1. A sample preparation method for combining reagents within a blood sample in order to detect cells using image cytometry, comprising: a. adding at least one reagent comprising a fluorochrome conjugated antibody to a microfluidic chamber having a height between approximately 5 μm and 150 μm wherein the reagent is contained in a dried hydrogel to provide a controlled release of the reagent within the chamber upon contact with the sample; b. filling the chamber with a blood sample wherein the reagent is released from the dried hydrogel into the sample between a time required to fill the chamber and a time required to stain the cells; c. distributing the hydrogel containing the reagent within the chamber such that during the time required to stain the cells the released reagent is uniformly distributed within an imaging area of the chamber; and d. releasing the reagent from the hydrogel within the chamber in order to detect blood cells in the blood sample using image cytometry.