Droplet Dispensing

Digital microfluidic architecture is under software-driven electronic control, eliminating the need for mechanical tubes, pumps, and valves that are required for continuous-flow systems. The compatibility of each chemical substance with the electro-wetting platform must be determined initially. Compatibility issues include the following (1) Does the liquid s viscosity and surface tension allow for droplet dispensing and transport by electrowetting ... 

H. Ren, R. B. Fair, and M. G. Pollack, Automated on-chip droplet dispensing with volume control by electro-wetting actuation and capacitance metering, Sensors and Actuators B-Chemical, vol. 98, no. 2-3, pp. 319-327, Mar. 2004. 

XM. Waldvogel, D. Poulikakos, D.B. Wallace, and R.M. Marusak, Transport phe-nonmena in picoliter size solder droplet dispensing on a composite substrate. Journal of Heat Transfer 118 (1996) 148-156. 

The most well known and successful application of microfluidics is inkjet printing. Sample volumes in the nanoliter-picoliter range are very difficult to handle by conventional pipetting and in this context, droplet dispensers for sample handling are finding increased use in life science and chemistry. Therefore special tools need to be developed (Figure 49.3). 

BoiUng and Evaporation in Microchannels Bubble-Actuated Microfluidic Switch Cavitation in Microdomains Droplet Dispensing > Flow Boiling Instability... 

Droplet-based Lab-on-a-Chip devices represent a class of microfluidic systems that have been developed to miniaturize chemical, biochemical, or cellular analysis. These devices utilize various droplet dispensing and manipulatiOTi mechanisms to isolate and control liquid-phase droplets of samples and/or reagents surrounded by a gas or an immiscible liquid. The droplets may be completely surrounded by the medium or may be placed onto a solid surface whose material properties are chosen to provide droplet confinement, chemical functionalization, or control of droplet motion. The devices also have some type of assay readout method with associated hardware, software, and data display. 

Various examples of the use of droplet dispensing within the life sciences [1] are droplet-based Lab-on-a-Chip systems, fabrication of microarrays, combinatorial chemistry and high-throughput screening in drug discovery, inhalers in medical therapeutics, and many more. 

Droplet Dispensing, Fig. 3 Dispensing Well Plate offering 384 dispensing units in parallel made by silicon bulk micromachining (pitch of 4.5 mm)... 

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