We’ve seen plenty of 3D printed heart models used as helpful surgical planning tools, and 3D printing technology has helped with heart conditions in many other ways, like 3D printed patches that can help treat ischemia, using artificial intelligence to analyze 3D virtual hearts, and special 3D printed medical tools surgeons use during complicated surgeries. But what we haven’t seen is a 3D printed artificial heart, made of silicone, that has a heartbeat – and that’s just what researchers from the Functional Materials Laboratory at ETH Zurich have developed.

It’s the first entirely soft artificial heart ever created. Silicone has been used in medical 3D printing before, making better breast implants and creating lifelike prosthetics, but the silicone heart created by ETH Zurich is something new. The researchers, together with colleagues from the Product Development Group Zurich, which is led by Professor Mirko Meboldt, have been testing the soft 3D printed heart to determine how well it can function in comparison to a real heart.

[Image: Zurich Heart]

Wendelin Stark, Professor of Functional Materials Engineering at ETH Zurich, is leading the project. The mold for the heart was created using Siemens CAD software, and a 3D printing, lost-wax casting technique was used to create the silicone heart, which weighs nearly 400 grams; a Stratasys uPrint SE Plus and an HP Designjet 3D were used for the actual 3D printing. It looks like a real heart, and features both a left and right ventricle; however, the ventricles are separated by another chamber and not a septum.

Doctoral student Nicholas Cohrs said, “It is a silicone monoblock with complex inner structure.”

Pressurized air is used to inflate and deflate the artificial heart, which is necessary to pump fluid from the blood chambers – this action replaces the muscle contraction of a real human heart. This is the aim of the project – to mimic a real human heart as much as possible. Conventionally manufactured blood pumps can cause problems, as the mechanical parts can suffer from complications while the patient is left without a physiological pulse.

Cohrs explained, “Therefore, our goal is to develop an artificial heart that is roughly the same size as the patient’s own one and which imitates the human heart as closely as possible in form and function.”

The research team published the results of their experiment, which evaluated how the artificial 3D printed heart performed, in a paper, titled “A Soft Total Artificial Heart – First Concept Evaluation on a Hybrid Mock Circulation,” in the Artificial Organs scientific journal; co-authors include Cohrs, Meboldt, and Stark, along with Marianne Schmid Daners, Volkmar Falk, A. Xavier Kohll, Michael Loepfe, Anastasios Petrou, Christoph M. Schumacher, Christoph T. Starck, and Maria Yliruka.

The paper’s abstract explains, “The technology of 3D-printing has allowed the production of entirely soft pumps with complex chamber geometries. We used this technique to develop a completely soft pneumatically driven total artificial heart from silicone elastomers and evaluated its performance on a hybrid mock circulation. The goal of this study is to present an innovative concept of a soft total artificial heart (sTAH). Using the form of a human heart, we designed a sTAH, which consists of only two ventricles and produced it using a 3D-printing, lost-wax casting technique. The diastolic properties of the sTAH were defined and the performance of the sTAH was evaluated on a hybrid mock circulation under various physiological conditions. The sTAH achieved a blood flow of 2.2 L/min against a systemic vascular resistance of 1.11 mm Hg s/mL (afterload), when operated at 80 bpm. At the same time, the mean pulmonary venous pressure (preload) was fixed at 10 mm Hg. Furthermore, an aortic pulse pressure of 35 mm Hg was measured, with a mean aortic pressure of 48 mm Hg. The sTAH generated physiologically shaped signals of blood flow and pressures by mimicking the movement of a real heart. The preliminary results of this study show a promising potential of the soft pumps in heart replacements. Further work, focused on increasing blood flow and in turn aortic pressure is required.”

Figure S1. Sketch of the soft total artificial heart with outer dimensions in millimeters. c) depicts the flow direction to and from the right ventricle (RV) and left ventricle (LV).

The team was able to prove that the 3D printed artificial heart works and moves just like a real heart does. However, at the moment, the soft heart only lasts for roughly 3,000 beats, which equals less than an hour, before the material can’t stand the strain of beating any longer. But this doesn’t seem to bother the researchers.

“This was simply a feasibility test,” explained Cohrs. “Our goal was not to present a heart ready for implantation, but to think about a new direction for the development of artificial hearts.”

The 3D printed silicone heart research is actually a sub-project of the University Medicine Zurich Heart Project, which brings together 20 research groups from multiple institutions and disciplines in Berlin and Zurich. Part of the research, while displaying how 3D printing technology can yet again improve the medical field, also focuses on improving blood pumps. This is vitally important, as about 26 million people around the world suffer from heart failure, and there aren’t nearly enough donor hearts available; good artificial blood pumps can really help a patient hang on until they receive a new heart.

Doctoral students from the Product Development Group Zurich developed a testing environment that will allow them to simulate the cardiovascular system, and the ETH Zurich team working on the silicone heart used the environment for their work, which, in addition to 3D printing technology, also included using a fluid that has comparable viscosity to human blood.

Petrou said, “Currently, our system is probably one of the best in the world.”

However, before the soft heart is ready for use in the open market, its performance and tensile strength will need to increase so it can last longer. But the team isn’t ready to stop working on the heart just yet.

“As a mechanical engineer, I would never have thought that I would ever hold a soft heart in my hands,” said Petrou. “I’m now so fascinated by this research that I would very much like to continue working on the development of artificial hearts.”

Discuss in the Silicone Heart forum at 3DPB.com.

[Source: ETH Zurich]

 

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