Capillary barriers for staged loading of microfluidic devices

Abstract

Various aspects of the present disclosure are directed toward methods and apparatuses for interacting a first liquid and a second liquid in one or more fluidic channels of a capillary structure. The methods and apparatuses can include providing at least one capillary barrier that positions a meniscus of the first liquid at a fluid-interface region using capillary forces within the capillary structure. Additionally, a path is provided along one of the channels for the second liquid to flow toward the fluid-interface region. Additionally, gas pressure is released, via a gas-outflow port, from the fluid-interface region while flow of the first liquid is arrested. Further, the first liquid and the second liquid contact in the fluid-interface region with the capillary barrier holding the first liquid at the fluid-interface region.

What is claimed is: 
     
         1 . A method for interacting a first liquid and a second liquid in one or more fluidic channels, the method comprising:
 providing a capillary barrier configured and arranged to position a meniscus of the first liquid at a fluid-interface region using capillary forces;   providing a path along one of the channels for the second liquid to flow toward the fluid-interface region;   providing an escape path through which liquid can escape from the fluid-interface region, the escape path including a fluid-flow limiter, connected to a gas-outflow port, configured and arranged to limit a volume flow rate of fluid;   releasing gas pressure, via the escape path and the gas-outflow port, while flow of the first liquid is arrested; and   causing the first liquid and the second liquid to contact in the fluid-interface region with the capillary barrier holding the first liquid at the fluid-interface region.   
     
     
         2 . The method of  claim 1 , wherein the second liquid is driven toward the fluid-interface region by air pressure gradients, and the path for the first liquid to flow and the path for the second liquid to flow are microfluidic channels supported by a microfluidic chip that includes circuitry configured and arranged for receiving data indicative of an interaction between the first liquid and the second liquid, and wherein the fluid-flow limiter is further configured and arranged to mitigate fluid loss through a path in which the gas-outflow port permits gas to outflow. 
     
     
         3 . The method of  claim 1 , further including a protrusion in the form of a triangular post configured and arranged at an upstream portion of the fluid-interface region and on a wall of the path for the first liquid to flow toward the fluid-interface region. 
     
     
         4 . The method of  claim 1 , wherein the path for the first liquid to flow and the path for the second liquid to flow are microfluidic channels, and an intersection of the microfluidic channels form a junction near the gas-outflow port. 
     
     
         5 . The method of  claim 1 , wherein while in a state in which the capillary barrier has arrested flow of the first liquid, releasing gas pressure, via the gas-outflow port, from the fluid-interface region while the second liquid is flowing toward the fluid-interface region. 
     
     
         6 . The method of  claim 1 , wherein the capillary barrier arrests flow of the first liquid while the first liquid is moving toward the fluid-interface region under a nominal degree of fluid pressure, wherein the capillary barrier is configured and arranged to provide a meniscus barrier for the first liquid for and relative to the nominal degree of fluid pressure. 
     
     
         7 . The method of  claim 1 , wherein at least one of the first liquid and the second liquid includes at least one of DNA, RNA, proteins and cells. 
     
     
         8 . The method of  claim 1 , wherein the capillary structure is secured to a microfluidic chip that includes circuitry that receives data indicative of an interaction between the first liquid and the second liquid and that performs microfluidics analysis of quantification and quality control of one or more of DNA, RNA, proteins and cells in at least one of the first liquid and the second liquid. 
     
     
         9 . The method of  claim 1 , further including a microfluidic chip supporting the capillary structure and including circuitry that receives data indicative of an interaction between the first liquid and the second liquid, wherein the circuitry performs preparative electrophoresis analysis of separation and extraction of DNA fragments in at least one of the first liquid and the second liquid. 
     
     
         10 . The method of  claim 1 , further including a microfluidic chip supporting the capillary structure and including circuitry that receives data indicative of an interaction between the first liquid and the second liquid, wherein the circuitry is configured and arranged to target nucleic acid enrichment in at least one of the first liquid and the second liquid. 
     
     
         11 . An apparatus comprising:
 a capillary structure including a first microfluidic channel or reservoir presenting a first liquid near a fluid-interface region and including a second microfluidic channel for guiding a second liquid toward the fluid-interface region,   a capillary barrier configured and arranged to position a meniscus of the first liquid at the fluid-interface region using capillary forces;   a gas-outflow port configured and arranged to release gas pressure while flow of the first liquid is arrested; and   an escape path through which liquid can escape from the fluid-interface region, the escape path including a fluid-flow limiter, connected to the gas-outflow port, configured and arranged to limit a volume flow rate of fluid.   
     
     
         12 . The apparatus of  claim 11 , wherein the first fluid and the second fluid are loaded without using a vacuum. 
     
     
         13 . The apparatus of  claim 11 , wherein the first microfluidic channel and the second microfluidic channel are formed from polydimethylsiloxane (PDMS). 
     
     
         14 . The apparatus of  claim 11 , wherein the first microfluidic channel and the second microfluidic channel respectively include hydrophobic surfaces. 
     
     
         15 . The apparatus of  claim 11 , wherein an upstream portion of the capillary barrier is at least in part defined by a change in cross-sectional area for the first liquid flowing in the capillary structure, the change being sufficient to arrest flow of the first liquid flowing toward the fluid-interface region. 
     
     
         16 . The apparatus of  claim 11 , wherein the surface forces at an upstream portion of the capillary barrier are defined by a change in cross-sectional area for the first liquid flowing in the capillary structure. 
     
     
         17 . The apparatus of  claim 11 , further including a microfluidic chip secured as part of the capillary structure, the microfluidic chip including circuitry configured and arranged to receive data indicative of an interaction between the first liquid and the second liquid and to perform microfluidics analysis of quantification and quality control of one or more of DNA, RNA, proteins and cells in at least one of the first liquid and the second liquid. 
     
     
         18 . The apparatus of  claim 11 , further including a microfluidic chip supporting the capillary structure and including circuitry configured to receive data indicative of an interaction between the first liquid and the second liquid, wherein the circuitry is further configured to perform preparative electrophoresis analysis of separation and extraction of DNA fragments in at least one of the first liquid and the second liquid. 
     
     
         19 . The apparatus of  claim 11 , further including a microfluidic chip supporting the capillary structure and including circuitry configured to receive data indicative of an interaction between the first liquid and the second liquid, wherein the circuitry is configured and arranged to target nucleic acid enrichment in at least one of the first liquid and the second liquid. 
     
     
         20 . A method for interacting a first liquid and a second liquid in one or more fluidic channels, the method comprising:
 providing a capillary barrier configured and arranged to position a meniscus of the first liquid at a fluid-interface region using capillary forces;   providing a path along one of the channels for the second liquid to flow toward the fluid-interface region;   providing an escape path for escaping fluid to exit from the region between the first and second liquid;   providing, within the escape path, a fluid-flow limiter configured and arranged to limit the volume flow rate of the escaping fluid; and   causing the first liquid and the second liquid to contact in the fluid-interface region.   
     
     
         21 . The method of  claim 20 , further including a gas-outflow port connected to the escape path, wherein the first liquid and the second liquid merge in the fluid-interface region with the capillary barrier holding the first liquid at the fluid-interface region and with gas pressure being released via the gas-outflow port.