PHOTO-GUIDED SHAPE TRANSFORMATION OF COMPOSITE HYDROGEL SHEETS

Abstract

Shape-changing hydrogel material has numerous potential applications in biomimetics, soft robotics, biomedicine, etc. Light as a clean energy source can be remotely delivered to material with high spatial and temporal resolution, which brings new controllability to shape-transformation of hydrogel material. However, the current strategy of using light to control deformation of hydrogel is limited. This dissertation aims to develop new approaches to program shape-transformation of hydrogel material by using light.

First, I developed a simple and efficient approach to re-program shape-transformation of composite hydrogel sheet with homogeneously distributed silver nanoparticle. By modulating light irradiation pattern, the same hydrogel sheet transformed to multiple distinct geometries, which were verified by finite element method.

Secondly, I developed a simple and reliable approach to pattern various types of photo-thermal converting nanoparticles in hydrogel sheet. The approach enables nanoparticle patterning in both lateral and thickness-direction of hydrogel, which cannot be readily achieved by other approaches such as microcontact printing and photo-lithography.

Thirdly, I explored shape transformation of composite hydrogel sheet with spatially patterned plasmonic gold nanoparticles fabricated by using the approach mentioned above. The same patterned composite hydrogel sheet can be designed to exhibit distinct shape transformation modes, highly depending on light irradiation direction, which has not been reported before.

Fourthly, I studied shape transformation of composite hydrogel sheet spatially patterned with erasable and rewritable iron oxide nanoparticles. The same hydrogel sheet was re-programmed to exhibit various distinct shape transformations by changing nanoparticle pattern. This provides a new method to reprogram shape transitions of hydrogel material by using external light source. In addition, a hydrogel tube was also readily patterned with iron oxide nanoparticles and its deformation was studied as well.

Lastly, I developed a simple and general approach to fabricate multifunctional composite hydrogel tube. The hydrogel tube was formed via self-rolling of 2D hydrogel sheet after releasing stress introduced during photo-polymerization. The introduced magnetic nanorod brought multi-functionality to the hydrogel tube. The self-rolled tube was used to load, transport and release cargo manipulated by capillary force, magnet and light, respectively.

This dissertation provides a new, simple and efficient toolset to program and re-program shape transformation of composite hydrogel material by using external light. It is believed that the toolset and concept developed in this dissertation can be applied to other light-responsive hydrogel material.