Motorized actuation system to perform droplet operations on printed plastic sheets

Abstract

We developed an open microfluidic system to dispense and manipulate discrete droplets on planar plastic sheets. Here, a superhydrophobic material is spray-coated on commercially-available plastic sheets followed by the printing of hydrophilic symbols using an inkjet printer. The patterned plastic sheets are taped to a two-axis tilting platform, powered by stepper motors, that provides mechanical agitation for droplet transport. We demonstrate the following droplet operations: transport of droplets of different sizes, parallel transport of multiple droplets, merging and mixing of multiple droplets, dispensing of smaller droplets from a large droplet or a fluid reservoir, and one-directional transport of droplets. As a proof-of-concept, a colorimetric assay is implemented to measure the glucose concentration in sheep serum. Compared to silicon-based digital microfluidic devices, we believe that the presented system is appealing for various biological experiments because of the ease of altering design layouts of hydrophilic symbols, relatively faster turnaround time in printing plastic sheets, larger area to accommodate more tests, and lower operational costs by using off-the-shelf products.

Bioinspired Unidirectional Liquid Spreading Channel–Principle, Design, and Manufacture

“…technologies. [1][2][3][4][5][6][7][8][9][10] Although several strategies, including chemical modification, hetero-wettability fabrication, and temperature differences, have been proposed to induce directional liquid motion, the liquid motion is usually limited to the gradient on the surface and easily influenced by the extra energy including vibrations and heat. [11][12][13][14][15][16][17] In recent years, the discovery of numerous natural systems that enable directional liquid transport due to their unique surface structure at the micro-and nanoscale (such as cactus, the pitcher plant, and lizard and spider silk) offers a biomimetic way in the development of an efficient directional spreading surfaces.…”

“…Mater. Interfaces 2020, 7,1901791 www.advmatinterfaces.de wettability on the solid surface. 2) The switch structure exists in each directional structure.…”

“…Mater. Interfaces 2020, 7,1901791 In this case, liquid can still be pinned when it flows over the switch structure in negative direction. Thus, it can be seen that the biological structure has greater advantages.…”

“…Mater. Interfaces 2020, 7,1901791 principles of unidirectional channels were summarized. The application of machining cutting in bionic structure manufacturing and the principle of the unidirectional structure design will open up new avenues for the practical application of bionic structure in engineering field.…”

Prediction of Droplet Production Speed by Measuring the Droplet Spacing Fluctuations in a Flow-Focusing Microdroplet Generator

“…More importantly, droplet production speed is mostly obtained by online detection, while monodisperse droplets are generated in a flow-focusing microdroplet generator [22,23]. While some new methods of droplet formation have been provided for monodisperse droplet production [24][25][26], to the best of our knowledge, the nonlinear relationship between droplet production speed and fluid flow rate is mainly qualitatively discussed in experiments of droplet generation in the flow-focusing microchannel [27].…”