Haake mars 3 rheometer

Mechanical properties were analyzed by a HAAKE MARS III rheometer (Thermo Scientific) with a parallel plate measuring geometry. Hydrogel samples (350 µL) were measured at a constant temperature of 20 °C, a strain of 1%, and a frequency of 1 Hz, if not stated otherwise. The gap was set to 1.8 mm.

Rheological measurements were performed using an HAAKE MARS III rheometer (Thermo Scientific) operating in oscillatory shear conditions. The experimental settings used to characterize chitosan gels were the following: titanium plates with 2° cone/plate geometry (Ø = 35 mm) and a gap of 0.105 mm. In the case of the on-rheometer gelation, time sweep experiments were carried out in strain-controlled conditions, with the strain, γ, of 3% kept constant throughout the experiment; frequency, ν, of 1 Hz; time of 10,800 s; T = 60 °C. The values of storage G′ (elastic response) and loss G″ (viscous response) moduli were recorded as a function of time. Mechanical spectra were recorded at T = 37 °C under oscillatory shear conditions, with the constant applied stress, τ, of 1 Pa (well within the linear viscoelasticity range) in the frequency range 0.01–100 Hz. At the end of the frequency sweep measurements, stress sweep experiments were performed, with ν = 1 or 0.1 Hz, respectively, stress range 1 < τ < 1000 Pa and T = 37 °C.

The oscillatory rheological experiments of the optimized hydrogels were performed using a HAAKE MARS III rheometer (Thermo Scientific, Karlsruhe, Germany) with a 35 mm diameter cone (2° angle) and a plate rheometer equipped with a Peltier unit to control the temperature [52 (link)]. The desired gap between cone and plate was set to 0.105 mm. To identify the linear viscoelastic (LVE) region, the strain sweep experiments were carried out from 0.10% to 1000% strain amplitude at a constant frequency of 1 Hz and 37 °C. The frequency sweeps were conducted in a frequency ranging from 0.1 to 100 Hz within the LVE range (10% deformation). The gelation time was determined by time sweeps at a fixed temperature of 37 °C with a frequency of 1 Hz and 10% strain, while the gelation temperature was investigated by increasing temperature from 25 to 40 °C at a heating rate of 1 °C/min. The storage modulus (G’) and the loss modulus (G’’) were recorded.