WO2011122932A1

WO2011122932A1 - Planar micropump with integrated passive micromixers

Info

Publication number: WO2011122932A1
Application number: PCT/MY2010/000253
Authority: WO
Inventors: Hing Wah Lee; Bien Chia Sheng Daniel; Ismahadi Syono Mohd.; Ramdzan Buyong Muhd.
Original assignee: Mimos Berhad
Priority date: 2010-03-29
Filing date: 2010-11-08
Publication date: 2011-10-06
Also published as: MY169278A

Abstract

The present invention relates generally to a planar micropump with integrated passive micromixers (10) which enhances the mixing of two or more differing fluids thereby allowing an efficient and effective mixing action to be achieved thereby resulting in a more homogeneous mixture for a reliable chemical analysis.

Description

PLANAR MICROPUMP WITH INTEGRATED PASSIVE MICROMIXERS

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to a planar micropump with integrated passive micromixers which enhances the mixing of two or more differing fluids thereby allowing an efficient and effective mixing action to be achieved thereby resulting in a more homogeneous mixture for a reliable chemical analysis. BACKGROUND OF THE INVENTION

Rapid mixing is an essential step for most microfluidic systems used in biochemistry analysis, drug delivery, agriculture, environmental monitoring and sequencing or synthesis of nucleic acids. For many of these systems, micropump, microchannel and micromixers are the important elements required to ensure successful operations. Since miniaturization is the recent trend in analytical chemistry and life sciences, the development of micropump, microchannel and micromixers was intensified through utilization of MEMS-based fabrication technologies. In general, micromixers can be categorized as passive micromixers and active micromixers. Passive micromixers do not require external energy where the mixing process relies entirely on diffusion or chaotic advection while active micromixers use the disturbance generated by an external field for the mixing process.

There exist lots of micromixers fabricated through bulk- micromachining techniques that works as a stand-alone device and are integrated externally or as a discrete device. Thus, the current integration of micromixers in a microfluidic system is both challenging and expensive as it does not offer a complete mixing solution on the same wafer. Additionally, fabrications using conventional bulk- micromachining are both expensive and the system usually requires high power consumption. Until today, a planar micromixing system with integrated micropump has not been introduced.

Hence, the present invention will address the shortcoming of available inventions in a sense that a novel planar micropump with integrated passive micromixers fabricated using CMOS-compatible surface micromachining will be introduced. The simple constructions with the passive structures are robust, stable in operation and require minimal actuation voltage. The micromixers will be integrated within the micropump along with built-in microchannels as the fluid passage. The complete configuration will be fabricated in-plane on the same wafer for better economies of scale (cost reduction).

SUMMARY OF THE INVENTION

Accordingly, it is the primary aim of the present invention to provide a planar micropump with integrated passive micromixers wherein the whole device or system is integrated and fabricated in-plane on a single substrate (or the same wafer) thereby allowing total analysis, (sample preparation, pre-treatment, analytical reactions, detection, and results) to be combined in a single device or chip.

It is yet another object of the present invention to provide a planar micropump with integrated passive micromixers which saves energy as the passive micromixers which do not require external energy for actuation is capable of mixing two different fluids by diffusion without additional energy supply.

It is yet a further object of the present invention to provide a planar micropump with integrated passive micromixers which is capable of enhancing and inducing additional diffusion hence enabling a more efficient and effective mixing activity to be carried out resulting in a more homogeneous mixture for a reliable chemical analysis.

Yet another object of the present invention is to provide a planar micropump witli integrated passive micromixers wherein the use of a flow regulation device is not a necessity.

Yet a further object of the present invention is to provide a planar micropump with integrated passive micromixers which simplifies fabrication processes as only a single substrate is required hence capable of offering a complete mixing solution on the same susbtrate thereby capable of further miniaturisation for nanofluidic applications.

It is yet another object of the present invention to provide a planar micropump with integrated passive micromixers which facilitates portability of the overall system thereby allowing analysis to be performed close to the sample source.

Yet a further object of the present invention is to provide a planar micropump witli integrated passive micromixers which encourages or faciUtates rniniaturization to greatly reduce the volume of chemicals involved, typically to the microlitre and nanolitre ranges. Yet another object of the present invention is to provide a planar micropump with integrated passive micromixers having the ability to perform multiple different assays leading to reduced cost per assay.

It is a further object of the present invention to provide a planar micropump with integrated passive micromixers which although simple in construction is robust, stable in operation and requires minimal actuation voltage as low as below 5 volts (V).

Other and further objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in practice.

According to a preferred embodiment of the present invention there is provided,

A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis comprising at least a micropump; at least a fluid inlet port (4); at least a fluid inlet microchannel (6) to direct flow of fluids; at least a fluid outlet port (14); characterised in that said micropump is integrated with passive micromixers (10). In another aspect, the present invention provides,

A method of mixing at least two fluids comprising steps of, drawing at least two differing fluids from the fluid inlet port (4); directing the flow of said fluids via fluid inlet microchannel (6) to the micropump chamber (8) allowing the differing fluids to meet; activating the passive micromixers (10) situate in the micropump chamber (8) thereby mixing the fluids; exiting from the pump chamber (8) into the fluid exit microchannel (12); collecting mixed fluid in the fluid outlet port (14). BRIEF DESCRIPTION OF THE DRAWINGS

Other aspect of the present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a micropump structure of a fluid mixing apparatus for chemical analysis integrated with passive micromixers.

FIG. 2 is a cross sectional view of FIG. 1 at line A-A.

FIG. 3-A to D shows different types of currently known micromixers.

FIG. 4 is a schematic diagram conventional fluid mixing apparatus for chemical analysis.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practised without these specific details. In other instances, well known methods, procedures and/ or components have not been described in detail so as not to obscure the invention.

The invention will be more clearly understood from the following description of the embodiments thereof, given by way of example only with reference to the accompanying drawings, which are not drawn to scale.

Referring now to FIGS. 1 and 2, FIG. 1 is a micropump structure of a fluid mixing apparatus (2) for chemical analysis provided with integrated passive micromixers (10) and FIG. 2 is a cross sectional view of FIG. 1 at line A-A. The said fluid mixing apparatus (2) illustrated in FIG. 1 comprises at least a fluid inlet port (4), at least a fluid inlet microchannel (6) at least a micropump integrated with at least a micromixer (10) within a pump chamber (8), at least a fluid exit microchannel (12) and an fluid outlet port (14). The differing fluids to be mixed such as fluid samples and chemical reagents for chemical analysis procedure are stored in the fluid inlet port. In the preferred embodiment shown in FIG. 1 the fluid sample is stored in the first fluid inlet port (4A) and the reagent is stored in the second fluid inlet port (4B). The passage of fluid that is directed tlirough the said fluid inlet microchannel (6) to the pump chamber (8) where the micromixers (10) are located usually requires external means either manually (self-injection) or electronically- operated devices (micropumps). When the micropumps of the said fluid mixing apparatus (2) operates, fluid from the fluid inlet port (4) will be drawn into the fluid inlet microchannel (6) connected to the micropump chamber (8). The. fluid sample from the first fluid inlet port ( A), is drawn into a first fluid inlet microchannel (6A) and the reagent from the second fluid inlet port (4B) is drawn into a second fluid inlet microchannel (613); the first and second fluid inlet microchannel (6A) (6B) are generally and collectively referred to as the fluid inlet microchannel indicated by reference numeral (6). Once fluid exits the said fluid inlet microchannel (6) and reaches the micropump chamber (8), both the reagents and sample solutions will meet. However, since the fluid flow is typically slow moving and laminar in nature, the fluid will not be able to mix effectively if left alone (as in conventional models described below and illustrated in FIG. 4). This is where the micromixers (10) come into great assistance. Both the reagents and the sample will pass through the micromixers (10) [which can be of any general constructions, some of which are illustrated in FIGS. 3-A to 3-D] integrated in the micropump and assisted mixing will occur. The diaphragm of the micropump can typically be driven by electrostatic, thermo-pneumatic or bimetallic actuation. Since the micropump is already actuated at this stage, the pumping action or hydrostatic potential created by the micropump will enhance mixing of the fluid with additionally induced diffusion and the fluid flow will be restructured in a way which results in a faster rate of mixing and in a more efficient manner.

The mixed fluid then exits from the pump chamber (8) into the fluid exit microchannel (12) where it is then directed to the fluid outlet port (14) for collection.

In contrast in conventional mixing systems as illustrated in FIG. 4, when the micropumps of the conventional fluid mixing apparatus (20) operates, fluid from the conventional fluid inlet port (22) will be drawn into the fluid microchannels (24) connected to the micropump chamber

(26). The fluid upon emerging from the micropump chamber (26) continues to travel separately in fluid microchannel (24) and meet in the micromixer chamber (28). Microvalves (30) are provided to control the flow of fluids. However, since the fluid flow is typically slow moving and laminar in nature, the fluid will not be able to mix effectively. The present invention which has passive micromixer (10) integrated in the micropump as described above and illustrated in FIG. 1 and 2 enhances the mixing of two or more differing fluids as the pumping effect or hydrostatic potential created by the activated micropump induces additional diffusion to occur to achieve a more homogeneous fluid mixture. Although only two fluid inlet ports (4) and only two fluid inlet microchannels (6) have been described and illustrated it is to be understood that the number of fluid inlet ports or inlet microchannels may be more than two, as what is advantageous is the efficient and effective mixing of at least two fluids.

Chemical analysis procedure that requires flow mixing of liquid samples and chemical reagents can be achieved using micromixers fabricated through MEMS-based fabrication technology. In this invention passive micromixers (10) are selected as they do not require external energy for mixing of different fluids as mixing is achieved through diffusion or chaotic advection. The efficiency and success of the mixing of fluids also depends upon the micromixer constructions and surface conditions. Referring to FIGS. 3-A to D there is shown different known types of micromixers in several configurations which may be applicable in this invention. Fig. 3-A shows a parallel-plate or channel type of micromixers wherein the fluid sample (5A) and chemical reagent (5B) will be segmented into smaller fluid flow upon contact with the parallel- plate or channel as indicated by the complete-line arrow (A) and dash- line arrow (B) respectively to create disturbance to the flow and allowing mixing. FIG. 3-B illustrates a Y-mixer type of micromixer disclosed by inventor Hessel et. Al wherein the fluid sample (5A) and chemical reagent (513) from separate channels will converge at the intersection to allow both fluid to come into contact and mix. FIG. 3-C illustrates three planar type of micromixer namely obstacles on wall [FIG. 3C(a)], obstacles in channel [FIG. 3C(b)] and zig-zag [FIG. 3C(c)] wherein the shape of the obstacles will cause, the fluid flow to change direction and enable both fluid sample (5A) and chemical reagent (5B) to come in contact to promote mixing. FIG. 3-D illustrates spiral or circular or serpentine type of micromixers as disclosed in US7160025 wherein the circular pressure or momentum created from the fluid sample (5A) and chemical reagent (513) flow creates higher collision between the fluid sample (5A) and chemical reagent (5B) hence increases the mixing effects.

The present invention generally does not need a flow regulation device (microvalve) where microchannels as fluid passage will be sufficient to direct fluids (reagents or buffer or sample) to and from the micropump with integrated passive micromixers (10). If fluid flow regulation is required, the present invention may also include an integrated valve at the entry or exit fluid microchannel (6) of the micropump. When driven electrostatically, the said micropump is possible to be operated at a low voltage of less than 5V. The overall invention is designed to ease fabrication complexities where only a single substrate is required and is capable of further miniaturisation for nanofluidic applications. The planar design wherein the said micropump with integrated passive micromixers (10) are fabricated utilizes CMOS-compatible surface micromachining fabrication process flow which presents the possibility of mass production, integration with other electronics and cost reductions. The complete integrated form of such systems is more commonly known as laboratory- on-a-chip (LOC) or a micro-total-analysis-system (μΤΑ5) wherein the whole device or system is integrated and fabricated in-plane on a single substrate (or the same wafer) thereby allowing total analysis (sample preparation, pre-treatment, analytical reactions, detection, and results) to be combined in a single device or chip.

While the preferred embodiment of the present invention and its advantages has been disclosed in the above Detailed Description, the invention is not limited thereto but only by the spirit and scope of the appended claim.

Claims

WHAT IS CLAIMED IS:

1. A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis comprising, at least a micropump; at least a fluid inlet port (4); at least a fluid microchannel (6) to direct flow of fluids; at least a fluid outlet port (14); characterised in that said micropump is integrated with passive micromixers (10).

2. A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis as in Claim 1 further characterised in that all devices or system are fabricated in-plane on a single substrate.

3. A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis as in Claim 1 or 2 wherein the said micropump with integrated passive micromixers (10) are fabricated using CMOS-compatible surface micromachining.

4. A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis as in Claim 1, 2 or 3 wherein additional mixing action is provided indirectly by the pumping action of the micropump or the hydrostatic potential created by the activated micropump.

5. A fluid mixing apparatus (2) capable of mixing at least two different fluids for chemical analysis in Claim 1, 2, 3 or 4 wherein enhanced mixing of the said fluids is by additionally induced diffusion or restructured flow of fluids.

6. A method of mixing at least two fluids for chemical analysis comprising steps of, drawing at least two differing fluids from the inlet port (4); directing the flow of said fluids via fluid inlet microchannel (6) to the micropump chamber (8) allowing the differing fluids to meet; activating the passive micromixers (10) situate in the micropump chamber (8) thereby mixing the fluids; exiting from the pump chamber (8) into the fluid exit microchannel (12); collecting mixed fluid in the fluid outlet port (14).