Devices and methods for direct visual detection and readout of single nucleic acid molecules

A method of visually detecting a target nucleic acid in a sample, comprising the steps of:

• dividing the sample into a plurality of compartments;
• performing an amplification reaction on the divided sample to generate a reaction product;
• exposing the reaction product to an amplification indicator, wherein the amplification indicator changes its extinction coefficient more than 3% responsive to nucleic acid amplification;
• obtaining a color image of the reaction product in the plurality of compartments;
• determining a plurality of first intensities for a first color of the color image, wherein the plurality of first intensities corresponds to the plurality of compartments;
• determining a plurality of second intensities for a second color of the color image, wherein the plurality of second intensities corresponds to the plurality of compartments;
• and
• determining a ratio between the first color intensity and the second color intensity for a compartment, wherein the ratio is indicative of the presence or absence of amplified target in the compartment.