A gradient Laponite-crosslinked nanocomposite hydrogel with anisotropic stress and thermo-response

A gradient Laponite (Lap)-crosslinked nanocomposite (NC) hydrogel was fabricated by a facile electrophoresis method based on colloidal property of Lap, as well as interaction between Lap and thermo-responsive monomers. TGA, FTIR, SEM and TEM were used to characterize the gradient structure. The gradient NC hydrogel exhibited both gradient distribution of Lap and thermo-responsive polymers under the induction of direct current electric field (DC-EF). The gradient NC hydrogel showed anisotropic mechanical properties and gradient thermo-response along the direction of DC-EF. The mechanical strength of the gradient NC hydrogel increased by 38% compared with isotropic NC hydrogel. An increase in Lap content would improve the mechanical property and extend the strength range in different locations of the gradient hydrogel. Meanwhile, the compressive strength of the gradient NC hydrogels can also be adjusted in the range of 117-1774 kPa by changing the concentration of Lap. The work enabled the gradient NC hydrogels to apply in the field of tissue engineering and provided a new insight into development of novel bionic materials.