Nano-structured materials can be manipulated through the application of shear fields. The image above shows the orientation of a crystalline system of polymeric micelles under simple shear deformation. This induces a disorder – order transition where the crystal structure continues to evolve depending on the shear field that is being applied. Small perturbations (linear rheology) and large shear deformation (non-linear) is also used to mechanically probe rheological parameters that can be related to the structure of the samples.
We are identifying the relationship between the structure and mechanical properties of fibrin networks. Fibrin, a highly organized filamentous protein, is the major structural component of a blood clot. The shear modulus of a fibrin network can easily exceed 1000 Pa despite the fact that the material contains more than 99% water. They also show a high degree of reversible strain-hardening, a property that is common in biological networks but unusual in synthetic materials. Despite its importance and relevance to trauma and to numerous diseases (e.g. hemophilia and stroke), the relationship between the properties and the structure of blood clots under mechanical deformation remains unknown. We use rheology with in-situ structural probes to directly examine these materials as they are being deformed. Deciphering the origin of these properties will also allow us to emulate them in synthetic analogs such as biomaterials and scaffolds for tissue engineering.