A device for the microstructured grafting of proteins onto a substrate, comprising a substrate (7), a layer comprising a polyethylene glycol and being placed on the substrate, a matrix (10) of micromirrors for propagating the light in a first pattern and for replacing the first pattern with a second pattern. The microfluidic circuit is filled so as to bring a first aqueous solution containing a first protein into contact with the layer, a first microstructured image of the first pattern being formed on the layer to photoprint the first protein on the layer, and the microfluidic circuit is adapted to replace the first aqueous solution with a second aqueous solution containing a second protein so as to bring the second aqueous solution and the layer into contact, the first pattern being replaced with the second pattern in order to photoprint the second protein on the layer.