The centrifugal microfluidic technology is based on utilizing pseudo forces (the centrifugal, Euler and Coriolis forces) generated from spinning a microfluidic disc/CD to displace liquids and automate bioanalytical assays. Several advantages of the centrifugal microfluidic discs in comparison to the stationary lab-on-a-chip platforms include the low cost of a spindle motor used for liquid manipulation, the removing of the air bubbles during disc spinning, and the parallel running of several similar bioassays on a single disc. However, the laminar flow regime in miniaturized microchambers/channels in centrifugal microfluidic discs limits the homogenization process of reagents to slow diffusion. The implementation of 3D geometrical patterns (flow barriers) in microchambers is a well-known approach for disturbing the laminar flow to accelerate liquid mixing in microfluidic platforms. However, the conventional fabrication of the 3D patterns through 3D printing and photolithography are time-consuming, complex and expensive¹.

Recently, we have introduced origami CDs that are made of a conventional laminating film, and by a cutter plotter and laminating machine. Compared to the previous CD microfluidic platforms, the fabrication protocol of an origami CD prevents the need for using bulky and expensive CNC machines, the expensive double-sided adhesive films and the tedious alignment of the disc layers². Therefore, the origami disc fabrication is ideal for the development and low-volume manufacturing of bioanalytical microfluidic discs at extreme point of care (ePOC) settings. To overcome the slow diffusional mixing in origami CDs, in this study, we are introducing a novel approach for making 3D mixing patterns in microchannels/chambers to accelerate homogenization process of reagents that is required for an efficient bioreaction. We employed the blade of the cutter plotter that is used for cutting the origami discs to engrave various pattern designs on mixing chambers. We fabricated mixing chambers equipped with latex microballoons³, and various 3D mixing patterns. Afterwards, we compared the homogenization progress of a colored and colorless liquid in chambers with and without 3D mixing patterns. The results show that in general 3D patterns accelerate the homogenization process of the liquids when compared to the control chambers with no mixing pattern, and patterns that are perpendicular to the reciprocational flow provide the highest mixing efficiency. In general, the engraving of 3D mixing patterns by a cutter plotter is an ideal alternative to the expensive and complex fabrication of similar mixing patterns using 3D printing and photolithography procedures.

References

1. Hou, X. et al. Interplay between materials and microfluidics. Nature Reviews Materials 2, (2017).
2. Aeinehvand, M. M. et al. Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves. RSC Adv. 7, 55400–55407 (2017).
3. Aeinehvand, M. M. et al. Biosensing enhancement of dengue virus using microballoon mixers on centrifugal microfluidic platforms. Biosens. Bioelectron. 67, 424–430 (2015).