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.
Image courtesy of Qi (Kevin) Ge
Hydrogels, hydrophilic networks of polymeric chains capable of retaining a large amount of water, have been widely used in a variety of applications. Recently highly stretchable hydrogels have also been used in the filed 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.
For preparing highly stretchable and UV curable hydrogels for high resolution DLP based 3D printing, researchers have come up with a hydrogel solution that mixes self-developed high-efficiency water-soluble TPO nanoparticles as the photoinitiator with an acrylamide-PEGDA (AP) based hydrogel precursor. The TPO nanoparticles make AP hydrogels UV curable, and thus compatible with the DLP based 3D printing technology for the fabrication of complex hydrogel 3D structures with high-resolution and high-fidelity.
"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. According to researchers, the 3D 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 researchers to fabricate hydrogel 3D structures with resolutions up to 7 μm and complex geometries.
The 3D printed stretchable hydrogels show an excellent biocompatibility, which have been adopted to directly 3D print biostructures and tissues. The great optical clarity of the AP hydrogels offers the possibility of 3D printing contact lenses. More importantly, the AP hydrogels are capable of forming strong interfacial bonding with commercial 3D printing elastomers, which allows researchers to directly 3D print hydrogel–elastomer hybrid structures such as a flexible electronic board with a conductive hydrogel circuit printed on an elastomer matrix.
"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.