Three-dimensional (3D) bio-printing is a novel engineering technique by which the cells and support materials can be manufactured to a complex 3D structure. Compared with other 3D printing methods, 3D bio-printing should pay more attention to the biocompatible environment of the printing methods and the materials. Aimed at studying the feature of the 3D bio-printing, this paper mainly focuses on the current research state of 3D bio-printing, with the techniques and materials of the bio-printing especially emphasized. To introduce current printing methods, the inkjet method, extrusion method, stereolithography skill and laser-assisted technique are described. The printing precision, process, requirements and influence of all the techniques on cell status are compared. For introduction of the printing materials, the cross-link, biocompatibility and applications of common bio-printing materials are reviewed and compared. Most of the 3D bio-printing studies are being remained at the experimental stage up to now, so the review of 3D bio-printing could improve this technique for practical use, and it could also contribute to the further development of 3D bio-printing.
Bionic untethered micro-nano robots, due to their advantages of small size, low weight, large thrust-to-weight ratio, strong wireless mobility, high flexibility and high sensitivity, have very important application values in the fields of biomedicine, such as disease diagnosis, minimally invasive surgery, targeted therapy, etc. This review article systematically introduced the manufacturing methods and motion control, and discussed the biomedical applications of bionic untethered micro-nano robots. Finally, the article discussed the possible challenges for bionic untethered micro-nano robots in the future. In summary, this review described bionic untethered micro-nano robots and their potential applications in biomedical fields.