Leslie Yeo, a research scientist at Monash University in Australia who’s research we profiled last year, is a finalist for the country’s 2008 People’s Choice award. Now don’t go looking for Yeo on the TV singing Besame Mucho, as the award is hosted by the Australian Museum which lets the public choose between six innovative researchers in different fields of science. Leslie Yeo is working on a device that uses the tea-leaf paradox to separate red blood cells from plasma with a bit of whirling.
From Leslie Yeo’s profile on the award’s website:
Using Leslie’s method, a tiny amount of blood is placed into a micro-chamber. The tip of a needle is placed at an angle, close to the surface of the blood. A voltage is applied to the needle generating ions around its tip in a way similar to lightning. These ions that repel the other oppositely changed charged ions close to it, causing an “ionic wind”. This “ionic wind” sweeps across the surface of the blood, causing the blood to swirl.
When the blood circulates, you would expect the blood cells and other microscopic particles to be pulled to the outside wall of the chamber due to centrifugal force. However, Leslie saw something different – the particles were pulled inwards near the bottom of the chamber, almost like a tornado. He found that the microscopic particles in the blood spiralled inwards toward the bottom of the chamber, leaving a clear layer of plasma above all in a matter of seconds.
This phenomenon, known as the “tea leaf paradox”, was first explained by Einstein in 1926 when he noticed that tea leaves collected at the centre of the bottom of a stirred teacup instead of being expelled outwards.
The tiny chamber of blood, like the tea cup, is a cylinder of liquid that is rotated at the top by the ionic wind while the base remains still. Einstein proposed that friction at the base of the cup retarded the usual centrifugal force in the liquid at the bottom of the cup, causing a downward swirling flow that pushed particles in instead of out.