Method of depositing a substance on a substrate

A method of depositing one or more allergens onto a substrate, comprising:

• providing a substrate at a distance from a conducting spraying nozzle, said spraying nozzle having an outlet;
• providing a liquid composition containing the one or more allergens to the spraying nozzle at a flow rate of from 3 to 50 mL/h;
• generating electrically charged liquid droplets from the liquid composition between the outlet of the spraying nozzle and the substrate, by providing compressed gas around the liquid composition flowing out of the outlet of the spraying nozzle and by providing an electric field downstream of the outlet of the spraying nozzle, wherein the compressed gas is selected from the group consisting of nitrogen, nitrous oxide, carbon dioxide, inert gas, argon, and mixtures thereof, and further wherein the compressed gas around the liquid composition is at a pressure of from 0.1 to 2 bar above atmospheric pressure;
• and
• collecting the generated liquid droplets on the substrate;
• wherein the spraying nozzle is arranged within a chamber, the compressed gas is fed to the chamber, and the liquid composition and compressed gas flow out of the chamber through an ejection opening in a conducting ejector, and
• wherein the one or more allergens are selected from the group consisting of peanut, milk, egg, walnut, cashew nut, pecan nut, pistachios, and hazelnut allergens.