On the Progress of 3D Printed Hydrogels Through Fourier Transform Rheology

Direct ink writing (DIW) is a revolutionary additive manufacturing technique with high potential in the fabrication of hydrogels for applications ranging from tissue engineering to drug delivery and even soft robotics [1]. According to the printing process, the formulations of these hydrogels must be able to flow through small nozzles and recover the structure once deposited. Therefore, to understand the fluid and solid behavior of these complex materials under conditions similar to additive manufacturing, in support for printability assessment, the yield stress, thixotropy and viscosity of the hydrogels has being identified as the most relevant parameters [2]. To further advance in this field, we will focus on viscoelastic parameters under different shear conditions by using large amplitude oscillatory shear data (LAOS). Interpretation of the sequence of physical processes occurring in each deformation cycle might provide information on the viscous and elastic effects that develop during the printing event [3]. In order to explore the potential of LAOS as a relevant tool to quantify the limits of linear-nonlinear behavior related to printability criteria, different formulations of Carboxymethylcellulose CMC-based hydrogels containing atenolol as the active ingredient were printed and the rheological properties were characterized. The optimal printing parameters were correlated with Lissajous-Bowditch plots and Fourier transform (FT) coefficients to obtain additional qualitative and quantitative information on hydrogel dynamics during the printing processes.