A device for trapping particles contained in a liquid (L) placed in a tank, characterized in that it comprises a substrate that is transparent at a working wavelength, a thin layer of material with non-linear optical properties that are reversible at the working wavelength and which is fixed to a first face of the transparent substrate to form all or part of at least one wall of the tank, a device for forming an optical trap which comprises a laser source which emits a laser beam and means for forming a waist of the laser beam, the laser beam being incident upon that face of the transparent substrate that lies on the opposite side to the first face and the waist of the laser beam being formed in the thin layer, an evanescent electromagnetic field forming at the surface of the thin layer.