Reading dry chemical arrays

Abstract

Array units and methods are provided which have constructions to reduce or take advantage of Fresnel reflection. The array units may have a substantially unreflective substrate. In one arrangement a transparent spacer layer is provided while in another an anti-reflective layer is present.

1 . An addressable array unit comprising: 
 a substantially unreflective substrate with a front surface, and a dry array on the front surface having a plurality of different chemical features;    wherein the features extend 80 nm to 250 nm from the front surface.    
     
     
         2 . An addressable array unit according to claim  34  wherein the features extend 100 nm to 200 nm from the front surface.  
     
     
         3 . An addressable array unit comprising: 
 a substantially unreflective substrate with a front surface and a dry array on the front surface having a plurality of different chemical features;    wherein the substrate includes a transparent anti-reflection layer extending from the front surface.    
     
     
         4 . An addressable array unit according to claim  36  wherein the multiple features comprise polynucleotides of different sequences.  
     
     
         5 . An addressable array unit according to claim  36  wherein the index of refraction of the anti-reflection layer is at least 1.2 and the substrate includes a layer behind the anti-reflection layer which layer has an index of refraction higher than the anti-reflection layer and at least 1.3.  
     
     
         6 . An addressable array according to claim  36  wherein the anti-reflection layer has a thickness of 80 nm to 200 nm.  
     
     
         7 . An addressable array according to claim  39  wherein the substrate is at least 1 micrometer in thickness.  
     
     
         8 . An addressable array unit according to claim  34  comprising instructions that an interrogating light of indicated wavelength should be directed from forward of the front surface onto the chemical features of the dry array.  
     
     
         9 . An addressable array unit according to claim  34  additionally comprising instructions that light emitted in response to an interrogating light should be detected at a prescribed angle.  
     
     
         10 . An addressable array unit according to claim  34  additionally comprising information on the thickness of the spacer layer.  
     
     
         11 . An addressable array according to claim  42  wherein the instructions are in the form of a machine readable code provided on the substrate or a housing carrying the substrate.