Rapid prototyping of whole-thermoplastic microfluidics with built-in microvalves using laser ablation and thermal fusion bonding

Recently, there has been an increasing effort in developing new fabrication methods for rapid prototyping of microfluidic chips using thermoplastic materials. This is mainly due to the excellent properties of thermoplastics including inherent robustness to mechanical deformation and resistance to chemicals. In this paper, we report on the development of a novel rapid prototyping method to fabricate microfluidic chips from thermoplastic materials with embedded pneumatic controls. A CO2 laser micromachining method was employed to engrave and cut poly(methyl methacrylate) (PMMA) sheets, which together with a thermoplastic polyurethane (TPU) film, enabled fabrication of various functional microfluidic elements including microvalves, micropumps, and bioreactors. To generate the gas-actuated microvalve, unfocused CO2 laser beam was used to fabricate semi-circular fluid channels in PMMA. An optimized chemical surface treatment procedure was subsequently applied to smoothen the surface of the microchannels. TPU film serving as a flexible membrane was attached above the semi-circular channel sandwiched by another piece of PMMA containing a gas channel to achieve the architecture of the microvalve. A thermal fusion bonding method was developed to bond TPU film to the PMMA components in a single step. A peristaltic micropump was also fabricated consisting of sequential interconnected gas-actuated microvalves. In addition, results from cell cultures in fabricated whole-thermoplastic bioreactors demonstrated biocompatibility of the whole-thermoplastic microchips. Taken together, the developed fabrication process in conjunction with proposed thermoplastic materials provide an inexpensive and versatile method for rapid prototyping of various microfluidic devices.