Researchers at the University of Wollongong and the Australian Research Council Centre of Excellence for Electromaterials Science (ACES) have developed the BioPen, a tool that allows surgeons to repair injured bones and joints by laying down customized implants during surgery with high precision and ease. This handheld 3D printer works by “drawing” a biomaterial scaffolding that encases stem cells. The composite biomaterial includes a cell-viable hydrogel, such as alginate, surrounded by an outer protective layer. As the scaffolding and stem cells are applied, the BioPen cures and sets the implant in place with an attached low-powered ultraviolet light. The process can be repeated to build the entire implant in real-time, layer-by-layer. As the wound heals, the stem cells work to restore tissue into its healthy state, and multiply and differentiate into bone, muscle, or nerve cells. The team plans on also incorporating growth factors and drugs into the mix to try to control the differentiation of the implanted stem cells and further improve recovery. The BioPen has now completed its prototyping stage, and is currently undergoing optimization for clinical trials.