Polymer Microchannel and Micromold Surface Polishing for Rapid, Low-Quantity Polydimethylsiloxane and Thermoplastic Microfluidic Device Fabrication

Abstract

Polymer-based micromolding has been proposed as an alternative to SU-8 micromolding for microfluidic chip fabrication. However, surface defects such as milling marks may result in rough microchannels and micromolds, limiting microfluidic device performance. Therefore, we use chemical and mechanical methods for polishing polymer microchannels and micromolds. In addition, we evaluated their performance in terms of removing the machining (milling) marks on polymer microchannel and micromold surfaces. For chemical polishing, we use solvent evaporation to polish the sample surfaces. For mechanical polishing, wool felt polishing bits with an abrasive agent were employed to polish the sample surfaces. Chemical polishing reduced surface roughness from 0.38 μm (0 min, after milling) to 0.13 μm after 6 min of evaporation time. Mechanical polishing reduced surface roughness from 0.38 to 0.165 μm (optimal pressing length: 0.3 mm). As polishing causes abrasion, we evaluated sample geometry loss after polishing. Mechanically and chemically polished micromolds had optimal micromold distortion percentages of 1.01% ± 0.76% and 1.10% ± 0.80%, respectively. Compared to chemical polishing, mechanical polishing could better maintain the geometric integrity since it is locally polished by computer numerical control (CNC) miller. Using these surface polishing methods with optimized parameters, polymer micromolds and microchannels can be rapidly produced for polydimethylsiloxane (PDMS) casting and thermoplastic hot embossing. In addition, low-quantity (15 times) polymer microchannel replication is demonstrated in this paper.

A Review of Cyclic Olefin Copolymer Applications in Microfluidics and Microdevices

“…In addition, the lowest value of surface roughness (0.173 µm) was obtained when the following values were chosen: a spindle speed of 20 000 rpm, a feed rate of 300 mm min −1 , and a depth cut of 20 µm. Tsao and Wu [ 131 ] investigated micromachining effects on COC surface roughness. They evaluated the surface roughness after milling at spin speeds ranging from 10 000 to 30 000 rpm and feed rates of 1 to 9 mm s −1 .…”

Rapid prototyping of PMMA-based microfluidic spheroid-on-a-chip models using micromilling and vapour-assisted thermal bonding

“…We showed that this roughness can be mitigated by surface treatment with chloroform vapour. It was previously reported that the use of chloroform, cyclohexane, and acetone for chemical polishing is an effective method to reduce the surface roughness of various machined thermoplastic materials 25 , 26 , 45 , 46 . After exposure to chloroform vapour, we also observed a clear improvement in the surface quality of the micromilled channel.…”

3D-Printed Microfluidic Chip for Real-Time Glucose Monitoring in Liquid Analytes

“…On the other hand, micromolding is a technique for the fabrication of microfluidics in polymers using molds with a negative of the desired geometry. Although micromolding technology requires several steps including the mold preparation, an imprint of polymer material, curing of the polymer, separation, and bonding, it can be utilized in many biomedical applications [ 33 , 34 , 35 ]. In addition, many hybrid fabrication technologies are proposed in the literature to overcome existing drawbacks of the previously mentioned technologies and reduce the price and fabrication time.…”