High Repetition Rate UV versus VIS Picosecond Laser Fabrication of 3D Microfluidic Channels Embedded in Photosensitive Glass.

Glass is an alternative solution to polymer for the fabrication of three-dimensional (3D) microfluidic biochips. Femtosecond (fs) lasers are nowadays the most promising tools for transparent glass processing. Specifically, the multiphoton process induced by fs pulses enables fabrication of embedded 3D channels with high precision. The subtractive fabrication process creating 3D hollow structures in glass, known as fs laser-assisted etching (FLAE), is based on selective removal of the laser-modified regions by successive chemical etching in diluted hydrofluoric acid solutions. In this work we demonstrate the possibility to generate embedded hollow channels in photosensitive Foturan glass volume by high repetition rate picosecond (ps) laser-assisted etching (PLAE). In particular, the influence of the critical irradiation doses and etching rates are discussed in comparison of two different wavelengths of ultraviolet (355 nm) and visible (532 nm) ranges. Fast and controlled fabrication of a basic structure composed of an embedded micro-channel connected with two open reservoirs, commonly used in the biochip design, are achieved inside glass. Distinct advantages such as good aspect-ratio, reduced processing time for large areas, and lower fabrication cost are evidenced.