Anodic bonding of mid-infrared transparent germanate glasses for high pressure - high temperature microfluidic applications

Julien Ari (1, 2) , Geoffrey Louvet (1, 2) , Yannick Ledemi (2) , Fabrice Célarié (3) , Sandy Morais (4) , Bruno Bureau (1) , Samuel Marre (4) , Virginie Nazabal (1) , Younès Messaddeq (2)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 ULaval - Université Laval [Québec]
3 IPR - Institut de Physique de Rennes
4 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

High pressure/high-temperature microreactors based on silicon-Pyrex® microfabrication technologies have attracted increasing interest in various applications providing optical access in high-pressure flow processes. However, they cannot be coupled to infrared spectroscopy due to the limited optical transparency (up to ~2.7 μm in the infrared region) of the Pyrex® glass substrate employed in the microreactor fabrication. To address this limitation, the alternative approach proposed in this work consists in replacing the Pyrex® glass in the microreactor by a mid-infrared transparent glass with thermal and mechanical properties as close as possible or even better to those of the Pyrex®, including its ability for silicon-wafers coupling by the anodic bonding process. Glasses based on germanate GeO2, known for their excellent transmission in the mid-infrared range and thermal/thermo-mechanical properties, have been thus evaluated and developed for this purpose. The optical, mechanical, thermal and electrical conductivity properties of adapted glass compositions belonging to five vitreous systems have been systemically investigated. The glass composition 70GeO2-15Al2O3-10La2O3-5Na2O (mol.%) was defined as the best candidate and produced in large plates of 50 mm diameter and 1 mm thickness. Anodic bonding tests with Si-wafers have been then successfully conducted, paving the way for the development of fully mid-infrared transparent silicon-glass microreactors.

Mots clés: Germanate glass; mid-infrared; anodic bonding; high pressure/high temperature; microfluidics; mid- infrared

Domaines: Matériaux; Physique [physics]

Julien Ari, Geoffrey Louvet, Yannick Ledemi, Fabrice Célarié, Sandy Morais, et al.. Anodic bonding of mid-infrared transparent germanate glasses for high pressure - high temperature microfluidic applications. Science and Technology of Advanced Materials, 2020, 21 (1), pp.11-24. ⟨10.1080/14686996.2019.1702861⟩. ⟨hal-02467111⟩