Abstract: The present invention relates to a method to analyse the ability of a substance (3) to cross a bilayer membrane comprising the following steps: (i) providing in a hydrophobic medium (1) a first droplet D1 of an aqueous solution AS1, wherein the droplet D1 is surrounded by a monolayer of amphiphilic molecules (2), (ii) providing in the said hydrophobic medium (1) a second droplet D2 of an aqueous solution AS2 containing the substance (3) to be analysed, wherein the droplet D2 is surrounded by a monolayer of amphiphilic molecules (2), (iii) putting the first droplet D1 and the second droplet D2 into contact so as to form a bilayer of amphiphilic molecules (2) in the contact area and to have a contact angle 2? between the two droplets D1 and D2 comprised between 10° and 180°, (iv) adding to the hydrophobic medium (1) a solvent capable of separating the droplets D1 and D2 put into contact, (v) collecting the droplet D1, and (vi) analysing the content of the droplet D1 in order to determine the presence or not of