Improving surface smoothness of laser-fabricated microchannels for microfluidic application

• Published in: Journal of micromechanics and microengineering Vol. 21; no. 9; pp. 95008 - 8
• Main Authors: WANG, Z. K, ZHENG, H. Y, LIM, R. Y. H, WANG, Z. F, LAM, Y. C
• Format: Journal Article
• Language: English
• Published: Bristol Institute of Physics 01.09.2011
• Subjects: Acetone; Applied fluid mechanics; Applied sciences; Carbon dioxide lasers; Cross-disciplinary physics: materials science; rheology; Etching; Ethyl alcohol; Exact sciences and technology; Fluid dynamics; Fluidics; Fundamental areas of phenomenology (including applications); Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Materials science; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Methods of deposition of films and coatings; film growth and epitaxy; Microchannels; Microfluidics; Micromechanical devices and systems; Physics; Precision engineering, watch making; Surface roughness; Temperature control; Roughness; Solubility; Ultrasonic waves; Rough surfaces; Chemical etching; Hand writing; PMMA; Rapid prototyping; Maskless lithography; Laser ablation technique; Temperature control; Laser assisted process; Smooth surface; Microfluidics; Fluidics
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/21/9/095008

Inexpensive and flexible CO sub(2) laser rapid prototyping of polymer microfluidics is facing challenges due to the rough microchannel surface typically with a roughness Ra in the mu m range produced directly through laser ablation. In this study, a wet chemical etching technique was developed and used successfully to carry out smoothing of microchannel surfaces fabricated on a polymethyl methacrylate substrate using CO sub(2) laser direct writing. The microchannel surface roughness of a few mu m was significantly reduced through etching in acetone diluted with ethanol in an ultrasonic bath in a short time cycle. The surface roughness Ra of below 10 nm could be achieved through etching in the heated etchant solution while without noted deformation in a microchannel structure. The mechanism to reduce surface roughness by the tunable solubility of a polymer in a liquid through concentration and temperature control is discussed with respect to the effect of the etching parameters: acetone concentration, etching time and the temperature of the etching solution. The results would be attractive for microfluidic chip applications when using laser prototyping.