Mesoscale Large Frequency-Range Characterization of the Elastic Modulus of Poly(Vinyl Alcohol) Hydrogel Using a Control-Integrated Indentation System

Due to the desirable properties like biocompatibility and solubility in water, Poly (Vinyl Alcohol) (PVA) has been widely utilized in a broad range of areas including material research, biomedicine and pharmacy. Although its mechanical properties have been widely studied, few of the previous work has focused on its frequency dependent elastic modulus. In this paper, the frequency dependent elastic modulus of PVA samples (based on the physical crosslinking method) at mesoscale was investigated in experiments. An indentation system is designed and developed. And moreover, a recently-developed iterative-learning control technique is utilized to compensate for the hardware effect on the force-indentation measurement, and thereby, substantially increases the measurement frequency range. Then the Hertzian contact model is employed to obtain, from the measured force-indentation data, the elastic modulus of a PVA sample for the frequency range of 1 to 25 Hz.