FIELD OF THE INVENTION

The present invention provides a microfluidic channel and methods of removing bubbles from fluid in the microfluidic channel.

BACKGROUND OF THE INVENTION

Microfluidic channel have been extensively used in chemical analysis systems and BioMEMS applications for fluid transport. It is a technique for applications such as drug delivery, cell manipulation or chemical and biological sensing.

One of the main issues during manipulation and dosing of the small amounts of fluids in microfluidic channel is the formation of bubbles inside the fluid flow path at the reaction or mixing chamber within the microfluidic channel.

Generally, bubbles are very stable and are very hard to be naturally broken. The bubbles expand when they are in contact with each other to form bigger bubbles. This creates an air lock condition which causes clogging of the microfluidic channel when the size of the bubbles is almost equal to the microfluidic channel or at the fluid entry point or fluid exit point.

US20070167797 describes an ultrasound imaging system that transmits a broad beam of ultrasound into tissues that are perfused with blood containing microbubbles. The ultrasound has an intensity that is sufficient to destroy the microbubbles in the tissues. This prior art requires high external power.

US5831727 describes an apparatus that includes a plurality of chambers having an open top. Each chamber directs the moving liquid stream upwardly through an area of reduced diameter and then downwardly to an opening into an adjacent chamber. The bubbles are thereby urged upwardly to the top of the liquid where they burst and are vented to the atmosphere.

US5228889 describes a device comprising a channel of varying section for the liquid, the channel having a high point for collecting bubbles under gravity, and means for dynamically concentrating bubbles upstream from the high point, said means being constituted by a curved length of the channel situated upstream from the high point. In these two prior art documents, the bubbles are broken due to collision and they are collected and broken at the top of reservoir or fluid chamber only.

The invention discloses a microfluidic channel and methods to puncture and remove the bubbles along the fluid flow path without requiring external power. SUMMARY OF THE INVENTION

The advantage of this invention is that the disclosed apparatus and method are able to prevent clogging of the microfluidic channel by removing bubbles in the fluid flow path. A device for eliminating bubbles from fluid in a microfluidic channel is disclosed. Also disclosed are the methods for eliminating bubbles from fluid in microfluidic channel.

Accordingly, it is disclosed herein, a device for eliminating bubbles from fluid in a microfluidic channel, the device includes: a) a fluid entry point;

b) a base;

c) at least one primary sharp protuberance located substantially near to the fluid entry point wherein the primary sharp protuberance is provided on top of the base;

d) a fluid exit point; e) at least one secondary sharp protuberance located substantially near to the fluid exit point wherein the secondary sharp protuberance is provided on top of the base; and

f) a cover wherein the cover is located on top of the base; wherein when fluid which contains bubbles flow into the microfluidic channel, the at least one primary sharp protuberance and the at least one secondary sharp protuberance punctures the bubbles to enable the fluid exiting in the microfluidic channel to be substantially bubble free fluid.

It is also disclosed herein, a method for eliminating bubbles from fluid in microfluidic channel, the method including: a) flowing of fluid in a microfluidic channel through a fluid entry point;

b) puncturing of bubbles in the fluid by at least one primary sharp protuberance located substantially near to the fluid entry point in the microfluidic channel; c) puncturing of escaped bubbles by at least one secondary sharp protuberance located substantially near a fluid exit point in the microfluidic channel;

d) flowing of fluid through the fluid exit point.

Also disclosed herein, a device for eliminating bubbles from fluid in a microfluidic channel, the device includes: a) a fluid entry point;

b) a base;

c) at least one primary sharp protuberance located substantially near to the fluid entry point wherein the primary sharp protuberance is provided on top of the base;

d) a fluid exit point;

e) at least one secondary sharp protuberance located substantially near to the fluid exit point wherein the secondary sharp protuberance is provided on top of the base;

f) at least one air vent wherein the air vent is located in between the primary sharp protuberance and the secondary sharp protuberance; and g) a cover wherein the cover is located on top of the base; wherein when fluid which contains bubbles flow into the microfluidic channel, the at least one primary sharp protuberance punctures the bubbles and the at least one air vent removes the bubbles created after the larger bubbles have been punctured by the at least one primary sharp protuberance and the at least one secondary sharp protuberance punctures the escaped bubbles to enable the fluid exiting in the microfluidic channel to be substantially bubble free fluid. Yet, it is also disclosed herein a method for eliminating bubbles from fluid in a microfluidic channel, the method including: a) flowing of fluid in a microfluidic channel through a fluid entry point;

b) puncturing of bubbles in the fluid by at least one primary sharp protuberance located substantially near to the fluid entry point;

c) removing the smaller bubbles by one or more air vent; and

d) puncturing of escaped bubbles in the fluid by at least one secondary sharp protuberance located substantially near to the fluid exit point; BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 illustrates isometric view of microfluidic channel with enclosed sharp protuberances.

FIG 2 illustrates A-A cross-sectional view of microfluidic channel with enclosed sharp protuberances.

FIG 3 illustrates top view of microfluidic channel with enclosed sharp protuberances.

FIG 4 illustrated an embodiment of this invention.

FIG 5 illustrates an exemplary case using an embodiment of the invention.

FIG 6 (a) and (b) illustrates exemplary situations using an embodiment of the invention. FIG 7 (a), (b), (c) and (d) illustrates exemplary of sharp protuberance arrays. DETAILED DESCRIPTION OF THE INVENTION

The invention and its various embodiments is better understood by reading the description along with the accompanying drawings which appear herein for the purpose for illustration only and does not limit the invention in any way.

FIG 1 , 2 and 3 illustrates the view of the embodiment in different directions. FIG 1 illustrates the isometric view of microfluidic channel (104) with enclosed primary and secondary sharp protuberances (103), (106). FIG 2 illustrates the A-A cross-sectional view of microfluidic channel (104) and FIG 3 illustrates the top view of the microfluidic channel (104).

Fluid enters the microfluidic channel (104) through fluid entry (100). In microfluidic channel (104), bubbles will be formed due to the existence of air or gases inside the fluid in which equilibrium state is achieved between their outward air pressure and the inward surface tension of the fluid. The sharp protuberances (103), (106) edges break the molecular bond holding the structure of bubbles causing the bubbles to collapse and disintegrate.

The primary sharp protuberance (103) punctures the bigger bubbles into smaller ones. Air vent (102) removes the smaller bubbles created after the large bubbles are broken by primary sharp protuberance (103) so that it will not come in contact with other bubbles and expand into bigger bubble. The secondary sharp protuberance (106) punctures the escaped bubbles that were not removed by the air vent (102). After the bubbles are broken, the fluid exits through fluid exit (101 ).

FIG 4 illustrates the formation of microfluidic channel (104) with base (501 ) and a cover (502) wherein the cover (502) is located on top of the base (502). The primary sharp protuberance (103) and secondary sharp protuberance (106) are fabricated on the base (501 ) while the cover (502) is formed by silicon or glass substrates. The cover encapsulates the base (501 ) through bonding processes such as anodic, adhesives or fusion.

FIG 5 illustrates an exemplary implementation situation using the microfluidic channel (104) with enclosed sharp protuberance (103), (106) in a microfluidic mixing process. The invention resides within a microfluidic system which includes microfluidic mixer (601 ), microvalves (602), micropump (603), fluid reservoir (604) and outlet reservoir (606).

Sample and reagent fluid will flow from reservoir (604) and pass through micropump (603) into microfluidic channel (104) and microfluidic mixer (601 ) during pumping. The sample and reagent starts to mix in the microfluidic mixer (601 ) and generate byproducts in the form of gaseous bubbles. Generally, the bubbles formed will flow with the fluid through microfluidic channel (104). The bubbles will come in contact with primary sharp protuberance (103), and secondary sharp protuberance (106) inside the microfluidic channel (104) within the microfluidic mixer (601 ). The primary and secondary sharp protuberances (103), (106) will easily break the molecular bonding of the bubbles causing the bubbles to collapse and disintegrate into smaller bubbles. The fluid flows output is through outlet reservoir (606).

FIG 6 (a) and (b) illustrates exemplary situations of using the microfluidic channel to puncture bubbles. Fluid enters the microfluidic channel (104) through fluid entry (100). Figure 6 (a) illustrates puncturing of the bigger bubbles by primary sharp protuberance (103). Figure 6 (b) illustrates air vent (102) removing the smaller bubbles created after the large bubbles are broken by primary sharp protuberances (103). The secondary sharp protuberance (106) punctures the escaped bubbles that were not trapped by the air vent (102). After the bubbles are punctured, the fluid exits through fluid exit (101 ).

FIG 7 (a), (b), (c) and (d) illustrates different types of sharp protuberances arrays. Bubbles which are not broken by a single sharp protuberance (103), (106) might merge to form bigger bubbles and clog the fluid flow passage. Arrays of sharp protuberances is utilised to offer higher effectiveness of bubble puncturing process.