2026 年 94 巻 8 号 p. 087003
Rheo-impedance is the joint use of a rheological measurement and an electrical, electrochemical, or dielectric measurement to follow how a soft material or complex fluid reorganizes as it is processed or as it changes state. The two answer different questions about the same sample: rheology reports how the material flows and how stiff or elastic it is, while impedance, conductivity, and dielectric data report how well charge moves through it and what is happening at its interfaces. Because the mechanical and the electrical responses often depend on different parts of the microstructure, and need not change at the same moment, measuring both can separate states that look identical to either method alone. In this review, “rheo-impedance” is used as an organizing term rather than the name of a single standardized technique. The literature is grouped into three configurations—simultaneous, separate-but-linked, and correlation-based—and five material classes: carbon-black and conductive-colloid suspensions, lithium-ion battery slurries, polymer-electrolyte fuel-cell catalyst inks, gelation and stimuli-responsive systems, and drying, curing, and sintering. Four observations recur across these systems: the mechanical and electrical changes may be linked to the same process yet appear at different stages; a stiffer structure does not necessarily carry charge better; the structure present under flow is not always the one retained after processing; and both agreement and disagreement between the two responses can be informative. Throughout, we try to separate what has been shown experimentally from what is still system-dependent interpretation or future prospect. The main open problems are the ambiguity of equivalent-circuit interpretation, the limited transfer of descriptors between the flowing and the finished state, and the absence of standard geometries, frequency windows, and reporting conventions.
