Controlled dispensing of samples onto substrates

Abstract

Methods for dispensing a fluid sample on a substrate include obtaining an image of a sample applicator in proximity to the substrate, where the image includes a first image of the sample applicator and a second image of the sample applicator, determining a height of the sample applicator relative to a surface plane of the substrate based on a distance between common portions of the first and second images, and dispensing the fluid sample onto the substrate using the sample applicator, where the dispensing includes: translating the sample applicator, translating the substrate, or translating both the sample applicator and the substrate to effect a relative translation between the sample applicator and the substrate; and maintaining the sample applicator within 2 microns of a target height relative to the surface plane of the substrate during the translating.

What is claimed is: 
     
         1 . A method for preparing a sample on a substrate, the method comprising:
 obtaining an image of a sample applicator in proximity to the substrate, the image comprising a direct image region corresponding to the sample applicator and a first reflected image region corresponding to an image of the sample applicator reflected from a surface of the substrate;   determining a position of an edge of the sample applicator in the direct image region;   determining a position of a reflected edge of the sample applicator in the first reflected image region;   determining a distance between the edge of the sample applicator and the reflected edge of the sample applicator;   determining the position of the sample applicator relative to a surface of the substrate based on the distance between the edges; and   dispensing the sample onto the substrate using the sample applicator, wherein during the dispensing the position of the sample applicator relative to the substrate is maintained.