Bidirectional flow centrifugal microfluidic devices

Abstract

This invention relates to methods and apparatus for performing microanalytic and microsynthetic analyses and procedures. The invention particularly provides microsystem platforms for achieving efficient mixing of one or a plurality of fluids on the surface of the platform when fluid flow is motivated by centripetal force produce by rotation.

We claim:  
     
         1 . A centripetally-motivated microsystems platform comprising: 
 a) a rotatable platform comprising a substrate having an axis of rotation and a surface comprising one or a multiplicity of microfluidics structures embedded in the surface of the platform, wherein each microfluidics structure comprises 
 i) one or a plurality of fluid reservoirs,  
 ii) one or a plurality of detection chambers,  
 iii) one or a plurality of mixing microchannels  
 wherein the interior surface of each of the microchannels comprises a graded hydrophobic surface, wherein the hydrophobicity of the surface increases with distance from the axis of rotation, and wherein each of said fluid reservoir is fluidly connected to a mixing microchannel that is fluidly connected to a detection chamber, and wherein fluid within the microchannels of the platform is moved through said microchannels by centripetal force arising from rotational motion of the platform for a time and a rotational velocity sufficient to move the fluid through the microchannels.  
   
     
     
         2 . A centripetally-motivated microsystems platform comprising: 
 a) a rotatable platform comprising a substrate having an axis of rotation and a surface comprising one or a multiplicity of microfluidics structures embedded in the surface of the platform, wherein each microfluidics structure comprises 
 i) one or a plurality of fluid reservoirs,  
 ii) one or a plurality of detection chambers,  
 iii) one or a plurality of mixing microchannels  
 wherein the interior surface of each of the microchannels comprises a graded surface to volume ratio, wherein the surface to volume ratio increases with distance from the axis of rotation, and wherein each of said fluid reservoir is fluidly connected to a mixing microchannel that is fluidly connected to a detection chamber, and wherein fluid within the microchannels of the platform is moved through said microchannels by centripetal force arising from rotational motion of the platform for a time and a rotational velocity sufficient to move the fluid through the microchannels.  
   
     
     
         3 . A microsystems platform of  claim 1 , wherein the interior surface of each of the microchannels comprises a graded surface to volume ratio, wherein the surface to volume ratio increases with distance from the axis of rotation  
     
     
         4 . A method for mixing two or a plurality of different fluids, comprising the steps of: 
 a) applying a volume of a first fluid to one or a plurality of fluid reservoirs of a microsystem platform of  claim 1  when the platform is stationary;    b) applying a volume of a second fluid to one or a plurality of fluid reservoirs of a microsystem platform of  claim 1 , wherein the fluid reservoir containing the first fluid is the same fluid reservoir containing the second fluid, or the fluid reservoirs containing the first and second fluids are fluidly connected to the same mixing microchannel;    c) rotating the platform at an increasing rotational speed sufficient to motivate fluid flow from the fluid reservoir to the most distal extend of the mixing microchannel without motivating fluid flow into the detection chamber;    d) rotating the platform at a decreasing rotational speed until all fluid in the mixing microchannel returns to the fluid reservoir    e) repeating steps (c) and (d) for a number of repetitions sufficient to homogeneously mix the first and second fluids into a homogeneous mixture;    f) rotating the platform at a rotational speed greater than the maximum speed of rotation in step (c) at a speed sufficient to motivate the homogeneously mixed fluid into the detection chamber; and    g) detecting the homogenous mixture.    
     
     
         5 . A method for mixing two or a plurality of different fluids, comprising the steps of: 
 a) applying a volume of a first fluid to one or a plurality of fluid reservoirs of a microsystem platform of  claim 2  when the platform is stationary;    b) applying a volume of a second fluid to one or a plurality of fluid reservoirs of a microsystem platform of  claim 2 , wherein the fluid reservoir containing the first fluid is the same fluid reservoir containing the second fluid, or the fluid reservoirs containing the first and second fluids are fluidly connected to the same mixing microchannel;    c) rotating the platform at an increasing rotational speed sufficient to motivate fluid flow from the fluid reservoir to the most distal extend of the mixing microchannel without motivating fluid flow into the detection chamber;    d) rotating the platform at a decreasing rotational speed until all fluid in the mixing microchannel returns to the fluid reservoir    e) repeating steps (c) and (d) for a number of repetitions sufficient to homogeneously mix the first and second fluids into a homogeneous mixture;    f) rotating the platform at a rotational speed greater than the maximum speed of rotation in step (c) at a speed sufficient to motivate the homogeneously mixed fluid into the detection chamber; and    g) detecting the homogenous mixture.