Gerald G. Fuller, Stanford University, Dept. of Chemical Engineering, Stanford, CA 94305-5025 and An J. Goffin, Chemical Engineering, Stanford University, 381 North South Mall, Stanford, CA 94305.
Collagen layers residing at the air/water interface are manipulated by interfacial flows to induce orientation of this protein. By spreading collagen at the interface, the kinetics of fibril formation can be controlled and this is monitored directly using interfacial rheological measurements. The orientation of the fibrils is also measured in situ using dichroism measurements during the application of flow. It is established that the fibers undergo an isotropic-to-nematic phase transition upon compression of the films above a critical surface pressure. The advantage of taking the system into the nematic phase is that flow-induced orientation remains in the films for a sufficiently long time so that Langmur-Blodgett deposition processes can to accomplished. The resulting transferred films of highly oriented collagen fibrils are demonstrated to provide "contact guidance" of mammalian cells onto which they are cultured.