Hydrogels, hydrophilic networks of polymeric chains capable of retaining a large amount of water, have been widely used in a variety of applications. Recent advances in highly stretchable hydrogels have extended their applications into the fields of soft robotics, transparent touch panels and other applications requiring large deformation.
However, traditional fabrication methods, which mainly rely on molding and casting, confine the scope of applications due to the limited geometric complexity and the relatively low fabrication resolution. Along with recent rapid developments in 3D printing, various attempts have also been made to use 3D printing to fabricate hydrogel structures with complex geometries including vascular networks, porous scaffolds, meniscus substitutes and others. Nevertheless, existing 3D printed hydrogels do not have high printing resolution, high geometric complexity as well as high stretchability, which makes them unsuitable for many applications.
Recently, researchers from the Singapore University of Technology and Design (SUTD) Digital Manufacturing and Design (DManD) Centre and the Hebrew University of Jerusalem (HUJI) have developed a family of highly stretchable and UV curable hydrogels that can be stretched by up to 1300%, and are suitable for UV curing based 3D printing techniques. These have been adopted to fabricate hydrogel structures that require high printing resolution and high geometric complexity. Details of this work appeared in the April 2018 issue of Journal of Materials Chemistry B and it was also featured on the front cover.
"We have developed the most stretchable 3D printed hydrogel sample in the world," said Assistant Professor Qi (Kevin) Ge from SUTD's Science and Math Cluster, who is one of the co-leaders of this project. He added: " The printed hydrogel sample can be stretched by up to 1300%. At the same time, the compatibility of these hydrogels with digital light processing-based 3D printing technology allows us to fabricate hydrogel 3D structures with resolutions up to 7 μm and complex geometries."
"The printed stretchable hydrogels show an excellent biocompatibility, which allows us to directly 3D print biostructures and tissues. The great optical clarity of these hydrogels offers the possibility of 3D printing contact lenses. More importantly, these 3D printable hydrogels can form strong interfacial bonding with commercial 3D printing elastomers, which allows us to directly 3D print hydrogel-elastomer hybrid structures such as a flexible electronic board with a conductive hydrogel circuit printed on an elastomer matrix," said Professor Ge.
"Overall, we believe the highly stretchable and UV curable hydrogels, together with the UV curing based 3D printing techniques, will significantly enhance the capability of fabricating biostructures and tissue, contact lenses, flexible electronics, and many other applications," said Professor Shlomo Magdassi who is a co-leader of this project at HUJI.
This work is funded by the Singapore National Research Foundation (NRF).