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 , 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 , while DTJ channel produced droplet diameter of at the same conditions. Moreover, the modified double T-junction (MDTJ) decreases the variation in droplets diameter at the same flow rates by 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 more than the DTJ channel. The uniformity of droplet distribution inside the channel was enhanced by 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 for fabrication. The minimum generated droplet diameter is within with more than droplets per second (at . 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.
Highlights
Droplet-based polymerase chain reaction enables a more precise, sensitive and reproducible target quantification compared to conventional (PCR)
A micro-droplet formation chip for dynamic continuous-flow-based PCR is fabricated by direct write laser technique on Polymethyl methacrylate (PMMA) material. This cheap combination between low cost of fabrication and raw material produces a micro-droplet formation chip for less than 30 cents. As this fabrication technique produced relatively wide channel, which limit miniaturization of the droplets, we introduced a new inlet channel geometry which may produce small droplet size relative to the channel size
The fabrication was done by a universal laser direct writing machine and using PMMA material as substrate
Summary
Droplet-based polymerase chain reaction (dPCR) enables a more precise, sensitive and reproducible target quantification compared to conventional (PCR). As in those applications if the mutation is less than 3%, it cannot be detected by traditional PCR [4,5] This combination problem could be solved by introducing a low-cost micro-droplet formation chip to make the sample separate into a large number of small partitions and the reaction is carried out in each partition individually [6,7,8,9]. This separation allows a more reliable collection and sensitive quantification of nucleic acid signals [10]. These special behaviors can improve efficiency and decrease cost of reagents and chemical waste [11,12,13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
