Experimental approach to the laser machining of PMMA substrates for the fabrication of microfluidic devices

This paper deals with CO2 laser machining of a suitable amorphous polymer (PMMA) as a flexible technique for the rapid fabrication of miniaturized structures such as microfluidic devices.A model to estimate the main dimensions (depth and width) of the grooves produced by the laser on PMMA is presented, taking into account the influence of the main process parameters (incident power, scanning speed and spot diameter). This theoretical model allows to control the engraving process showing that laser could represent a valid alternative for the production of microchannels. PMMA single-use devices are found to be easier to manufacture with respect to the conventional glass or silicon products.In a second step, IR laser vaporization is adopted for the removal of a single layer of PMMA. This is achieved using multiple overlapping sequences of straight grooves with different scanning directions. The proposed technique showed that the removal depth varied proportionally with the number of layers machined, while surface roughness is influenced by the grooves spacing and the orientation of the scanning direction between successive layers.A method for thermally bonding the PMMA sheets, constituting the 3D structure of the chip, is also presented. The combination of high temperatures and low bonding pressures makes it possible to generate a bulk junction enabling good performances in terms of sealing characteristics.

Research Highlights
► CO2 laser machining of PMMA for the fabrication of microfluidic devices.
► Model to estimate the dimensions of the grooves profile using incident power, scanning speed and spot diameter.
► IR laser vaporization of multiple overlapping grooves with different scanning directions.
► Layer by layer technique to engrave PMMA.
► Method for thermally bonding the PMMA sheets by combination of high temperatures and low bonding pressures.