Patent Application: US-9808708-A

Abstract:
microscale or nanoscale apparatus for stopped - flow , quenched flow or continuous flow reaction apparatus where fluids or gases are mixed in a device composed of parallel or serial assembly of the basic fluid - containing cell having a longitudinal axis , a cross - sectional area generally perpendicular to the longitudinal axis , and at least one connected crossing cell having a longitudinal axis , a cross - sectional area generally perpendicular to said longitudinal axis and a fluid motivating force interacting transversally with the fluids flow .

Description:
in the following description of the preferred embodiment , reference is made to the accompanying drawings which form a part hereof , and in which is shown by way of illustration a specific embodiment in which the invention may be practiced . it is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention . the mechanism of the rapid laminar mixing of fluids induced by transversal jet flows is described numerically and experimentally herein . by means of a simplified model , namely , a microfluidic device comprised of a main channel ( mixing cell ) and transversal channels , it is shown that jet flows induce the formation of a recirculation region providing a dynamical mechanism to produce rapid and efficient mixing . the numerically predicted dynamical phenomenon is demonstrated experimentally . an exemplary application of this invention would be to mix a protein ( e . g . cytochrome c ) and a basic or acid buffer , to analyze its folding or unfolding structure and kinetic behavior . current methods require turbulent mixing and are generally high compound consuming . another use might be to analyze the polymerization of molecules like ethene or propene . another use might be to study the rna folding . the present invention comprises a device that can produce mixing under laminar conditions for applications in stopped flow , continuous flow and quenched flow analysis . the present invention also comprises a method that can produce mixing under laminar conditions where the manipulation of the fluids to achieve mixing is done by the action of the jet flow coming from one or more transverse cells . the present invention also comprises a process that can produce mixing under laminar conditions where a least one solution resulting from the mixing of reagents has been created . this disclosure first introduces an apparatus and a procedure where two fluids are introduced , then mixed , in a micromixer device . the micromixing produced by a microfluidic device comprises of a main fluid containing cell ( main channel ) and a pair of transverse channels . jet flows resulting from the oscillations in the transverse channels perturb the main stream to create vortices and generate an efficient mixing . the design of the mixer is composed of a main channel where the fluids are injected , and one or more transversal channels to manipulate the fluids and increase the mixing [ 31 , 32 , 36 , 37 ]. an example of the basic cell mixing device 100 design is shown fig1 ( a ) and fig1 ( b ). fig1 ( a ) is a top view of the 16 mm by 16 mm mixing device 100 microfabricated using conventional techniques . the device 100 was deep reactive ion etched in silicon , and anodically bonded to a cover glass . the mixing device 100 consists of a main channel 102 where the two fluids 104 , 106 to be mixed are injected at inlet a 108 and inlet b 110 . the two fluid streams 112 , 114 move from left to right in the main channel 102 . three pairs of secondary channels ( 116 a , 116 b ), ( 118 a , 118 b ) and ( 120 a , 120 b ) are positioned perpendicular to the main channel 102 . the fluid motion in these secondary channels ( 116 a , 116 b ), ( 118 a , 118 b ) and ( 120 a , 120 b ) is driven at specified amplitudes and frequencies , and perturbs the flow field in the main channel 102 to enhance mixing . in the present study only the central pair of secondary channels ( 118 a , 118 b ) is activated . the main channel 102 is 2h wide and l = 13 . 5h long . the secondary side channels 116 ( a , b ), 118 ( a , b ) and 120 ( a , b ) are h / 2 wide , 5h long and separated from each other by a distance of 3h . the depth of the channels 102 , ( 116 a , 116 b ), ( 118 a , 118 b ) and ( 120 a , 120 b ) is h where h = 100 μm . the flow in the secondary channels 118 ( a , b ) is driven by high - frequency oscillating syringe pumps 122 ( fig1 ( b )) and a syringe pump 124 injects the two fluids 104 , 106 to be mixed into the device 100 ( fig1 ( b )). two fluids 104 , 106 are injected in the device 100 through inlet a 108 and b 110 ( fig1 ) at steady and constant flow rate . the flow 112 , 114 is fully developed when reaching the intersection 124 of the side channels 118 ( a , b ) [ 31 ]. the fluids 104 , 106 are then manipulated by the transverse oscillating jet flow . the velocity condition v sc = v 0 sin ( ωt ) is imposed at the entrance 126 of the side channels 118 ( a , b ). the reynolds number associated with the secondary channel flow is defined as and b = 50 μm is the secondary channel width . the present invention makes the various flow parameters non - dimensional , thereby obtaining a non - dimensional amplitude â = a / a , frequency where a = 2h is the chamber 102 width and b = h / 2 the side channel 118 a , b width . the unsteadiness in the flow in the secondary channels is described by the strouhal number , the main flow consists of two unmixed , miscible fluids 104 , 106 entering the chamber 102 . the working fluids are degassed and deionized water . in order to distinguish the two fluid streams 112 , 114 , one stream was seeded with 98 nm dia . fluorescent polystyrene particles , with a diffusion coefficient of d ps = 2 . 2 μm 2 / s . as they enter the mixing chamber , the interface is clear and only a slight amount of mixing occurs due to molecular diffusion ( diffusion length is calculated to be 0 . 7 μm ). when the side channels 118 ( a , b ) are activated for re sc above the threshold of 11 , the two fluid streams ( or flows ) 112 , 114 ( which are not mixed just before the intersection 124 ) are manipulated by the transverse flow from the side channels 118 ( a , b ) and become fully mixed downstream of the intersection 124 . also shown is the outlet 128 of the device 100 . a similar analysis applies to activation of additional side channels 116 ( a , b ) and 120 ( a , b ). fig2 is a picture of a basic cell comprising the mixing channel 200 crossing by two pairs of side ( secondary ) channels ( 202 a , 202 b ) and ( 204 a , 204 b ), wherein the second pair ( 204 a , 204 b ) is activated , fluids are flowing from left to right , amplitude and frequency are optimized , the reynolds number is re = 2 . 6 and the flow rate is fixed at 277 pl / s ( picoliters per second ). fig2 is an instantaneous snapshot ( top view ) of the mixing performance for optimized frequency and amplitude . as the fluids approach the intersection 206 from the left , two well discernible bands 208 , 210 of fluid are visible , and within about 100 microns downstream of the intersection 206 the fluids are thoroughly mixed . the degree of mixing can be quantified by the so - called mixing variance coefficient function φ ( mvc ) [ 31 - 33 ]. complete mixing is achieved when φ = 0 and no mixing corresponds to φ = 0 . 25 . the optimum amplitude and frequency of the secondary channel oscillations were determined systematically by measuring the mvc as a function of non - dimensional frequency 0 & lt ;{ circumflex over ( f )}& lt ; 2 . 5 and amplitude 1 & lt ; â & lt ; 3 . fig3 ( a ) shows the mvc as a function of { circumflex over ( f )} and â . in region c , where high frequencies and amplitudes are achieved , the mixing is excellent ( mvc ˜ 0 . 01 ). fig3 ( b ) is a block of three pictures 1 , 2 and 3 , showing the flow ( mvc ) at the same location in the main channel 300 after mixing corresponding to the three sets of parameters ( amplitude , frequency ) of oscillation 1 , 2 and 3 marked in fig3 ( a ). in order to improve the present invention &# 39 ; s understanding of the mixing mechanism , the present invention examines the fluid motion and scalar fields at the intersection of the secondary channel and the main channel . the secondary channels 204 a , 204 b are perpendicular to the main channel 200 and have sharp corners 212 . this creates a sudden expansion for flow being injected into the main channel 200 from the secondary channels 204 a and 204 b as shown in fig2 . for sufficiently large reynolds numbers , re sc & gt ; 11 , nonlinear effects are prominent at the intersection 206 and two recirculation vortices 400 appear ( see fig2 and 4 ). fig4 ( a ) is an instantaneous snapshot of the velocity field at the intersection of the mixing channel 402 and the side channel 404 , after a quarter of a period of oscillation , obtained by micro particle image velocimetry [ 34 ] ( μpiv ), and fig4 ( b ) is a direct numerical simulation of the flow for the same configuration and conditions using fluent ™ ( lebanon , n h ) ( see bottausci et al . [ 31 ] for details ). the vortices develop and grow as the flow velocity reaches its maximum velocity in the side channel ( data not shown ). as the jet flow slows down , the recirculation does not stay symmetrical , because of the influence of the velocity in the main channel , u . the vortices vanish just after the velocity in the secondary channels reaches zero . 2 ) the taylor - aris dispersion taking place mainly in the side channels 500 , fig5 ( a ), but also in the main channel 502 ( fig5 ( b )). fig5 ( a ) is a picture of the flow in one of the transverse channels 500 , after few oscillations , where fluids are mixed by taylor - aris dispersion , and fig5 ( b ) is a picture of the flow in the main channel 502 where mixed fluids are injected from the side channel 500 . the layers entering the side channel are stretched , due to the contraction of the secondary channel . inside the secondary channels , there is significant taylor - aris dispersion due to high shear rates , which further enhances the mixing process . every half cycle , mixed fluid coming from the side channel is injected in the main channel . depending on the applications , a valve can be added at the end of the main channel to rapidly stop the flow . the valve can be , for example , a mechanical valve ( piezohydraulic , pneumatic and thermopneumatic or pressure driven ), or a multiphase valve ( bubble valve or two phase flow where the flow is suddenly stopped by freezing a section of the main channel ). fig6 illustrates a mixing apparatus 600 ( micromixer device ) for mixing two or more fluids ( 602 , 604 ), comprising a fluid containing cell 606 ( or main channel ), injection channels 608 , 610 for injecting two or more main fluid flows 602 a , 604 a ( of fluids 602 and 604 , respectively ) into the fluid containing cell 606 , a pair of side cells 612 , 614 for introducing a secondary fluid flow 616 into the fluid containing cell 606 at an intersection 618 between the side cells 612 , 614 and the fluid containing cell 606 , and a valve 620 at the end of the main channel 606 enabling flow to be stopped . upstream of the intersection 618 , fluids 602 and 604 are unmixed . the secondary fluid flow 616 , which oscillates , perturbs the main fluid flows 602 a , 604 a in the fluid containing cell 606 ( to create structures in the flows 602 a , 604 a , leading to a mixing of the flows 602 a , 604 a ) so that downstream of the intersection 618 , the fluids flows 602 a , 604 a are fully mixed . the mixing process and apparatus described here constitute an efficient and rapid micromixer that can be viewed as a module to be incorporated in already existing or to - be - developed apparatuses . this work opens the door to more sophisticated hydrodynamic behavior and apparatus design for micromixing applied to stopped flow , quenched flow or continuous flow apparatuses . specifically , the basic unit described above can be operated in parallel to provide for multiple reactions where a specified cascade of reactions is to occur , such as in experimental studies of gene regulatory networks . examples of such operation are provided in fig7 and 8 . fig7 is a schematic of a micromixer configuration 700 comprising three mixing apparatuses a , b and c , wherein micromixer a has two injection channels 702 , 704 and a pair of transverse channels 706 , 708 for oscillations , micromixer b has injection channels 710 , 712 and a pair of transverse channels 714 , 716 , micromixer c has transverse channels 718 , 720 , a product is formed in parallel using the micromixers a and b mounted in parallel and then these products ( from a and b ) can be mixed together using the micromixer c mounted in series with micromixers a and b , and the valve 722 enables the flow to be stopped . fig8 is a schematic of a micromixer configuration 800 comprising two mixing apparatuses a and b mounted in series , wherein micromixer a has injection channels 802 , 804 and transverse channels 806 , 808 , wherein a product is formed using the micromixer a , then this product can be mixed together with another reactant ( introduced in injection channel 810 ) using the micromixer b mounted in series with micromixer a , and the valve 812 at the end of micromixer b enables the flow to be stopped . micromixer b has transverse channels 814 and 816 for oscillations . in addition , simultaneous reactions of multiple species can be pursued using the invention embodiment shown in fig9 . fig9 is a schematic of a mixing apparatus 900 comprising five injection channels 902 , 904 , 906 , 908 , 910 , a main channel 912 and a pair of transverse channels 914 and 916 for oscillations , wherein a product is formed by mixing simultaneously the five reactants inputted through the injection channels 902 - 910 and the valve 918 at the end of the main channel 912 enables the flow to be stopped . this invention thus introduces a method of mixing and a device , that can produce mixing under laminar conditions for applications in stopped flow , continuous flow and quenched flow analysis . additionally , designs utilizing the basic cell to operate in parallel with other such cells can be used to perform c - dna experimentation and elisa testing , as well as kinase - based assays . the fluid containing cell and side cells may be channels having a longitudinal axis and a cross - sectional area , wherein the fluid flows generally along the longitudinal axis . the fluid - containing cell cross - sectional area may be symmetrical or non - symmetrical . the cross - sectional area of the main fluid - containing cell and the side cells may be identical or different . the angle between the main fluid - containing cell and the side cell may be 90 degrees or any other angle . one or more walls of the mixing apparatus may be smooth or have asperities . the fluid containing cell and side cell may have microscale dimensions or less . at least one pair of transverse side cells is necessary . the secondary fluid flow may perturb flow in the main fluid containing cell in a variety of ways . for example , the secondary fluid flow may create recurrent circulating fluid flow within the fluid containing cell or cause laminar flow conditions in the fluid containing cell . the secondary fluid flow may be oscillatory , for example , vary in time or intensity , which oscillation may be applied by an external mechanism or an internal mechanism . the secondary fluid flow may introduce a fluid motivating shear into the transverse cell and or into the main cell . fluids may be reagents introduced individually , sequentially , or by pair in the main fluid containing cell . the introduction of reagents may be delayed in time . the introduction of at least one reagent may be downstream from the previous reagent introduction . there are no limitations on the nature of the fluids that may be contained in the fluid containing cell . for example , the fluid may be a liquid or a gas . the fluid in the transverse cell may be identical , different or a mixture of one of the fluids in the main cell . two or more fluids may be injected in the main fluid containing cell before the intersection with the side / intersecting cell . the present invention may also comprise a system of one or more mixing apparatuses mounted in series or in parallel , so that one or more mixing processes may be performed in series or in parallel . consequently , the present invention discloses a method of a method of manipulating two or more fluids , comprising perturbing two or more fluid flows with one or more oscillating side flows , wherein the oscillating side flow causes the two or more fluid flows to homogeneously mix under laminar conditions and within 100 milliseconds . 1 . dobson c . m . protein folding and misfolding nature 426 : 884 2003 . 2 . dearmond , s . j ., and prusiner , s . b . 1997 . molecular neuropathology of prion diseases . in the molecular and genetic basis of neurological disease . r . n . rosenberg , s . b . prusiner , s . dimauro , and r . l . barchi , editors . butterworth - 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