February 22, 2018
Abstract: The compositional and microstructural complexity of biomaterials represents a materialome – a rich expression of physical properties that is produced by the presence of many material constituents and their interactions. The large parameter space but initial scarcity of many such emerging materials is a significant bottleneck to their design and development.
Microrheology can play an important role when the engineering objective is to design or characterize the rheology of biomaterials. Microrheology uses the movement of colloidal particles in a material, essentially as tiny, "embedded rheometers." The operating regime of microrheology opens a wide range of samples and conditions which may be difficult, if not impossible, to measure by conventional rheometry. From the studies of Heilbronn, Freundlich, and Seifriz in the early 20th century on, particles have been used to measure rheology in small sample volumes. Today, particle tracking, single-particle interferometry, magnetic bead, and laser tweezer microrheology typically require sample volumes between ~1 and 10 microliters.
Microrheology thus opens up many scarce and expensive materials to rheological characterization. Protein therapeutics and emerging biomaterials are just two examples with large and complex formulation spaces. Because the acquisition times are short, the small sample dimensions facilitate rapid mass and heat transfer, and the methods can harness microfluidics for sample preparation and manipulation, microrheology enables rapid screening of conditions and compositions to capture the "genome" of a material.