Abstract: In a method for producing a compound of at least two polymer substrates, two polymer substrates each having a connecting surface are provided. At least one of the polymer substrates is coated with a self-assembling polypeptide, at least in the area of the connecting surface. The two polymer substrates are connected by pressing together the connecting surfaces under pressure and at a temperature corresponding to at least the glass transition temperature of the material of one of the polymer substrates at the connecting surface, wherein a diffusion of polymer chains takes place between the connecting surfaces by the self-assembling polypeptide and a solid connection is formed between the two connecting surfaces. A sealed microfluidic cartridge includes a polymer cartridge and a sealing film connected by such a method.