Lycurgus Cup: Ancient Roman Nanotechnology Aiding the Worlds of Tomorrow

 

 

Lycurgus Cup 4th Century CE
Images Courtesy of the British Museum

The Lycurgus Cup is a Roman glass cage cup, or diatretum, made of dichroic glass. This means that the properties of the glass allow it to change color depending from which angle light is shown through. If lit from behind the glass turns red and green if lit from the front.  The cup depicts the ancient Greek myth of the Thracian King Lycurgus. Lycurgus was fated a horrible death by Dionysus who cursed him for banning his religion and imprisoning his followers. There are several variation of this myth, but the reference seen on the cup ( Lycurgus trapped in wine vines) is not common variation. However, there is a satyr and a figure believed to be Dionysus (due to panther [Dionysus' patron animal] and the thyrsus [a staff with a pine cone tip carried by his followers]) who are expressing angry gestures.

The Lycurgus Cup is a rare item from history, whose use is still unknown and highly speculated. It has been thought to have been used in the rites of Bacchus (Dionysus Roman counterpart). However, this can not be proved. Coincidentally, the Historia Augusta records the gift of two dichroic cups from Emperor Hadrian to his brother-in-law Servianus via a letter. Perhaps, this may have been one of them.

The British Museum acquired the cup in 1950's, but it wasn't until the 1990's that they understood its properties. Researchers analyzed broken fragments of the cup until they discovered that the Romans were nanotechnology pioneers. The glass effect of the Lycurgus Cups was achieved by making the glass with minutely ground gold and silver dust. The size of these particles of silver and gold are only about 50 nanometers across (less than one-thousandth the size of a grain of table salt) and required a transmission electron microscope to be seen. Thus, it is highly impossible that Roman artists made these minute silver-gold alloy dust particles for this size of cup; therefore, these particles must have been added in large quantities to even large amounts of glass-melts. Thus, there may have been other dichroic glass items made from the same glass-melt as the Lycurgus Cup.

The color changing ability of the glass is due the size of metal flecks and how their electrons vibrate that alters the color. Gang Logan Liu, an engineer at the University of Illinois, conjectured that when various liquids filled the cup it would change the vibration of the electron and thus the color. Thus, he argued that the Lycurgus Cup's phenomenon was very similar to a home pregnancy test, which uses a nano-based technology to turn a white line pink at the presence of HCG in urine. So, researchers began to formulate an experiment to test this hypothesis.

Due to the fact that the Lycurgus Cup is a prized and unique artifact, researcher were unable to fill the cup itself. However, they created billions of wells (about the size of postage stamp) and sprayed them with a gold and silver nanoparticles. Thus, they created essential tiny version of the Lycurgus Cup. Then, they continued with experiment by filling these wells with different types of liquids. The result was as predicted and the colors ranged from light green for water to red for oil. This "well" prototype was 100 times more sensitive to the differing salt levels of tested liquids than current sensor used for similar testing.

Liu was hopefully to see if the Roman's nanotechnology of gold-silver alloy particles could have current science applications. This experiment proved that one day this technology may make its way to handheld devices for detecting pathogens in salvia or urine.