Parrot beak‐inspired metamaterials with friction and interlocking mechanisms 3D/4D printed in micro and macro scales for supreme energy absorption/dissipation

Energy absorption and dissipation features of mechanical metamaterials have widespread applications in everyday life, ranging from absorbing shock impacts to mechanical vibrations. This article proposes novel bioinspired friction-based mechanical metamaterials with a zero Poisson's ratio behavior inspired from parrot's beaks and manufactured additively. The mechanical performances of the corresponding metamaterials are studied at both macro and micro scales by experiments and finite element analysis (FEA). An excellent agreement is observed between the FEA and both microscopic and macroscopic scale experiments, showing the accuracy of the developed digital tool. Performances are compared to traditional triangular lattice metamaterials. Both experimental tests and FEA results demonstrate the following advantages: 1) absorbing and dissipating energy per unit of mass (SEA) at large compressive strains without global buckling; 2) bistable deformation patterns including friction-based and interlocking mechanisms; 3) reversible deformation patterns after unloading; 4) shape recovery behavior after a heating–cooling process; and 5) the higher elastic modulus of micro metamaterials compared with their macro counterparts. This is the first demonstration of a bioinspired friction-based design of 3D-printed mechanical metamaterials that feature absorbing/dissipating energy, stability, and reversibility properties to cater to a wide range of sustainable meta-cylinders in micro and macro scales

Fabrication collective de cristaux photoniques LiNbO3

International audienc

Batch process for the fabrication of LiNbO3 photonic crystals using proton exchange followed by CHF3 reactive ion etching

International audienceWe report a simple process for the batch fabrication of photonic crystals in lithium niobate substrates. By means of proton-exchange (PE) followed by CHF3 reactive ion etching (RIE) we have achieved structures with a diameter of 400 nm and an aspect ratio (depth-to-diameter) of 3:1. Sub-micrometric structures have been fabricated with an 85 degrees angle between the walls and the plane of the substrate. We provide the optimized parameters - and their influence on the aspect ratio, the etching rate and the verticality of the walls. Transversal cross-section micrographs of the etched patterns, for both X-cut and Z-cut substrates, are shown as a clear evidence of the capability developed. (C) 2008 Elsevier B.V. All rights reserved

Etude et réalisation d'une structure à cristaux photoniques en niobate de lithium pour la modulation électro-optique

National audienc

Experimental evidence of enhanced electro-optic control on a lithium niobate photonic crystal superprism

International audienceWe present experimental evidence of an electro-optic superprism photonic crystal fabricated on a lithium niobate substrate, in agreement with simulation results. In this work, rather than changing the incident wavelength or angle to achieve large light deflections, a direct modification of the band structure by the electro-optic effect causes changes in the propagation direction of the incident beam. Additionally, the chosen geometry allows significant ultrarefraction as the incident wavelength is varied giving rise to a double purpose active-passive photonic crystal light deflector that could present potential interest for optical communication

Acoustic wave filter based on periodically poled lithium niobate

International audienceSolutions for the development of compact RF passive transducers as an alternative to standard surface or bulk acoustic wave devices are receiving increasing interest. This article presents results on the development of an acoustic band-pass filter based on periodically poled ferroelectric domains in lithium niobate. The fabrication of periodically poled transducers (PPTs) operating in the range of 20 to 650 MHz has been achieved on 3-in (76.2-mm) 500-μm-thick wafers. This kind of transducer is able to excite elliptical as well as longitudinal modes, yielding phase velocities of about 3800 and 6500 ms(-1), respectively. A new type of acoustic band-pass filter is proposed, based on the use of PPTs instead of the SAWs excited by classical interdigital transducers. The design and the fabrication of such a filter are presented, as well as experimental measurements of its electrical response and transfer function. The feasibility of such a PPT-based filter is thereby demonstrated and the limitations of this method are discussed