Seeking to improve how surgeons train for complex procedures, a team of engineers from Carnegie Mellon University has recently developed a new method for 3D printing realistic models of the human heart.

While 3D printing organs isn’t a new development, current models lack the texture of the real thing because the materials they’re made of are either too stiff or too soft. This makes the models unsuitable for doctors to practice the actual surgery on them. This is where the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) technique comes in.

The novel method uses a “bio-ink” made up of a natural polymer known as alginate. During the printing process, the bio-ink is injected into a hydrogel bath which helps hold the delicate organ model in place. Once the printing is complete, the researchers apply heat to the model, melting the hydrogel away. What’s left behind is a heart replica that mimics the elasticity of a real human heart, and can be cut and sutured in a similar manner.

“We can now build a model that not only allows for visual planning but allows for the physical practice,” says the study’s lead author Adam Feinberg. “The surgeon can manipulate it and have it actually respond like real tissue so that when they get into the operating site they’ve got an additional layer of realistic practice in that setting.”