Glass welding using custom developed femtosecond fiber laser for microfluidic device development

Abstract

Microfluidic chips made of different materials are utilized in numerous examination fields, as they make it possible to screen and study distinctive processes that happen in minuscule sizes. A typical microfluidic device consists of two plates, one with a surface with microstructures, the other covers the top of the channel structures to isolate the assembly from the environment. Many of the traditional methods used to combine these two plates require preliminary preparation, which adds time, cost and energy to production, but the result can still be problematic in terms of repeatability and longevity. In this thesis, it is aimed to produce microchannels on glass samples and to join them together using a femtosecond laser. In this way, application-specific modifications, repeatable and faster chip production may be possible. We have built a femtosecond fiber laser system with adjustable output parameters for the production of microchannels and welding of glasses. The central wavelength of the developed laser is 1030 nm and the pulse duration can be adjusted between 250 fs -10 ps, pulse energy up to 5 μJ and repetition frequency between 150 - 400 kHz independently from each other. Using this fiber laser system, we investigated the most suitable parameters for glass welding. For this, we have built up two experimental setups with scanning systems that can operate at m/s and mm/s speeds. We examined the effects of laser pulse energy, repetition rate and scanning speed for welding of glasses with different thicknesses and types. We have achieved successful results in welding experiments with spiral and raster scanning on borosilicate and aluminosilicate glasses with different thicknesses. Durability tests of the welded glasses were carried out with a press test machine and preliminary results for microfluidic device development were presented.