A groundbreaking advancement in 3D printing within the human body has been achieved by a collaborative team of researchers from Duke University and Harvard Medical School. Their innovative approach involves utilizing ultrasound waves to solidify an injectable biocompatible ink, as detailed in a recent paper published in the journal Science.

Building upon a previously developed photo-sensitive ink that hardens when exposed to light, the researchers sought to overcome the limitation of light penetration, which extends only a few millimeters into the patient’s tissue. The new technique, termed “deep-penetrating acoustic volumetric printing” (DVAP), leverages the sono-thermal effect, where soundwaves are absorbed, increasing the temperature and subsequently solidifying the ink.

According to coauthor Junjie Yao, an associate professor of biomedical engineering at Duke, “Ultrasound waves can penetrate more than 100 times deeper than light while still spatially confined, so we can reach tissues, bones, and organs with high spatial precision that haven’t been reachable with light-based printing methods.”

In the DVAP process, the biocompatible “sono-ink” is injected into the target area, and a specially designed ultrasound probe is used to harden it in place, creating intricate structures. The liquid nature of the ink allows for easy injection into targeted areas, and as the ultrasound printing probe moves, the ink’s materials link together and solidify. Any remaining unhardened ink can be removed using a syringe.

The researchers have successfully formulated different versions of the sono-ink, ranging from durable bone-like scaffolds to softer, more flexible heart valves. In experimental tests, the team sealed off a section inside a goat’s heart to prevent blood pooling, addressed a bone defect in a chicken leg, and demonstrated the controlled release of a chemotherapy drug inside a liver using a special sono-ink hydrogel.

While the technology shows immense promise, the researchers emphasize the need for further research before its clinical application in humans. Y. Shrike Zhang, coauthor and associate bioengineer at Harvard’s Brigham and Women’s Hospital, stated, “We’re still far from bringing this tool into the clinic, but these tests reaffirmed the potential of this technology. We’re very excited to see where it can go from here.”

By Impact Lab