FRANCESCO VENTURINI¹*, MAURIZIO SANSOTERA¹, ROBERTO OSELLAME², GIULIO CERULLO², WALTER NAVARRINI¹
*Corresponding author
1. Politecnico di Milano Dipartimento di Chimica, Materiali e Ingegneria Chimica”Giulio Natta”, Via Luigi Mancinelli, 7, Milan, 20133, Italy
2. Politecnico di Milano, Istituto di Fotonica e Nanotecnologie – CNR, Dipartimento di Fisica – Piazza Leonardo da Vinci, 32, Milan, 20133, Italy

Abstract

Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica.
The procedure attested in literature, which has been widely studied in the past years, consists of irradiating a glass slab and subsequently apply a chemical etching step. The results obtained by different research groups vary widely. In this paper we present a review of the most recent advancements of this technique discussing several critical factors that affect the aspect ratio, the length and the etching speed of the microchannel.

INTRODUCTION

Microfluidic devices are interesting tools for synthetic chemistry and analysis: micro-reactors (μR) are proven to be extremely useful when dealing with unstable intermediates or with extremely fast exothermic reactions like oxidations or fluorinations with elemental fluorine (1-3). Micro total analysis systems (μ-TAS) offers the capabilities of preparation, transport, reaction, and analysis of very small volumes of biological samples. This is possible by squeezing onto a single substrate the functionalities of a biological laboratory (4, 5).
The microfeatures are embedded mainly onto three class of materials: metal, ceramics, glass / silicon or polymers. The choice of the material is basically due to the characteristics of the chemicals that will be fluxed inside the microdevices. Inorganic fluorides require metals microdevices, organic chemicals and water based solutions are better handled with glass devices while polymer engraved microdevices are used because of their mechanical flexibility and surface energy tuning (6-8). Any material used in the microfabrication require its own specific machining technique.
Glass is th ...