Integral field spectroscopy is a modern technique used in Astronomy to obtain simultaneous spectral information of all points in a bidimensional field of view. This communication presents the preliminary design of a multi-slit image slicer to be coupled to the spectrographs of the 4 meters aperture European Solar Telescope. This integral field unit will provide the observation of an 80 arcsec2 field of view, rearranged into 8 slits of 200 arcsec length by 0.05 arcsec width. Different optical design alternatives with diffraction limited optical quality, as well as the design of a prototype for the GREGOR solar telescope, are presented.