The past few decades in technology advancement have increased data storage capacities while simultaneously reducing the size of storage devices. Yet until now, modern storage devices have not been designed with data longevity in mind. Researchers in the Netherlands recently tackled this underdeveloped facet of technology by developing a medium that can store data for one million years.
In 1956, a storage device had a capacity of 3.75 MB on 50 magnetic disks that were 24 inches in diameter. Today, consumers can purchase a 4TB hard drive stored on a 3.5-inch disk. Both disks, however, can retain data for only a decade.
The project to develop a long-lasting storage device was conducted at the University of Twente in the Netherlands and was published on Oct. 9th. Graduate student and lead researcher on the project, Jeroen de Vries, said that electrical engineering professor Miko C. Elwenspoek’s work inspired the project.
“[Elwenspoek] was involved with the human document project since the start of the project. This project involves a study to store information about the human race for well after the human race is gone,” de Vries said. “Since my PhD project involved magnetic data storage, this became a part of the research.”
De Vries explained that the medium required a high energy barrier to prevent erasing of data.
“Magnetic data storage is stored in the direction of the magnetization. In current hard disk systems, this is either up or down,” de Vries said. “It is possible that there are intermediate states which will in effect lower the energy barrier because it does not have to be overcome in one step.”
The storage medium embedded tungsten, which produced readable data, in silicon nitride. The silicon nitride was selected because it is transparent to light, has high fracture toughness and has a low tendency to expand at higher temperatures. Tungsten was selected for its low thermal expansion coefficient, high melting temperature and relatively low reactivity.
The tungsten produced Quick Response (QR) codes similar to barcodes that are easily decoded with modern smart phones. The first few samples of QR code were a centimeter wide and each pixel of code consisted of smaller QR codes that were a few micrometers in size. The codes were readable with an optical microscope. To increase data density, the QR codes were made small enough to be read by an electron microscope.
To test whether the data could be retained for one million years, the QR samples were exposed to a temperature of 473 Kelvin (200° C) for one hour.
“The idea behind the elevated temperature is to accelerate the aging process which can occur,” de Vries said. “We used a simple theory based on the Arrhenius law to determine the relevant temperature.”
One shortcoming of the Arrhenius law is that different chemical processes can occur at higher temperatures than at the lower temperature environment that the technology would experience. For example, temperatures similar to those found in a burning house extensively damaged the tungsten QR code lines. Another disadvantage is that prolonged exposure to oxygen can promote the diffusion of oxygen through cracks and react with tungsten to produce whisker-like structures, harming QR code readability.
Higher temperatures cracked the silicon-nitride top layer and reduced the number of readable QR codes, but the data was still readable. De Vries said that while cracks and whisker-like structures can cause data read-out failure, the QR can still be deciphered by additional effort.
“The tungsten is still present so the QR code could still be decoded with a little more effort,” de Vries said “The earth will change quite a lot in a million years so we need a very stable location.”
Despite facing unpredictable and limiting environmental changes, the million-year capacity of data storage in the innovative disk holds the promise of preserving the human race long after we have disappeared.
A version of this article appeared on page 5 of the Tuesday, November 24, 2013 print edition of the Daily Nexus.