Open microfluidics
[8][9] Paper-based microfluidics is an attractive method because paper is cheap, easily accessible, and has a low environmental impact.
[11] The application of paper as a diagnostic tool has shown to be powerful because it has successfully been used to detect glucose levels,[12] bacteria,[13] viruses,[14] and other components in whole blood.
[16][17] Lateral flow immunoassays, such as those used in pregnancy tests, are one example of the application of paper for point of care or home-based diagnostics.
[19] Common thread materials include nitrocellulose, rayon, nylon, hemp, wool, polyester, and silk.
[21] Additionally, two or more threads can converge together in a knot bringing two separate ‘streams’ of fluid together as a reagent mixing method.
The dynamics of capillary-driven flow in open microfluidics are highly reliant on two types of geometric channels commonly known as either rectangular U-grooves or triangular V-grooves.
[27] V-grooves with sharp groove angle result in the interface curvature at the corners explained by reduced Concus-Finn conditions.
[5][33] The fabrication of a V-groove is more difficult than a U-groove as it poses a higher risk for faulty construction, since the corner has to be tightly sealed.
[28] One of the main advantages of open microfluidics is ease of accessibility which enables intervention (i.e., for adding or removing reagents) to the flowing liquid in the system.
[1][35] Open microfluidic devices enable better optical transparency because at least one side of the system is not covered by the material which can reduce autofluorescence during imaging.
[37] An example of one of these methods for achieving low flow rates using temperature-controlled evaporation has been described for an open microfluidics system, allowing for long incubation hours for biological applications and requiring small sample volumes.
[38] Open system microfluidics enable surface-tension driven flow in channels thereby eliminating the need for external pumping methods.
These compounds and materials can affect surface properties and should be carefully tested to note the impact on cultured cells.
[52] Some researchers postulate that integrating removable polycaprolactone (PCL) fiber-based electrospun scaffolds under NaOH treatment enhances hydrophilicity as well as mitigating hydrophobicity, while promoting more efficient cell communication.
Most researchers take advantage of this to oxygenate both the PDMS and the circulating media, but this trait also makes the microfluidic system especially vulnerable to water vapor loss.
They postulated that future developments could transform this method into an assay that could test patient cancer cell response to known anti-cancer drugs.
Another group used a similar method, but instead of creating a 3D scaffolding, they employed several different PDMS coatings to determine the best option for studying cancer stem cells.
