Original research

Shape-changing biomaterials

Shape transformation is widely observed in nature, commonly in plants and invertebrate animals. It has recently become a source of inspiration for the creation of new types of responsive, multifunctional, and reconfigurable materials. 

Transformation of an easy-to-prepare 2D sheet to a prescribed 3D one in response to an external trigger could find great promise for applications in tissue engineering, drug delivery, sensing, and soft robotics.

To this end, we took two poly(ethylene glycol diacrylate), a bioinert polymer, with differing molecular weights and made two thin hydrogel sheets laid on top of one another on a glass substrate via a thermally activated sacrificial layer. Once this sacrificial layer is removed, the hydrogel bilayer rolled up to a tube within seconds. This rolling is a physical phenomenon, originally described back in 1909. Two sheets deposited on one another develop stress, which can cause bending of the bilayer. In our design, the difference in the degree of swelling of each layer with water caused the driving stress. Towards its application in healthcare, we showed that such tubes can encapsulate muscle cells and can thus serve as implantable tissue building blocks.

This conceptual design can represent an advantageous strategy for protecting cells from the surrounding environment of the host tissue, especially from the immune system, while providing an appropriate microenvironment for adhesion and proliferation of muscle cells, in the alternative of exposing cells to possible light‐induced DNA damages or other toxicity issues. This system can also be used to encapsulate other cell types and gives insights into the self‐folding smart materials and their biomedical use.

Reference to the original article: Vannozzi and Yasa et al. Macromolecular Bioscience, 2018.