LAUSR

Three-dimensional (3D) printing has gained ever-increasing attention in the past decades since the invention of stereolithography in 1986.[1] This popularity is attributed to the unique advantages of this technology, which now is in fact a collection of various techniques including, but not limited to, those based on extrusion, inkjet, and light, that allow convenient patterning of target materials in the volumetric space in a fully or semi-automated manner. Yet it was not until more recently that the 3D printing technology was applied to medicine and biomedicine for the fabrication of medical devices and biological tissues for life quality enhancement.[2] While the 3D printing modalities are the foremost in determining our capacity in successful fabrication of volumetrically structured objects, the contributions of the materials, or what we term as “biomaterial inks”, are perhaps no less important if not more. These biomaterial inks have to be designed in such a way that they are not only specific to the desired applications, but also, allow high-fidelity 3D printing in the first place.[3] Examples range from inks that should minimize inflammatory responses of the host tissues, inks that should ensure activities of cells encapsulated or post-seeded, and/or inks that should provide multiple functionalities to mimic the sophisticated biological needs. This special issue on “Biomaterials Inks” is thus focused on biomaterials that are meticulously tailored for use as inks/bioinks towards 3D printing/bioprinting applications. We have collected three reviews, three progress reports, and ten research articles, which broadly cover the various important topics within the area. Kaplan et al. talk about directed hierarchical molecular assembly used towards biofabrication, including bioprinting, of the silk biomaterials (see article number 1901552). Moroni et al. then discuss an important class of bioinks, the dynamic bioinks taking advantages of the supramolecular and dynamic covalent chemistries, for applications in advanced bioprinting (see article number 1901798). Finally, Woodfield et al. go a step beyond and converse about the design principles of multicomponent hydrogel bioinks for extrusion bioprinting (see article number 1901648). Three systematic progress reports then ensue. An overview of recent progress in 3D bioprinting is first provided by Perriman et al., through discussions on bioprinting modality designs, tissue-specific applications, and bioink developments