Fluidic devices

Details Fluidic devices Fluidic devices

1998-03-12

2001-11-20

Yuen, Henry C. (Department: 3747)

Pumps

One fluid pumped by contact or entrainment with another

Liquid piston

C417S050000

Reexamination Certificate

active

06318970

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to fluidic devices, and particularly microfluidic devices.
BACKGROUND OF THE INVENTION
Microfluidic devices are becoming increasingly critical to biochemical analysis. These devices may have channels whose cross-sections are in the order of 1 &mgr;m to 1000 &mgr;m A fluid containing a sample to be analyzed and a reagent for activating the sample are delivered along channels to a reaction zone in the microchip. Pumping of the fluid is often carried out with external pumps, or electrical pumps that rely upon principles such as electroosmosis, electrophoresis and dielectrophoresis. When external pumps are used, problems can arise in both sample and reagent delivery.
For example, in sample delivery, transfer of sample to the chip may result in pressure differentials in excess of the pumping capacity, with resulting pressure fluctuations. In reagent delivery, the channels in the chip must be manually primed with reagent, with risk of cross-contamination.
SUMMARY OF THE INVENTION
There is thus a need for an on chip pump for use with microchips.
The invention provides a device that provides isolation and sample delivery in a microchip while not introducing large dead volumes. In addition, the use of the micropump in the channel allows pre-priming of the microchip, thus reducing the time in which the microchip is exposed to contaminants.
According to a first aspect of the invention, a pump pumps fluid along a channel by moving a drive fluid in the channel under the influence of a force field that is generated externally to the channel. The drive fluid is preferably a ferrofluid, and the force field is preferably a variable magnetic field. Drive fluid, driven by variation of the magnetic field, drives driven fluid through the channel. The drive fluid is recirculated, in one case by rotating the drive fluid within an enlargement in the channel, and in another case by returning the drive fluid along a return channel. The channel is preferably a microchannel in a microchip. The channel and pump may be formed between two plates forming a microchip. The channel may be as small as 1 &mgr;m to 100 &mgr;m in its cross-sectional dimensions. A valve is formed by using a ferrofluid plug as a movable barrier for fluids in a channel. Methods of pumping fluids by using an in channel drive fluid and exterior drive are also disclosed.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.


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