal the variation law of temperature, contact stress beneath the punch, stress intensity factor at the punch edge and strain with time. Parametric studies were performed to discover the effects of the layer thickness on the distribution of temperature, contact stress beneath the punch and stress intensity factor at the punch edge.