Device generating evanescent waves, and method for the implementation thereof

A device comprising:

• a support having a wave guide enabling the propagation of light in at least one wavelength, generating evanescent waves outwards,
• means for receiving a liquid sample, configured to receive the liquid sample upon contact with the wave guide so as to impregnate the wave guide with a portion of the liquid sample, and
• actuatable means for breaking the contact between the liquid sample and the wave guide, the actuatable means comprising a member which is movable relative to the support and which comprises at least a portion of the receiving means,
• wherein the movable member is movable between a first position in which the receiving means are adapted to receive the liquid sample upon contact with the wave guide and a second position in which the receiving means are configured so that the liquid sample is no longer in contact with the wave guide.