On-line observation of hydrogels during swelling and LCST-induced changes

A new technique for the online observation of rheological data of hydrogels during experiments involving significant volume changes is proposed. In order to accommodate for large volume changes, the gap has to be force controlled and continuously adjusted to the current sample height. Furthermore, the force control also has to ensure the adhesion of the sample to the geometry. For smaller volume changes, it is also possible to employ experiments with constant gap. Due to the volume change, the sample is not clearly defined with respect to the open surfaces in a parallel plate geometry, which leads to too high values, which, however, can be compensated for properly.