Microfluidic element for thoroughly mixing a liquid with a reagent

Abstract

A microfluidic element for thoroughly mixing a liquid with a reagent used for the analysis of the liquid for an analyte contained therein and a method thereof are disclosed. The microfluidic element has a substrate and a channel structure. The channel structure includes an elongate mixing channel and an output channel. The mixing channel has an inlet opening and an outlet opening, and is implemented to mix the reagent contained therein with the liquid flowing through the inlet opening into the mixing channel. The outlet opening of the mixing channel is in fluid communication to the output channel. The outlet opening is positioned closer to the middle of the length of the mixing channel than the inlet opening.

1 . A microfluidic element for thoroughly mixing a liquid with a reagent used for analyzing the liquid for an analyte contained therein, the microfluidic element comprising:
 a cover layer;   a substrate; and   a channel structure enclosed by the substrate and the cover layer, wherein the channel structure includes an elongate mixing channel and an output channel, wherein the mixing channel has an inlet opening and an outlet opening, and the mixing channel is adapted for mixing the reagent contained therein with the liquid flowing through the inlet opening into the mixing channel, and wherein the outlet opening of the mixing channel is in fluid communication with the output channel, and the outlet opening is located closer to the middle of the length of the mixing channel than the inlet opening.   
     
     
         2 . The microfluidic element according to  claim 1 , wherein the microfluidic element is a test carrier. 
     
     
         3 . The microfluidic element according to  claim 1 , wherein the channel structure is a sample analysis channel which includes a sample inlet opening and a measuring zone. 
     
     
         4 . The microfluidic element according to  claim 1 , wherein the microfluidic element is rotatable about an axis of rotation. 
     
     
         5 . The microfluidic element according to  claim 4 , wherein the mixing channel is so shaped that the distance of the outlet opening from the axis of rotation is greater than the distance of the inlet opening from the axis of rotation. 
     
     
         6 . The microfluidic element according to  claim 1 , further comprising a capillary stop which forms a flow resistance for the liquid flowing from the mixing channel into the output channel in such a manner that spontaneous emptying of the mixing channel into the output channel is prevented until the flow resistance is overcome by an external force. 
     
     
         7 . The microfluidic element according to  claim 6 , wherein the external force is a centrifugal force generated by rotation of the microfluidic element and/or a pressure force which acts on the liquid in the mixing channel. 
     
     
         8 . The microfluidic element according to  claim 6 , wherein the capillary stop is formed by a geometric valve, which includes a primary section and a secondary section downstream from the primary section in the flow direction, the cross-sectional area of the primary section being smaller than the cross-sectional area of the secondary section. 
     
     
         9 . The microfluidic element according to  claim 6 , wherein the capillary stop includes a channel section having at least one hydrophobic channel wall. 
     
     
         10 . The microfluidic element according to  claim 1 , wherein the reagent is contained in the mixing channel in dried form. 
     
     
         11 . The microfluidic element according to  claim 1 , wherein the reagent is contained in the mixing channel in lyophilized form. 
     
     
         12 . The microfluidic element according to  claim 1 , wherein the outlet opening is positioned from the middle of the total length of the mixing channel at a distance that is at most 20% of the total length of the mixing channel. 
     
     
         13 . The microfluidic element according to  claim 1 , wherein the inlet opening is positioned from one end of the mixing channel at a distance that is at most 20% of the total length of the mixing channel. 
     
     
         14 . The microfluidic element according to  claim 1 , wherein the volume of the mixing channel is larger than the volume of the output channel. 
     
     
         15 . The microfluidic element according to  claim 1 , wherein the mixing channel has a rectangular cross-section. 
     
     
         16 . A method for providing a homogeneous thoroughly mixed liquid comprising:
 providing a microfluidic element having a substrate and a channel structure, wherein the channel structure includes an elongate mixing channel and an output channel, wherein the mixing channel has an inlet opening and an outlet opening in fluid communication with the output channel, and wherein the outlet opening is located closer to the middle of the length of the mixing channel than the inlet opening;   allowing a flow of liquid through the inlet opening into the mixing channel;   dissolving a reagent contained in the mixing channel;   exerting a force on the liquid in the mixing channel; and   allowing the liquid to flow into the output channel through the outlet opening of the mixing channel so that thorough mixing of the liquid and the reagent occur.   
     
     
         17 . The method according to  claim 16 , wherein the mixing channel has a feed section between the inlet opening and the outlet opening and a complementary section, downstream from the outlet opening in the flow direction and opposite to the inlet opening, wherein the method further comprises flowing partial volumes from the feed section and the complementary section of the mixing channel through the outlet opening into the output channel such that mixing of the two liquid partial volumes is supported by exertion of the force on the liquid. 
     
     
         18 . The method according to  claim 16 , wherein the exerted force is a centrifugal force which is generated by rotating the microfluidic element. 
     
     
         19 . The method according to  claim 16 , wherein the microfluidic element is a test carrier and the channel structure is a sample analysis channel, which comprises a sample inlet opening and a measuring zone.