Notre Dame Researchers Can Now 3D Print Blood Capillary Networks

The Capillary Problem

Researchers at the University of Notre Dame have developed a hybrid bioprinting method that can fabricate vascular networks with capillaries smaller than 10 micrometers in diameter. The work, published in Nature Chemical Engineering, addresses the biggest bottleneck in 3D printed organs: plumbing at the scale of living tissue.

Scientists have been able to print centimeter-scale tissue scaffolds for years. They have also printed millimeter-scale blood vessels. But capillaries are different. These microscopic channels are where oxygen, nutrients, and waste actually move between blood and cells. Without them, printed tissues thicker than a few millimeters starve at the center.

Organ transplants come with their own problems: lifelong immunosuppression, strict lifestyles, and the constant risk of rejection. The dream is to print organs and tissues from a patient's own cells. That dream depends on solving the capillary problem.

Two Printers, One Scaffold

The Notre Dame approach uses two complementary techniques. First, extrusion printing lays down a soft, gel-like matrix that mimics human tissue. Then aerosol jet technology prints threads of gelatin on top. Those threads act as sacrificial channels, which are later removed to leave hollow vessels embedded inside the matrix.

The trick is that the researchers use machine learning to autonomously optimize print parameters for different vascular configurations. That means the system can adapt as the geometry gets more complex, without a human tuning every setting.

The team produced stable one-, two-, and three-dimensional vascular structures. Some channels were successfully lined with living cells. That is a long way from a printed kidney, but it is the kind of incremental result that matters.

Why This Could Matter

Lead author Yuxuan Liao and senior author Yanliang Zhang collaborated with Y. Shrike Zhang at Harvard Medical School and Brigham and Women's Hospital. The long-term goal is an intelligent, autonomous bioprinter capable of fabricating functional tissues and organs, including the liver, kidneys, and heart.

That is still years away. In the near term, the method could improve drug testing, disease modeling, and wound healing patches. Any application that needs living tissue with a blood supply could benefit from a reliable way to build capillary networks.

The field has seen plenty of dramatic organ-printing announcements. This one is more modest, and that is exactly why it is worth watching. It targets the unglamorous middle layer, the microvascular network, without which organ printing stays a lab demonstration.