Biocompatible ink absorbs soundwaves to harden 3D-printed shapes

This development is particularly significant for its potential applications in biomedical fields such as bone healing and heart valve repair, as it can be used in deeper tissues.

Unlike many traditional 3D-printing methods, which often involve slow, point-by-point object construction, this new method leverages a fully inorganic stamp to create uniform 2D material stacks.

Explaining the innovation, Yao said: “DVAP relies on the sono-thermal effect, which occurs when soundwaves are absorbed and increase the temperature to harden our ink. 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.”

The process begins with a sonicated ink, known as sono-ink, a blend of hydrogels, microparticles, and molecules designed to react specifically to ultrasound waves. Once injected into the target area, a specialised ultrasound printing probe sends focused ultrasound waves into the ink, transforming it into complex structures, ranging from bone-like scaffolds to hydrogel bubbles that can be placed on organs.

“The ink itself is a viscous liquid, so it can be injected into a targeted area fairly easily, and as you move the ultrasound printing probe around, the materials in the ink will link together and harden,” explained Zhang. “Once it’s done, you can remove any remaining ink that isn’t solidified via a syringe.”

The versatility of the sono-ink allows the team to tailor the formula for various uses, such as adding bone mineral particles for bone healing or adjusting the durability and degradability of the final product. The team has already demonstrated the efficacy of this technique in several proof-of-concept tests.

One such test involved sealing off a section in a goat’s heart to mimic treatment for nonvalvular atrial fibrillation. The sono-ink was delivered via a catheter to the goat heart's left atrial appendage, and the ultrasound probe hardened the ink through 12mm of tissue without harming the surrounding organ.

In another test, they addressed tissue reconstruction and regeneration using a chicken leg bone defect model. The sono-ink was injected and solidified through layers of skin and muscle tissue, bonding seamlessly to the bone without impacting surrounding tissues.

Lastly, the potential of DVAP for therapeutic drug delivery was explored by incorporating a chemotherapy drug into the ink, which was then delivered to sample liver tissue. The resultant hydrogels slowly released the chemotherapy into the liver tissue.

“We’re still far from bringing this tool into the clinic, but these tests reaffirmed the potential of this technology,” Zhang stated. “We’re very excited to see where it can go from here.”

Yao highlighted the broad potential of this innovation, saying: “Because we can print through tissue, it allows for a lot of potential applications in surgery and therapy that traditionally involve very invasive and disruptive methods. This work opens up an exciting new avenue in the 3D printing world, and we’re excited to explore the potential of this tool together.”