Effect of the inclined angle of micromilling tool on the fabrication of the microfluidic channel

Micromilling is a common processing method for fabricating microfluidic chips or other microproducts with high processing accuracy and low cost, which is suitable for mass production. The main concern of micromilling is the surface roughness of the work material. However, only a small range of surface roughness can be obtained in the general study of micromilling by changing the processing parameters, which is very difficult to obtain a specific roughness. In the process of micromilling with end mills, due to the structural characteristics of the tool tip, the inclination angle of the tool has a significant impact on the bottom surface of the machined channels. In this work, the influence of the tool inclination on the surface roughness was studied through the inclined micromilling tests of the poly(methyl methacrylate) (PMMA) surface, and it was proposed to realize the control of the machined surface roughness by inclined micromilling. In addition, a theoretical model considering tool inclination was established to calculate the surface roughness of the machined bottom obtained by inclined micromilling. The experimental results were consistent with the theoretical results under the low speeds. Afterwards, the polydimethylsiloxane (PDMS) was used to replicate the microchannel machined on the PMMA surface, and the microfluidic chips were prepared to control the fluid flow in the channel by adjusting the roughness of the bottom of the channel. Results indicated that the smoother channel flowed first under the same flow pressure. The study offers a new idea of surface roughness control, which can be applied to flow control in microfluidic chips.