Introduction: What is a capillary open microsystem?
While most developed microfluidic chips are closed systems equipped with a top plate to cover mechanically and to contact electrically to drop samples, capillary open microsystems are opened systems with a single plate without any electric contact to drops directly. The chips consist of a linear array of patterned electrodes at 1.8 mm pitch was fabricated on a glass plate coated with thin hydrophobic and dielectric layers by using various methods including photolithography, spin coating and ion sputtering. Several actuations such as lateral oscillation, colliding mergence and translational motion for 3–10L water drops have been demonstrated satisfactory. All these kinetic performances of opened chips were similar to those of closed chip systems, indicating superiority of a none-contact method for the transport of drops on opened microfluidic chips actuated by using electro wetting technique (Lee et al., 2018).
Methods: Capillary Open Microsystem Structure
Simultaneously, the upper surface of the emulsification device needed to completely repel both water and oil, in order to confine these liquids within the wettable channel. This implied that the upper surface has to be “superomniphobic”, achieving very high contact angles with both water and oil. All superomniphobic surfaces require the formation of the CassieBaxter state, in which air is entrapped within the rough surface texture beneath the contacting liquid. (Li, Boban, & Tuteja, 2017).
Results: Review of Capillary Open Microsystem
Extension of the capability of low-cost, rapidly produced, open channel microfluidic devices to fabricate hydrophilic microparticles for drug delivery, and potentially the encapsulation of cells within different polymers, both of which are highly desirable within the biological and biomedical fields. Li et al. presented new open channel microfluidic devices based on surfaces with patterned wettability that are capable of controlling the flow of virtually all high and low surface tension liquids. The fabricated open channel devices are capable of constraining a variety of low surface tension oils at high enough flow rates to enable, for the first time, water-in-oil microfluidic emulsification in an open channel device. By changing the flow rates for both the aqueous (dispersed) and organic (continuous) phases, Li et al. showed that it is possible to vary the size of the emulsified droplets produced in the open channel device. Finally, Li et al. utilized the fabricated devices to synthesize relatively monodisperse, hydrogel microparticles that could incorporate a drug molecule. Li et al. also investigated the drug release characteristics of the fabricated particles. C. Li et al. have fabricated the first open-channel microfluidic devices capable of water-in-oil emulsification. This capability was enabled by the localized incorporation of different surfaces with selective wettabilities, including superomniphobic surfaces, and surfaces that are simultaneously hydrophobic and oleophilic. The robust all-liquid repellent, superomniphobic fluoro-paper kept all liquids, including the low-surface-tension outer organic phase, from overflowing from the open fluid channels, even at high flow rates. The hydrophobic and oleophilic sidewalls and floor of the open channels greatly enhanced the flow rate of the continuous organic phase, enabled the emulsification of the aqueous phase, and prevented the aqueous phase from pinning on different areas of the microfluidic device. Li et al. also utilized the fabricated open channel devices for the fabrication of hydrogel based, relatively monodisperse microparticles capable of incorporating a chemotherapy drug molecule – doxorubicin(Li et al., 2017).
Conclusion: Conclusion
Capillary open microsystems are attractive as they allow simple and reliable control of fluid flows. In contrast to closed microfluidic systems, however, two-phase capillary flows in open microfluidics have mainly remained unexplored(Lee et al., 2018). Open microfluidic channels allow the formation of capillary-driven biphasic flows. Key features of open droplet-based microfluidics such as a reduced set of equipment and fabrication requirements and accessibility to the droplets at any point in the channel will be enabling chemistry, biology, and engineering applications. Extension of the capability of low-cost, rapidly produced, open channel microfluidic devices to fabricate hydrophilic microparticles for drug delivery, and potentially the encapsulation of cells within different polymers, both of which are highly desirable within the biological and biomedical fields(Li et al., 2017).
Keywords: Open Microfluidics, Capillary, Microsystems, Biotechnology