SMALL PRINTS:WHAT DO YOU DO when you are studying something small, and you want to know more about how it works? You make it bigger and slow it down of course. That's what researchers in Galway have been doing with a mechanical heart valve – their scaled-up model is six times the size and runs about 100 times more slowly than a mechanical valve which would be implanted into a human heart.
And using their bigger, slower version, they have been taking a closer look at the potentially damaging turbulence that can arise as blood flows through the prosthetic valve – with the aim of coming up with a better design.
Mechanical valves are used in about half of all heart valve replacements, explains researcher Dr Nathan Quinlan (pictured right) from the National Centre for Biomedical Engineering and Science (NCBES) at NUI Galway.
“Unlike tissue heart valves, are extremely durable,” he says. “But they make the patient prone to clotting, probably because of the disturbed blood-flow they create.”
Patients take medication to reduce the risks, but that can bring unwanted side-effects. “The challenge is to develop a valve which will avoid the thrombotic or clotting reaction,” says Quinlan.
So he and Dr Alessandro Bellofiore in the Biomechanics Research Centre in NCBES developed the model of the mechanical valve to help them better understand the finer details of how blood flows through it.
“Engineers love scale models,” says Quinlan, who lectures in mechanical and biomedical engineering at NUIG. “If youre developing an airliner, you make a small-scale model and study it in a wind tunnel, because the real thing is inconveniently large. We have the opposite problem – medical devices are small and they have effects on individual cells, so it’s important to understand how the flow of blood operates at very small scales. One way to get a better picture of those small scales is to make everything bigger.”
Their super-sized model contains Perspex, so they can to look at what is happening as fluid moves through it, and steel inserts to correct the mass of the valve and ensure that the dynamics scale properly, he explains. To see how it works in practice, the researchers added particles to fluid and used flashes of laser light to make them visible as they moved through the scaled-up model.
Then, by taking and analysing digital images of the particles, they could build up a map of how the fluid moves through the model, as well as calculating stress and estimating the damage that a blood cell accumulates as it is swept through the valve. Results from the heart valve model feature in the September issue of the Annals of Biomedical Engineering and the next step is a Science Foundation Ireland-funded project to look more closely at flow through the valve hinge, which is where most damage can occur, explains Quinlan.
“This will probably need a bigger model,” he says. “If we can understand the mechanisms that connect valve design to blood damage, we can design a better valve.”
Claire O’Connell
Tales from the Nanoworld
THERE IS SMALL and there is really small. Take a human hair at about a millionth of a meter in diameter and reduce this by 1,000 to the diameter of a typical molecule of DNA. This is the scale where scientists involved in nanotechnology operate. They measure objects in billionths of a metre across. It is this curious world that will be explored in a free public lecture to be given by Trinity College Dublin’s Prof Michael Coey next Tuesday.
Tales from the Nanoworld is the title for a talk about Coey’s research in the nanoworld where atoms can be counted and wires billionths of a metre across can be formed. Coey has spent decades searching for novel magnetic materials.
Coey is the inaugural recipient of the RDS/Intel Prize Lecture for Nanoscience. Supported by The Irish Times, the award recognises exceptional research in this important area of science and requires the recipient to give a public lecture where the research is described.
RDS Concert Hall, Tues 7pm, free but must book. Contact science@rds.ie or 01-2407289.
– Dick Ahlstrom