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A microfluidic radial diffuser typically comprises a hole in a membrane facing a concentric pillar separated by a small gap where the fluid is forced to flow radially between the membrane and the pillar. Such diffusers are notably used to make passive flow rectification valves for drug delivery devices, wherein several holes are machined into a flexible membrane progressively deflecting against pillars as the pressure increases on top of it. The fluidic modelling of such a diffuser is made difficult by the presence of a transition region between the hole and the diffuser itself. An experimental investigation has been conducted using SOI wafers to form membranes having only one central hole and Pyrex wafers for the substrate and pillars. Both wafers are anodically bonded together after alignment. A simple fluidic model accounting for the specific geometry of the diffuser is proposed and compared to experimental results. A good match is obtained, for Reynolds number in the range 0.5 to 35, using the analytical formula of a radial diffuser in the laminar regime with an effective inner radius 40% smaller than the actual one, in order to correctly simulate the flow constriction at the entrance of the diffuser.

Flow control valves comprise a silicon flexible membrane that deflects against a substrate, usually made of glass, containing pillars, an outlet hole, and anti-stiction features. However, there is a strong interest in using silicon instead of glass as substrate material, as it would simplify the process flow by allowing the use of well controlled anisotropic etching. Moreover, specific devices demanding a bending of the substrate would also benefit from the inherent outstanding mechanical strength of monocrystalline silicon. Unfortunately, direct Si-Si bonding is not easily achieved with highly structured wafers since residual stress may prevent the good adhesion between wafers. Using a thermoplastic polymer, such as parylene, as intermediate layer is not well adapted to this design as the wafer-to-wafer alignment is critical. An alternative anodic bonding method using an intermediate borosilicate layer has been successfully tested. This layer has been deposited onto the silicon substrate. The bonding recipe has been adapted to account for the presence of the SOI buried oxide and intermediate glass layer in order not to exceed the breakdown voltage. Flow control valves dedicated to infusion of viscous fluids at very high pressure have been made and characterized. The results are compared to previous data obtained using the standard anodic bonding method., {"references":["X. Zhang, N. Xiang, W. Tang, D. Huang, X. Wang, H. Yi, Z. Ni, \"A passive flow regulator with low threshold pressure for high-throughput inertial isolation of microbeads,\" Lab Chip, vol. 15(17), pp. 3473-3480, 2015.","E. Chappel, D. Dumont-Fillon, S. Mefti, \"Passive flow regulators for drug delivery and hydrocephalus treatment,\" in Proc. SPIE 8976 Microfluidics, BioMEMS, and Medical Microsystems XII, San Francisco, USA, 2014, paper 89760S.","E. Chappel, \"Adjustable passive flow regulator,\" European Patent EP2943708B1, 2017.","J. Leib, U. Hansen, S. Maus, H. Feindt, K. Hauck, K. Zoschke, M. Toepper, \"Anodic bonding at low voltage using microstructured borosilicate glass thin-films,\" Proc. Electronic System-Integration Technology Conf. (ESTC) 3rd, Berlin, Germany, 2010, pp. 1-4.","D. Dumont-Fillon, M. Hannebelle, H. van Lintel, E. Chappel, \"Design of a Passive Flow Regulator Using a Genetic Algorithm,\" in Proc. 30th Eurosensors Conf., Budapest, Hungary, 2016, Procedia Engineering vol.168, pp 1016-1019.","A. Hanneborg, M. Nese, P. Ohlckers, \"Silicon-to-silicon anodic bonding with a borosilicate glass layer,\" J. Micromech. Microeng., vol. 1(3), pp. 139–144, 1991.","M. Esashi, A. Nakano, S. Shoji, H. Hebiguchi, \"Low-temperature silicon-to-silicon anodic bonding with intermediate low melting point glan,\" Sensors Actuators A. Phys., vol. 23(1–3), pp. 931–934, 1990.","W.-B. Choi, B.-K Ju, Y.-H. Lee, J.-W. Jeong, M. R. Haskard, N.-Y Lee, M.-Y. Sung, M.-H Oh, \"Experimental analysis on the anodic bonding with an evaporated glass layer,\" J. Micromech. Microeng., vol. 7, pp. 316-322, 1997.","F. Koliatene, \"Contribution à l'étude de l'existence des décharges dans les systèmes de l'avionique,\" PhD Thesis, University of Toulouse III, France, 5 janvier 2009.\n[10]\tS. Weichel, R. de Reus, M. Lindahl, \"Silicon-to-silicon wafer bonding using evaporated glass,\" Sensors and Actuators A-Phys., vol. 70(1-2), pp. 179–184, 1998.\n[11]\tE. Tatar, M. M. Torunbalci, S. E. Alper, T. Akin, \"A method and electrical model for the anodic bonding of SOI and glass wafers,\" Proc. MEMS 2012, Paris, France, 2012, pp. 68-71. \n[12]\tL. Cornaggia, L. Conti, M. Hannebelle, S. Gamper, D. Dumont-Fillon, H. van Lintel, P. Renaud, E. Chappel, \"Passive flow control valve for protein delivery,\" Cogent Engineering, 1413923, 2017."]}

We present a study of the magnetic properties of layered oxides that belong to the AMO2 family (A=Li, Na; M=Ni, Fe, Co). The compounds are very promising materials for battery applications. LiNiO2 is the subject of strong theoretical interest due to the possible coupling between spin and orbital degrees of freedom. Several works have been devoted to the magnetic properties of LiNiO2 but the results remain much debated. Since this is also crucial for battery capacity, solid state chemists have improved the synthesis and the characterisation of the samples these last years. It has been shown that both electrochemical and magnetic properties are very sensitive to the departure from the stoichiometry. The magnetic properties of the perfectly lamellar NaNiO2 system have been first studied by means of electron spin resonance, neutron diffraction, high field magnetization and low field susceptibility. NaNiO2 is an A-type antiferromagnetic insulator with a ferrodistorsive orbital ordering for T, Ce mémoire de thèse présente une étude des propriétés magnétiques de quelques oxydes lamellaires de la famille AMO2 (A=Li, Na; M=Ni, Fe, Co). Ces composés sont notamment utilisés en tant que matériaux pour électrodes positives dans les batteries lithium-ion. Les propriétés magnétiques de LiNiO2 avaient déjà fait l'objet de nombreuses études mais la grande disparité des résultats obtenus n'avait permis de dégager aucun consensus quant à la nature de son état fondamental. Le rôle joué par les degrés de liberté orbitaux sur la frustration magnétique est notamment fortement débattu. Afin d'améliorer les performances des batteries, les chimistes du solide ont de leur côté considérablement amélioré les conditions de synthèse et de caractérisations physico-chimiques au cours de ces dernières années. Il s'est révélé que l'écart à la stœchiométrie des matériaux étudiés avait des conséquences dramatiques à la fois sur les propriétés magnétiques et électrochimiques. Dans un premier temps, une étude complète des propriétés magnétiques et structurales du composé stœchiométrique NaNiO2 est présentée. Les techniques expérimentales utilisées sont la résonance électronique de spin, la diffraction neutronique, les mesures d'aimantation à hauts champs et de susceptibilité en champs faibles. NaNiO2 est un AF de type A qui présente un ordre orbital de type Ferro pour T

Diabetes is a chronic condition that occurs when the pancreas does not produce enough insulin or when the body cannot effectively use the insulin it produces. People having type 1 diabetes require insulin (10% of all diabetics). People with type 2 diabetes can be treated with oral medication, but may also require insulin; 10% of all type 2 diabetics require insulin. Among the actual different methods to administer insulin (syringes, pens and conventional infusion pumps) a possibility to increase infuser performances is offered by the utilization of silicon based MEMS pumps (Micro- Electro Mechanical Systems). The main two pump families are classified as mechanical and non-mechanical pumps. The former contains check-valve, peristaltic, rectification without valves and rotary ones (“Displacement Pumps”) or Ultrasonic and Centrifugal (“Dynamic Pumps”); the latter consists in Pressure, Concentration, Electrical Potential gradients and Magnetic Potential micro-pumps. The micro-pump described here is an electro-mechanical device actuated with a piezoelectric-element and based on MEMS technology, able to minimize size and costs, offering a high precision pharmacological dispense. Three slices are bonded to reach the final results: top and bottom caps and an intermediate SOI. In case of anodic bonding, top and bottom caps are constituted of micromachined borophosphosilicate wafers, whereas in case of metallic bonding three silicon slices are used. The paper deals with the fabrication evolution of the device according to the different items that had to be faced during development: design, fluidic, mechanical and electrical simulations and characterization, safety requirements and final testing. Built-in reliability is ensured by two inner sensors able to detect any occlusion or malfunctioning and informing so the patient. The result is a compact, core pump chip that can deliver from 0.02 Units of insulin up to 3.6 Units per minute with accuracy better than 5%.