Dual phononic and photonic band gaps in a periodic array of pillars deposited on a thin plate

We study theoretically the simultaneous existence of phononic and photonic band gaps in a periodic array of silicon pillars deposited on a homogeneous thin silica plate. Several lattices, namely, square, triangular, and honeycomb are investigated for a wide range of geometrical parameters. We discuss the most suitable cases for dual phononic-photonic band gaps, especially in comparison to the more conventional structures constituted by a periodic array of holes in a membrane

Acoustic channel drop tunneling in a phononic crystal

International audienceWe study both theoretically and experimentally the possibility of resonant tunneling of acoustic waves between two parallel guides created in a phononic crystal composed of steel cylinders in water. In the absolute bandgap of the phononic crystal, ranging from 250 to 325 kHz, a full transmission band exits for propagation inside a straight wave guide. We show that the transfer of a particular wavelength can occur between two parallel wave guides coupled together through an appropriate coupling structure. The latter is composed of isolated cavities interacting with stubs located at the sides of the wave guides

Theoretical and experimental evidence of level repulsion states and evanescent modes in sonic crystal stubbed waveguides

The complex band structures calculated using the Extended Plane Wave Expansion (EPWE) reveal the presence of evanescent modes in periodic systems, never predicted by the classical \omega(\vec{k}) methods, providing novel interpretations of several phenomena as well as a complete picture of the system. In this work we theoretically and experimentally observe that in the ranges of frequencies where a deaf band is traditionally predicted, an evanescent mode with the excitable symmetry appears changing drastically the interpretation of the transmission properties. On the other hand, the simplicity of the sonic crystals in which only the longitudinal polarization can be excited, is used to interpret, without loss of generality, the level repulsion between symmetric and antisymmetric bands in sonic crystals as the presence of an evanescent mode connecting both repelled bands. These evanescent modes, obtained using EPWE, explain both the attenuation produced in this range of frequencies and the transfer of symmetry from one band to the other in good agreement with both experimental results and multiple scattering predictions. Thus, the evanescent properties of the periodic system have been revealed necessary for the design of new acoustic and electromagnetic applications based on periodicity

Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics

We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 102 S/cm has been achieved from the demonstrated 3D printable composite with 1.9 vol. % loading of silver nanowires. Utilizing the high conductivity of the printable composites, 3D printing of designed battery electrode pastes is demonstrated. Rheology study shows superior printability of the electrode pastes aided by the cellulose\u27s strong thixotropic rheology. The designed anode, electrolyte, and cathode pastes are sequentially printed to form a three-layered lithium battery for the demonstration of a charging profile. This study opens opportunities of 3D printable conductive materials to create printed electronics with the next generation additive manufacturing process

Caenorhabditis elegans SMA-10/LRIG Is a Conserved Transmembrane Protein that Enhances Bone Morphogenetic Protein Signaling

Bone morphogenetic protein (BMP) pathways control an array of developmental and homeostatic events, and must themselves be exquisitely controlled. Here, we identify Caenorhabditis elegans SMA-10 as a positive extracellular regulator of BMP–like receptor signaling. SMA-10 acts genetically in a BMP–like (Sma/Mab) pathway between the ligand DBL-1 and its receptors SMA-6 and DAF-4. We cloned sma-10 and show that it has fifteen leucine-rich repeats and three immunoglobulin-like domains, hallmarks of an LRIG subfamily of transmembrane proteins. SMA-10 is required in the hypodermis, where the core Sma/Mab signaling components function. We demonstrate functional conservation of LRIGs by rescuing sma-10(lf) animals with the Drosophila ortholog lambik, showing that SMA-10 physically binds the DBL-1 receptors SMA-6 and DAF-4 and enhances signaling in vitro. This interaction is evolutionarily conserved, evidenced by LRIG1 binding to vertebrate receptors. We propose a new role for LRIG family members: the positive regulation of BMP signaling by binding both Type I and Type II receptors

Hypersonic phononic crystal for surface acoustic waves

International audienceA phononic crystal exhibiting a band gap in the near-gigahertz frequency range for surface acoustic waves was fabricated in a lithium niobate substrate. Reflection and transmission properties of the sample were characterized both electrically and optically, by means of embedded broadband interdigitated transducers and optical heterodyne interferometry, respectively. Measurements performed for (XZ) propagating surface waves show the existence of a band gap between 660 and 900 MHz. Optical measurements confirm that the phononic crystal behaves as a perfect mirror for waves propagating at frequencies within the band gap. Outside of the band gap, transmission can be observed for frequencies below, but also above the forbidden frequency range, hence showing that losses experienced by high frequency surface acoustic waves, i.e. for modes located beyond the sound line, can be partially overcome