Ultrasound response of viscoelastic changes of cellulose hydrogels triggered with Sono-deviced rheometer

Sono-deviced rheometer,which enabled viscoelastic properties under ultrasound operation, was used to investigate for cellulosic hydrogels. The viscoelastic behavior was compared in cellulosic hydrogels prepared at 0.5, 1 and 2 wt% concentration in the DMAc/LiCl solution. The sono-deviced equipment could measure the effect of changes in storage modulus G' and loss modulus G" under 43 kHz ultrasound exposure. It was noted that the 43 kHz ultrasound significantly changed the values of the G', meaning that the hydrogel was soften under the exposure within few seconds. When the ultrasound exposed 50 W of the out-put power at 1% strain, the G' value of 4.2x10⁴ Pa was reduced to 4.0x10³ Pa during 5 min of the US interval. The declined lowering value of G' then returned to the original moduli value when ultrasound was stopped. The values of both G' and G" values were measured at applied strain % during viscoelastic measurements of the cellulosic hydrogels without and with ultrasound exposure. The comparison indicated that the ultrasoundhas reinforced the effect of the mechanical deformationof the hydrogel structureat the smaller mechanical strain values appliedduring the ultrasound operation. The ultrasound soften effect onthe viscoelastic change efficiently occurred in the 0.5 wt% sample and easily induced the structural deformation probably due to the breakage of hydrogen bonds in the cellulose hydrogels.