The constructive interference of surface plasmon polaritons (SPP) launched by nanometric holes allows us to focus SPP into a spot of high near-field intensity having subwavelength width. Near-field scanning optical microscopy is used to map the local SPP intensity. The resulting SPP patterns and their polarization dependence are accurately described in model calculations based on a dipolar model for the SPP emission at each hole. Furthermore, we show that the high SPP intensity in the focal spot can be launched and propagated on a Ag strip guide with a 250 x 50 nm2 cross section, thus overcoming the diffraction limit of conventional optics. The combination of focusing arrays and nano-waveguides may serve as a basic element in planar nano-photonic circuits.

We present the first experimental demonstration of focusing ultrasound waves through a flat acoustic metamaterial lens composed of a planar network of subwavelength Helmholtz resonators. We observed a tight focus of halfwavelength in width at 60.5 KHz by imaging a point source. This result is in excellent agreement with the numerical simulation by transmission line model in which we derived the effective mass density and compressibility. This metamaterial lens also displays variable focal length at different frequencies. Our experiment shows the promise of designing compact and light-weight ultrasound imaging elements.

Metasurfaces with subwavelength thicknesses have exhibited unconventional phenomena in ways that could not be mimicked by traditional materials. Here we report on the analytical design and experimental realizations of acoustic metasurfaces with hitherto inaccessible functionality of manipulating the reflected waves arbitrarily. By suitably designing the phase-shift profile with a 2π span induced by labyrinthine units, the metasurface can reflect acoustic waves in an unusual yet controllable manner. Anomalous reflection and ultrathin planar lenses are both demonstrated with carefully designed metasurfaces. Remarkably, the free manipulation of phase shifts offers great flexibility in the design of nonparaxial acoustic self-accelerating beams with arbitrary trajectories. With extraordinary wave-steering ability, the metasurface should open exciting possibilities for designing compact acoustic components with versatile potential and may find a variety of applications ranging from ultrasound imaging to caustic engineering where designing the shape of a focused trajectory of sound is required.

The generation of surface plasmon polaritons (SPP's) at isolated nanoholes in 100 nm thick Au films is studied using near-field scanning optical microscopy (NSOM). Finitedifference time-domain calculations, some explicitly including a model of the NSOM tip, are used to interpret the results. We find the holes act as point-like sources of SPP's and demonstrate that the interference between the SPP and a directly transmitted wave allows for the determination of the wavelength, phase, and decay length of the SPP. The nearfield intensity patterns can be manipulated by varying the angle and polarization of the incident beam.

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A general and versatile biomimetic approach to synthesize water dispersible and functionalizable upconverting nanoparticles (UCNPs) for selective imaging of live cancer cells is reported. The approach involves coating the surface of UCNPs with a monolayer of phospholipids containing different functional groups, allowing for conjugation of many molecules for a wide range of applications in fields such as bioinspired nanoassembly, biosensing, and bio-medicine.

Establishing the 3D architecture and morphometry of the intact pulmonary acinus is an essential step toward a more complete understanding of the relationship of lung structure and function. We combined a special fixation method with a unique volumetric nondestructive imaging technique and image processing tools to separate individual acini in the mouse lung. Interior scans of the parenchyma at a resolution of 2 µm enabled the reconstruction and quantitative study of whole acini by image analysis and stereologic methods, yielding data characterizing the 3D morphometry of the pulmonary acinus. The 3D reconstructions compared well with the architecture of silicon rubber casts of mouse acini. The image-based segmentation of individual acini allowed the computation of acinar volume and surface area, as well as estimation of the number of alveoli per acinus using stereologic methods. The acinar morphometry of male C57BL/6 mice age 12 wk and 91 wk was compared. Significant increases in all parameters as a function of age suggest a continuous change of the lung morphometry, with an increase in alveoli beyond what has been previously viewed as the maturation phase of the animals. Our image analysis methods open up opportunities for defining and quantitatively assessing the acinar structure in healthy and diseased lungs. The methods applied here to mice can be adjusted for the study of similarly prepared human lungs.

Based on the experimentally determined microstructure of a lithium ion battery (LIB) cathode electrode using X-ray nano-CT technology, a three dimensional simulation framework of galvanostatic discharge with finite volume method is presented. The tomography data were used to evaluate the homogeneity of porosity and tortuosity of the electrode. With this approach, galvanostatic discharge processes at different C rates were simulated and the local effects in the LIB cathode electrode during discharge processes were investigated. The spatial distribution of physical and electrochemical properties in the microsturcture of the cathode electrode, such as concentration, current density, open circuit potential (OCP), overpotential and intercalation reaction rate was revealed in this paper. The simulation results show that the distributions of those properties are very different from the results based on the pseudo two dimensional model. The physical and electrochemical properties distribute in a wider range due to the structure inhomogeneity, which may have a negative impact on LIB performance, especially at large discharge rates.Rechargeable lithium-ion batteries (LIBs) have dominated the power source market for portable electronic devices for many years. Recently, they have attracted a lot of interests in automobile applications due to their relatively high energy and power densities. For instance, LIBs have been used in electric (Nissan Leaf) or plug-in hybrid electric cars (Chevy Volt). However, significant challenges still exist in LIBs, such as capacity fade, unpredicted safety issues, and fast charging. In order to improve battery performance, a lot of effort has been done toward the development of new anode and cathode materials. 1-4 Besides the electrode material properties, the structure of electrodes also plays a critical role in determining the performance of a LIB. 5,6 The microstructure of the active materials forms the boundary for the physical and electrochemical processes within the electrode, such as lithium ion transportation, heat generation, side reactions, phase transformation, and inner stresses. The response of LIBs could be determined by the electrode microstructure especially in the application of high energy and power densities. 7 In order to address the challenges and design better LIB electrodes, fundamental understandings of the physical and electrochemical processes inside a battery during charge and discharge processes are necessary.Mathematical modeling and numerical simulation have been proven to be effective ways to reveal both global and local phenomena that occur in LIB electrodes. Combined with experimental validations, they can give valuable insights into the principles of the LIB performance. To this end, comprehensive mathematical models and variant numerical methods have been developed to simulate the behavior of LIBs and reveal the effect of the microstructure on the performance of LIBs. For instance, Doyle et al. developed a mean field method which incorporates the electrode mi...