Fig. 1. Working principle of microfluidic staining of FS.

(a) Once the frozen sample preparation is completed, the sample is clamped using a gasket to the Microfluidic Tissue Processor (MTP) to form a reaction chamber of 17x17 mm², after which the system is ready for fast IHC staining. Microfluidic channels deliver reagents to and from the reaction chamber. Staining takes place only in the chamber (b) Schematic cross-section of the MTP clamped to the tissue slide. Inside the reaction chamber, reagents are sequentially delivered and washed over the surface of the tissue section. The MTP enables a fast fluidic exchange on a one-second timescale, while keeping reagent exposure times uniform throughout the whole tissue surface. (c) Schematics of the laboratory setup used for the experiments: (i) 50 mL reservoirs are used for common reagents, namely PBS, DIW, DAB, and hematoxylin; (ii) 1.5 mL Eppendorf tubes are used to load specific reagents, such as antibodies, and blocking solutions; (iii) a computer-operated valve-manifold called Reagent Delivery System (RDS) allows for the selection of the reagents that are flushed into the chamber of reaction; (iv) MTP/ tissue sample staining chamber. (d) Picture of the prototype used for the experiments. The inset (i) shows the mechanism of manual insertion of the MTP in the machine.