A rocket engine transporting astronauts to space. A bridge-to-transplant device that keeps patients with failing hearts alive. By understanding complex fluid dynamics present in both scenarios, a team of NASA engineers working alongside physicians designed a next-generation machine — the continuous flow Left Ventricular Assist Device — to help those with end-stage heart failure.
That work, which began in the 1980s, has inspired the research taking place today inside UNLV’s Fluid Innovation Lab. The lab is led by mechanical and aerospace engineer Huang Chen, who is finding ways to leverage the complexity of fluid flow in turbomachines to solve biomedical engineering challenges that can fit in the palm of your hand.
“They stripped the design directly from the space shuttle main engine fuel pumps and scaled it down to put into people’s hearts,” said Chen. “So, that’s how I connected my research in fluid dynamics to this field.”
For Chen, both the space shuttle engine and the heart are “amazing machines.” His lab is merging technologies of the former with the latter to develop novel mechanical devices for blood circulation for adult and pediatric use.
“Our big goal is to improve the hemocompatibility of medical devices, improve patients’ health and better treat and eventually cure heart failures,” Chen said.
The Heart: An ‘Amazing Machine’
Chen leads a team of nine graduate and undergraduate students, who work out of a lab on the third floor of UNLV’s Advanced Engineering Building. With a focus on innovating mechanical devices that can replace the function of the heart, he’s been building his lab and his research portfolio since arriving at UNLV in fall 2023.
“The main function of the heart is to pump blood to the body,” he said. “Once heart disease progresses, the heart will eventually stop this function to pump blood.”
Chen’s collaborative research projects address two populations: The first is those with end-stage heart failure who rely on the LVAD as a bridge-to-transplant or destination therapy, and the second is patients who, as children, have undergone the Fontan procedure to address complex congenital heart defects where only one ventricle is functional.
Today, the heart transplant is still the gold standard of treatment for these patients. But transplants are limited by the number of available donors. According to the Organ Procurement and Transplantation Network, about 4,500 heart transplants occur annually in the U.S.
“My research is trying to design better devices — fluid mechanically — that are gentle on the blood and can support a patient for a long time, for 10, 20, or more years,” Chen said.
Blood, as Chen notes, is very different from fuel, the main component in rocket engines or waterjet pumps from which he derives his inspiration.
“If you want to use a pump to replace the function of the heart, the pump has to rotate pretty fast, at several thousands of RPMs,” Chen said. “That fast rotation generates a lot of turbulence, which can churn and damage the blood cells.”
The blood damage can cause abnormal bleeding and clotting, which leads to stroke and other adverse effects. About half of those who use the LVAD technology experience severe complications within two years, with only a handful surviving 10 years post implantation.
“It’s not a perfect technology,” Chen said. “My research wants to solve this problem from a fluid mechanics standpoint with innovations that help the blood flow more smoothly and prevent turbulence.”
Chen’s team is also exploring flexible blades made from polyurethane and slippery coatings for the intricate parts of the device.
They’re also addressing the complications that children born with only one working heart ventricle face. Without intervention, the condition is fatal.
To reestablish blood flow, patients usually undergo a three-stage surgical heart repair, the final being the Fontan procedure.
After the procedure, children still rely on a single left ventricle serving as the main pumping chamber, but the blood can now flow through the lungs and body. This unique physiology, however, usually leads to liver and lung issues, with the need for a heart transplant arising in early adulthood.
“We want to insert a secondary pump inside this unique circulation system so that it can function as the right heart in order to reestablish the two-pump system,” Chen said, adding that it would reduce complications and potentially be a long-term solution, eliminating the need for heart transplants among this population.
Lab Innovations to Clinical Solutions
The novel implantable device called “ReVolution” is being developed by Chen, a co-principal investigator, in collaboration with a team of experts from the Baylor College of Medicine, Texas Children’s Hospital, and the Texas Heart Institute. The pump in the ReVolution device also includes a rotor — designed by one of Chen’s collaborators — that is magnetically levitated by a drive system, greatly reducing the stress placed on the blood.
Chen’s contribution is to optimize the pump to reduce blood damage. He’s studying the effectiveness of the pump by simulating a circulatory system. He uses a blood analog — a mixture of water and glycerin — and injects tiny particles into the fluid as it moves through the system. A laser sheet illuminates the flow field, and a high-speed camera captures the particles on their journey, a technique called Particle Image Velocimetry (PIV). Chen’s team designed a computational framework to assess the effectiveness of the device.
The interdisciplinary nature of the ReVolution team — spanning both academia and healthcare — is reflective of the Fluid Innovation Lab’s goals to partner with clinical providers across Southern Nevada and the Southwest region to solve other fluid mechanics issues in the human body.
“The human person is 70% made of water,” Chen said. “So, naturally, there are a lot of fluid mechanics problems inside the human body. There’s complex flow dynamics in the heart and in other vessels like pulmonary arteries, which we may explore down the line.”
The key, he said, is to collaborate with the health care specialists who are working with these problems on a daily basis.
“It’s not just us in the lab scratching our heads saying ‘Hey, I think that problem is interesting so I’ll work on that,’” Chen said. “Our goal is to solve clinical problems.”