Developments in characterizing soft matter

Soft matter—also known as complex fluids—is a field of growing interest and importance, spanning many classes of materials, including polymers, biopolymers, colloids, and liquid crystals. Different approaches for microstructural characterization are more appropriate than those used for hard (and usually fully crystallized) materials such as metals and inorganic materials because of the time and length scales involved. This article discusses a range of techniques applicable to the characterization of soft matter, including environmental scanning electron microscopy (SEM) and microrheology. The former offers two key advantages for this class of material over conventional SEM because it requires neither a high vacuum—which is a problem for hydrated samples—nor that an insulator be coated with a conductive material. Microrheology is well suited to small volumes of fluid with low moduli that may be heterogeneous; it is capable of measuring gelation in real time.