It’s tedious and tiring to move the 3D printing pen through the motions to build simple parts, but that’s the whole gimmick here. What’s wild is how good the results are.

The ink can be spread into a cut of any shape using a 3D-printing pen, and in mice, the technology nearly completely repaired wounds in just 12 days.

But researchers publishing in ACS Applied Materials & Interfaces have developed a wound-healing ink that can actively encourage the body to heal by exposing the cut to immune-system vesicles. The ink ...