CU Boulder engineers show how oxygen can enable multi-hardness 3D printing for biomedical uses


A team of engineers from the University of Colorado Boulder recently published a study detailing a new 3D printing technique for biomedical applications. The innovative process makes it possible to 3D print objects with varying (and controlled) degrees of firmness. It could one day be useful for printing artificial arteries and human tissues for better treating hypertension or other vascular diseases.

The process itself, detailed in the journal Nature Communications, consists of a bio-stereolithography printing technique that utilizes the presence of oxygen to program and control a given part’s rigidity. For biomedical applications, the research team says this ability could make it possible to recreate complex blood vessel networks, as they are structured but also pliable.

“The idea was to add independent mechanical properties to 3D structures that can mimic the body’s natural tissue,” commented Xiaobo Yin, an associate professor in CU Boulder’s Department of Mechanical Engineering and the senior author of the study. “This technology allows us to create microstructures that can be customized for disease models.”

Typically, hardened blood vessels are a symptom of cardiovascular disease, and it has remained challenging within the medical sphere to find a treatment and replacement for diseased blood vessels. Using 3D printing as a potential solution is showing some promise as researchers from around the globe are working towards a shared goal using various AM processes.

CU Boulder oxygen 3D

In this particular case, the University of Boulder engineers have leveraged the presence of oxygen in the printing process to “set” a 3D printed structure with varying hardnesses. “Oxygen is usually a bad thing in that it causes incomplete curing,” explained Yonghui Ding, a postdoctoral researcher in Mechanical Engineering and the lead author of the study. “Here, we utilize a layer that allows a fixed rate of oxygen permeation.”

In other words, the team has found a way to precisely control the oxygen migration and resulting light exposure to create different hardnesses within a single part. “This is a profound development and an encouraging first step toward our goal of creating structures that function like a healthy cell should function,” Ding added.

To showcase how the method works, the team 3D printed multiple version of a single design consisting of a top beam supported by two rods. Using the same 3D model, the same scale and materials, the researchers successfully 3D printed three variations in rod fragility: soft/soft, hard/soft and hard/hard. In another example, the research team 3D printed a Chinese warrior figure so that it had a hard exterior and a soft interior.

At this stage, the 3D printer used by the team is capable of printing with biomaterials at a minimum scale of about 10 microns. Moving ahead, the engineers say they hope to further advance the process by refining the scale and explore more biomedical applications.

CU Boulder engineers show how oxygen can enable multi-hardness 3D printing for biomedical uses