Micro fluidic structures

Abstract

A micro fluidic system includes a substrate, and, provided on said substrate, at least one flow path interconnecting with functional means in which liquid samples can be treated by desired procedures. The flow paths are laid out to form a pattern for the transport of liquid samples to and from said functional means. These flow paths comprise a plurality of micro posts protruding upwards from said substrate, the spacing between the micro posts being small enough to induce a capillary action in a liquid sample applied anywhere within any of said flow paths, so as to force said liquid to move from where said liquid sample was applied.

1 . A method for measuring the amount of analyte in a biological sample, the method comprising the steps of:
 providing a micro fluidic system, the system comprising:
 a substrate having a non-porous surface; 
 a plurality of microposts protruding from the non-porous surface of the substrate, said microposts defining at least one open flow path in which liquid samples can be treated by desired procedures, wherein the at least one flow path is laid out for transport of liquid samples, the at least one flow path extending in a lateral direction which is transverse to the protruding microposts, wherein cross sections of the microposts and the center to center spacing between each of the microposts spontaneously induces a passive capillary action in a liquid sample applied to the at least one flow path, so as to force the liquid to move laterally away from where the liquid sample was applied, the microposts further including antibodies having an affinity for the analyte in the sample; 
 a sample receiving area disposed prior to the at least one flow path and fluidly connected therewith; and 
 a sample collecting sink disposed after the at least one flow path on the substrate and fluidly connected with the at least one flow path, the sample collecting sink having an area which is larger than the area of the at least one flow path extending from the sample receiving area, the sink having a plurality of microposts protruding from the substrate surface, the sink microposts having cross sections and center to center spacing between each of said microposts that further induce capillary flow from the at least one flow path to the sample collecting sink; 
 applying the biological sample containing analyte to the sample receiving area; 
 flowing the sample through the at least one flow path, whereby the analyte in the sample is captured by the antibodies; and 
 measuring the amount of analyte by immunological means. 
   
     
     
         2 . The method according to  claim 1 , including the step of providing functional means comprising one or more of chemical reactors, separation means, heating means, means for irradiation with electromagnetic radiation, magnetic means for trapping magnetic components of said liquid within said functional means, electrodes for applying voltage to the liquid over a selected region, or any other device or means for chemically, biologically or physically treating liquid samples. 
     
     
         3 . The method according to  claim 1 , wherein the substrate is provided with grooves having a bottom surface and side walls, and wherein the at least one flow path includes the micro posts protruding from the bottom surface of the grooves. 
     
     
         4 . The method according to  claim 3 , including the step of providing a top or lid covering the at least one flow path, wherein the top or lid does not significantly contribute to the capillary action in said at least one flow path. 
     
     
         5 . The method according to  claim 4 , including the step of providing the lid or top with access openings for enabling introduction of reagents, gas, liquids, samples into the at least one flow path. 
     
     
         6 . The method according to  claim 1 , including the step of grouping the protruding microposts along the at least one flow path in adjacent segments so as to provide a spacing or discontinuity between such segments, the discontinuity having a finite distance, which is large enough to prevent capillary flow between the segments, thereby providing a flow stop. 
     
     
         7 . The method according to  claim 6 , including the step of providing means for applying energy to the one or more selected segments so as to induce a forced transport across the flow stop. 
     
     
         8 . The method according to  claim 7 , wherein the energy applying means is selected from at least one of the group consisting essentially of a pressure pulse generator, ultrasound generator, and an electromagnetic radiation means. 
     
     
         9 . The method according to  claim 6 , comprising the step of providing means for applying liquid to the discontinuity in order to provide a bridge across said discontinuity so as to induce a flow there across. 
     
     
         10 . The method according to  claim 1 , including the step of providing a chemical, biologic or physical functionality to the surfaces of the microposts wherein the functionality is defined by the microposts having at least one of the group consisting essentially of chemically reactive groups, substances with biological affinity, hydrophilic groups, hydrophobic structures, and positively and/or negatively charged groups on their surfaces. 
     
     
         11 . The method according to  claim 10 , wherein the step of providing a functionality includes the step of providing the functionality to the micro posts over the entire at least one flow path or limiting the functionality to a discrete region or portion of the at least one flow path. 
     
     
         12 . The method according to  claim 11 , wherein said properties are selected from the micro post diameter, height, shape, cross section, surface coating, number of micro-posts per unit area, wetting behavior of the micro-post surface, or a combination thereof. 
     
     
         13 . The method according to  claim 1 , including the step of providing particles within the at least one flow path. 
     
     
         14 . The method according to  claim 13 , including the step of chemically or physically bonding particles to the substrate, or mechanically trapping the particles within a region comprising a plurality of the protruding microposts. 
     
     
         15 . The method according to  claim 1 , including the step of providing the at least one flow path with integrated zones or delimited surfaces containing electrodes or other means for electrical manipulation of liquids and/or reagents. 
     
     
         16 . The method according to  claim 1 , including the step of providing the at least one flow path with integrated zones or delimited surfaces, the zones or surfaces containing at least one of optical elements or other means for transmitting, focusing, reflecting or absorbing light, magnetic functionalities or means for manipulation and/or detection of magnetic substances, and means for the regulation of the temperature in the zone, e.g., heating or cooling said zone.