Microfluidic ratio metering devices fabricated in PMMA by CO2 laser

Abstract

We describe microfluidic fabrication results achieved using a 10.6 μm CO2 engraving laser on cast PMMA, in both raster and vector mode, with a 1.5″ lens and a High Power Density Focussing Optics lens. Raster written channels show a flatter base and are more U-shaped, while vector written channels are V shaped. Cross-sectional images, and, where possible, stylus profilometry results are presented. The sides of V-grooves become increasing steep with laser power, but broader shallower channels may be produced in vector mode by laser defocus, as illustrated. Smoothing of raster engraved channels by heated IPA etch, and transparency enhancement by CHCl3 vapour treatment are briefly discussed. An asymmetric Y meter is discussed as one method of diluting acid into seawater for dissolved CO2 analysis. Alternatively, microfluidic snake channel restrictors of different lengths in 2 channels may achieve the same result. Samples are fabricated with bases bonded by CHCl3 vapour treatment, and the devices are flow tested with either dilute food dye or DI water. Microfluidics fabricated in this manner have applications in ocean sensing of dissolved CO2 and other analytes, as well as broader sensing measurements, including biomedical sensors.

A Low-Cost 3-in-1 3D Printer as a Tool for the Fabrication of Flow-Through Channels of Microfluidic Systems

“…To test option (1), the microfluidic target was directly milled with the rotating 0.5 mm drill bits into a 3 mm thick tailored PMMA sheet to create a shallow groove that can function as a microchannel. Following literature recommendations [ 33 ], key operational parameters were a spindle speed of 12,000 rpm, cutting feed rate 300 mm/min and plunge rate 36 mm/min. Directly milled PMMA chips with microchannels, hereafter referred to as ‘D-CNC’ chips, were assembled in the custom chip holder with equal-sized flat PDMS sheets to form the functional microfluidic unit.…”

“…For functional tests completed M-CNC PDMS chips were sealed with equally sized solid PMMA substrates and assembled to form a functional unit, using a custom chip holder. Based on the literature recommendations above [ 33 ], the operational settings used for milling depended on the actual mill bit diameter used. The details are discussed in the next section.…”

“…Individually applied in separate setups, 3D printing, CNC micro-milling and laser engraving have been tested in low-cost basic or in more expensive, technically advanced devices in fabricating microfluidic devices and shown to be viable alternatives to conventional photolithography [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. CO 2 laser-based fabrication of microfluidic substrates has, for example, been performed with common materials such as glass and poly methylmethacrylate (PMMA) sheets and the influence of the laser settings and the length and strength of surface treatments on the production of optimal microchannel profiles and on surface smoothness was demonstrated [ 32 , 33 ]. Applications of laser-fabricated microfluidic devices include droplet digital polymerase chain reaction (PCR) [ 34 ], droplet generation [ 35 ], wicking speed modulation on paper microfluidic devices [ 36 ] and culturing of embryonic bodies [ 37 ].…”

Microfluidics in High-Throughput Drug Screening: Organ-on-a-Chip and C. elegans-Based Innovations

“…PMMA is non-cytotoxic, inexpensive, and, like PDMS, transparent, allowing for real-time observation of the chip inside under a microscope [57]. However, in the case of PMMA, chips cannot be fabricated in the same way as soft-lithography, but are generally fabricated by processing PMMA into the desired shape by injection molding [58], laser cutting [59], milling [60], and engraving [61].…”

Craft-and-Stick Xurographic Manufacturing of Integrated Microfluidic Electrochemical Sensing Platform

“…The vigorous milling and high-energy ablation process are effective for the manufacture of fluidic devices with robust materials such as glass [ 15 , 16 ], silicon [ 17 ], and polymers (i.e., PDMS, PMMA) [ 18 , 19 ], while the process may create surface defects for temperature sensitive, thin and fragile substrates. Laser processing, including CO 2 lasers and UV lasers, uses high energy to craft and create patterns on various hard substrates such as glass, borosilicate, silica, and quartz [ 20 ], and a few temperature-resisted polymer substrates [ 21 , 22 ]. However, the high-energy laser cutting process may not be suitable for temperature-sensitive polymer substrates or fire-catching cellulose or paper substrates resulting in a poor quality final product due to the melting, burning, and vaporization of substrate materials [ 23 , 24 ].…”