An investigation into the kinematics of magnetically driven droplets on various (super)hydrophobic surfaces and their application to an automated multi-droplet platform
Magnetic actuation on digital microfluidic (DMF) platforms may provide a low-cost, less cumbersome alternative for droplet manipulation in comparison to other techniques such as electrowetting-on-dielectric. Precise control of droplets in magnetically driven DMF platforms is achieved using a low-friction surface, magnetically susceptible material/droplet(s), and an applied magnetic field. Superhydrophobic (SH) surfaces offer limited friction for aqueous media as defined by their high water contact angles (WCA) (>150°) and low sliding angles (<10°). The low surface friction of such coatings and materials significantly reduces the force required for droplet transport. Here, we present a study that examines several actuation parameters including the effects of particle and particle-free actuation mechanisms, porous and non-porous SH materials, surface chemistry, droplet speed/acceleration, and the presence of surface energy traps (SETs) on droplet kinematics. Automated actuation was performed using an XY linear stepper gantry, which enabled sequential droplet actuation, mixing, and undocking operations to be performed in series. The results of this study are applied to a quantitative fluorescence-based DNA assay in under 2 min.
KeywordsMagnetic actuation Superhydrophobic Droplet DNA quantitation
The authors would like to extend their gratitude to Dr. Guojun Liu’s research group at Queen’s University for assisting with contact angle measurements and NanoFabrication Kingston where the laser micromachining was performed. The authors would also like to acknowledge the funding bodies, namely CMC Microsystems for its microfabrication support, the Canadian Foundation for Innovation (emSYSCAN Project) for infrastructure (XY gantry), and Natural Sciences and Engineering Research Council for Discovery Grant Funding.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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- 12.Feng W, Li L, Ueda E, Li J, Heißler S, Welle A, et al. Surface patterning via thiol-yne click chemistry: an extremely fast and versatile approach to superhydrophilic-superhydrophobic micropatterns. Adv Mater Interfaces. 2014;1(7):1400269. https://doi.org/10.1002/admi.201400269.CrossRefGoogle Scholar
- 17.Tenjimbayashi M, Higashi M, Yamazaki T, Takenaka I, Matsubayashi T, Moriya T, et al. Droplet motion control on dynamically hydrophobic patterned surfaces as multifunctional liquid manipulators. ACS Appl Mater Interfaces. 2017;9(12):10371–7. https://doi.org/10.1021/acsami.7b01641.CrossRefPubMedGoogle Scholar
- 18.Bachus K. Engineering patterned materials and microstructured fibers for microfluidics and analytical applications. PhD dissertation. Kigston: Queen’s University; 2017.Google Scholar
- 19.Bachus KJ, Mats L, Choi HW, Gibson GTT, Oleschuk RD. Fabrication of patterned superhydrophobic/hydrophilic substrates by laser micromachining for small volume deposition and droplet-based fluorescence. ACS Appl Mater Interfaces. 2017;9(8):7629–36. https://doi.org/10.1021/acsami.6b16363.CrossRefPubMedGoogle Scholar
- 23.Decrop D, Pardon G, Brancato L, Kil D, Zandi Shafagh R, Kokalj T, et al. Single-step imprinting of femtoliter microwell arrays allows digital bioassays with attomolar limit of detection. ACS Appl Mater Interfaces. 2017;9(12):10418–26. https://doi.org/10.1021/acsami.6b15415.CrossRefPubMedGoogle Scholar
- 26.Mats L. Continuous and digital approaches to manipulation and detection of analytes on microfluidic devices. Queen’s University; 2016.Google Scholar