Abstract
Bioprinting has been introduced as a new technique in tissue engineering for more than a decade. However, characteristics of bioprinted part are still distinct from native human tissue and organ in terms of both shape fidelity and functionality. Recently, the combination of at least two hydrogels or "multi-materials/multi-nozzles" bioprinting enables simultaneous deposition of both model and support materials, thus advancing the complexity of bioprinted shapes from 2.5D lattice into micro-channeled 3D structure. In this article, a perspective on the roles of second bioinks or support materials is presented and future outlook of sacrificial materials is discussed.