CO2 Laser Fabrication of PMMA Microfluidic Double T-Junction Device with Modified Inlet-Angle for Cost-Effective PCR Application

Abstract

The formation of uniform droplets and the control of their size, shape and monodispersity are of utmost importance in droplet-based microfluidic systems. The size of the droplets is precisely tuned by the channel geometry, the surface interfacial tension, the shear force and fluid velocity. In addition, the fabrication technique and selection of materials are essential to reduce the fabrication cost and time. In this paper, for reducing the fabrication cost Polymethyl methacrylate (PMMA) sheet is used with direct write laser technique by VERSA CO2 laser VLS3.5. This laser writing technique gives minimum channel width of about 160 μm, which limit miniaturizing the droplet. To overcome this, modification on double T-junction (DTJ) channel geometry has been done by modifying the channel inlets angles. First, a two-dimensional (2D) simulation has been done to study the effect of the new channel geometry modification on droplet size, droplets distribution inside the channel, and its throughput. The fabricated modified DTJ gives the minimum droplet diameter of 39±2 μm, while DTJ channel produced droplet diameter of 48±4 μm at the same conditions. Moreover, the modified double T-junction (MDTJ) decreases the variation in droplets diameter at the same flow rates by 4.5–13% than DTJ. This low variation in the droplet diameter is suitable for repeatability of the DNA detection results. The MDTJ also enhanced the droplet generation frequency by 8–25% more than the DTJ channel. The uniformity of droplet distribution inside the channel was enhanced by 3–20% compared to the DTJ channel geometry. This fabrication technique eliminates the need for a photomask and cleanroom environment in addition shortening the cost and time. It takes only 20 min for fabrication. The minimum generated droplet diameter is within 40 μm with more than 1000 droplets per second (at 10 mL/normalh. oil flow rate). The device is a high-throughput and low-cost micro-droplet formation aimed to be as a front-end to a dynamic droplet digital PCR (ddPCR) platform for use in resource-limited environment.

Numerical Investigations on Alternate Droplet Formation in Microfluidic Devices

“…But this wouldn't affect the result significantly and would not make the results unreliable. The droplet break-up mechanism in 2D simulations resemble with that of 3D simulation (Leshansky and Pismen 2009) and in relevance to this, many studies in the past (Liu and Zhang 2009; Amaya-Bower and Lee 2011) and recently (Wojnicki et al 2018;Nasser et al 2019) have validated their 2D simulations with an experiment. The results are in good agreement.…”

Basic Guide to Multilayer Microfluidic Fabrication with Polyimide Tape and Diode Laser

“…The fabrication of multilayer microfluidic devices has used conventional photolithography [ 15 ] as well as alternative methods, such as micro-milling [ 11 , 13 , 16 , 17 ] and resin 3-dimensional (3D) printing [ 14 ]. However, direct laser fabrication methods, although widely used for microfluidic fabrication owing to their cost-effectiveness and ease of operation [ 18 , 19 , 20 , 21 , 22 ], have not been extensively explored for use in multilayer microfluidic fabrication.…”

Rapid Prototyping of High-resolution Large Format Microfluidic Device Through Maskless Image Guided In-situ Photopolymerization

“…For example, wax-printing is one of the cheapest fabricating methods that can print ~50 µm features 25 while on the other side of the spectrum, EBL can print features as small as 10 nm but costs ~100,000-1,000,000 USD 26 . Most of the one step direct device or mold fabrication methods are based on mechanical micromachining or laser ablation which result in inferior feature size and significant roughness both in the side wall and the substrate as well as reduced opacity 27 .…”