High Speed Droplet-based Delivery System for Passive Pumping in Microfluidic Devices
Summary
A novel microfluidic system has been developed using the phenomenon of passive pumping and a user controlled fluid delivery system. This microfluidic system has the potential to be used in a wide variety of biological applications given its low cost, ease of use, volumetric precision, high speed, repeatability and automation.
Abstract
A novel microfluidic system has been developed that uses the phenomenon of passive pumping along with a user controlled droplet based fluid delivery system. Passive pumping is the phenomenon by which surface tension induced pressure differences drive fluid movement in closed channels. The automated fluid delivery system consists of a set of voltage controlled valves with micro-nozzles connected to a fluid reservoir and a control system. These voltage controlled valves offer a volumetrically precise way to deliver fluid droplets to the inlet of a microfluidic device in a high frequency manner. Based on the dimensions demonstrated in the current study example, the system is capable of flowing 4 milliliters per minute (through a 2.2mm by 260um cross-sectional channel). Based on these same channel dimensions, fluid exchange of a point inside the channel can be achieved in as little as eight milliseconds. It is observed that there is interplay between momentum of the system (imparted by a combination of the droplets created by the valves and the fluid velocity in the channel), and the surface tension of the liquid. Where momentum provides velocity to the fluid flow (or vice-versa), equilibration of surface tension at the inlet provides a sudden stop to any flow. This sudden stop allows the user to control the flow characteristics of the channel and opens the door for a variety of biological applications, ranging anywhere from reagent delivery to drug-cell studies. It is also observed that when nozzles are aimed at the inlet at shallow angles, the droplet momentum can cause additional interesting fluid phenomena, such as mixing of multiple droplets in the inlet.
Protocol
In this report we demonstrate a fluid delivery method that uses small droplet surface tension to pump a desired volume through a microfluidic channel in order to achieve a number of different fluid phenomena. For example, the user may wish to flow a single fluid as fast as possible, or deliver multiple fluids in rapid succession to create specific fluidic patterns. In order to do this, the user must first have an application built around a microfluidic device. The microflluidic device does not need to be bonded, but sho…
Discussion
- For high speed passive pumping, if the right combination of frequency and per pulse volume (due to the correct open time) is chosen, user should see what seems to be a static drop or shell at inlet and a very fast flow rate inside channel. If overflow occurs, the open time and/or the frequency are too high.
- To detect momentum/surface tension interactions, the user should pump one pulse at a time and observe the intra-channel environment while pulse is occurring (from beginning to end). It is recommended by the authors to use…
Acknowledgements
Funding was provided by the Wisconsin Institute of Discovery.
Materials
| Material Name | Type | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Sylgard 184 Silicone elastometer base | Dow Corning | MSDS No.: 01064291 | ||
| Sylgard 184 Silicone elastometer curing agent | Dow Corning | MSDS No.: 01064291 | ||
| VHS Microdispensing Starting kit | The Lee Company | IKTX0322000A | ||
| Miniature Holders | Bioscience Tools | MH-2 | ||
| LabVIEW | National Instruments | Control System | ||
| 1.14mm I.D. tubing | Scientific Commodities Inc. | BB31695-PE/7 | ||
| 1.57mm I.D. tubing | Scientific Commodities Inc. | BB31695-PE/10 | ||
| 20 mL BD™ Luer-Lok Tip Syringe, non-sterile | BD | 301032 |
References
- Berthier, E., Beebe, D. J. Flow rate analysis of a tension driven passive micropump. Lab Chip. 7, 1475-1478 (2007).
- Duffy, D. C., McDonald, J. C., Schueller, O. J. A., Whitesides, G. M. Rapid Prototyping of Microfluidic Systems in Poly(dimethylsiloxane). Anal. Chem. 70, 4974-4984 (1998).
- Harris, J., Lee, H., Vahidi, B., Tu, C., Cribbs, D., Cotman, C., NL, J. e. o. n. Non-plasma Bonding of PDMS for Inexpensive Fabrication of Microfluidic Devices. J Vis Exp. (9), (2007).
- Walker, G. M., Beebe, D. J. A passive pumping method for microfluidic devices. Lab Chip. 2 (3), 131-134 (2002).
Tags
High-speedDroplet-based Delivery SystemPassive PumpingMicrofluidic DevicesFluid MovementVoltage-controlled ValvesMicro-nozzlesFluid ReservoirControl SystemVolumetrically PreciseHigh FrequencyFlow RateChannel DimensionsFluid ExchangeInterplay Between Momentum And Surface TensionFlow CharacteristicsBiological Applications
Cite This Article
Resto, P. J., Mogen, B., Wu, F., Berthier, E., Beebe, D., Williams, J. High Speed Droplet-based Delivery System for Passive Pumping in Microfluidic Devices. J. Vis. Exp. (31), e1329, doi:10.3791/1329 (2009).