The invention relates to a variable-focus lens comprising two opposing walls (21, 22) which are which define a space containing an isolating liquid (31) on the first wall (22) and a conductive liquid (32) which covers the isolating liquid and which comes into contact with the second wall (21). The surface (24) of the first wall (22) has high wettability for the isolating liquid and low wettability for the conductive liquid, while the surface (23) of the second wall (21) has high wettability for the conductive liquid and low wettability for the isolating liquid.