Reivindicaciones

1. A method of molecular self-assembly, comprising: - extruding a stream of a dope solution of polymer molecules out of a nozzle opening of a capillary into a surrounding environment of a focusing fluid miscible with the dope solution, optionally in presence of a coagulating bath; - hydrodynamically stretching the extruded stream of polymer dope solution while simultaneously and selectively extracting solvent into the focusing fluid from the dope solution by molecular diffusion; wherein polymer concentration in the dope solution at a stretched region of the stream reaches a level such that contact among polymer molecules results in molecular self-assembly of the polymer molecules; and optionally, - continuously extracting an elongated structure of self-assembled polymer molecules such as a fiber or a thread. 2. The method according to claim 1, wherein the polymer comprises amino acids, preferably wherein the polymer comprises amino acids making up from peptides of at least 5 amino acids to proteins of unrestricted size and/or wherein the polymer comprises at least one amino acid motif selected from the group consisting of: -GA-, - A<n> -, -GPG- and -GGX-, wherein n ranges from n=2 to n=20 and where X is an amino acid other than Glycine. 3. The method according to claims 1 and 2, wherein the stretching of the stream of polymer dope solution is carried out by accelerating the movement of the polymer dope solution stream relative to the surrounding environment of focusing fluid. 4. The method according to any one of the precedent claims, wherein the ratio of dope flow rate Q<d> to the focusing fluid flow rate Q<f> is less than 0.7%, preferably less than 0.2 %. 5. The method according to any one of the preceding claims, wherein the spun fiber or thread is retrieved on a take up device such as a rotating mandrel or a suction nozzle. 6. The method according to claim 5, wherein the ratio of the speed of the fiber or thread at the take up device to the speed of the focusing fluid ranges between 20 % and 500 %, preferably between 50 % and 200 %. 7. The method according to any one of the precedent claims, wherein the dope solution and the focusing fluid go through a converging nozzle or a slit in a plate and enter a coagulating bath or a tube. 8. The method according to any one of the precedent claims, wherein the dope solution and the focusing fluid go through a slit in a plate and enter a space created by two parallel plates. 9. The method according to any one of the precedent claims, wherein the nozzle opening is circular and has diameter larger than or equal to 50 nm. 10. The method according to any one of the precedent claims, wherein the distance between the end of the capillary and the opening of the nozzle or slit is at least 10 % that of the diameter of the nozzle opening. 11. The method according to any one of the preceding claims, wherein the rate of flow of the dope solution and focusing fluid flow is at least 10<-20> m<3> /s. 12. The method according to any one of the precedent claims, wherein the focusing fluid and/or the coagulating bath comprise an alcohol, acetone, an aqueous salt solution or mixtures thereof. 13. The method according to any one of the precedent claims, wherein the pH of the focusing fluid and/or the pH of the coagulating bath differs from the pH of the dope solution by more than 0.1. 14. An elongated structure such as a thread or fiber obtainable by the method as defined in any one of the preceding claims. 15. Use of an elongated structure as defined in claim 14 for producing biomaterials.