Scientists in Australia and China have discovered a method for permanently storing data in glass. Since it can hold information for thousands of years without needing an electrical supply, it is being highlighted as a storage medium that could replace hard disks and tapes used in major archives.
Researchers from the University of Sydney in Australia and Tsinghua University and Kunming University in China announced on the 26th that they had developed photochromic glass that can store information indefinitely in bulk by utilizing the principle of color change in response to light of specific wavelengths. This research was published in the international journal ACS Energy Letters, which is issued by the American Chemical Society (ACS).
As the artificial intelligence (AI) and big data industries grow, corporations are acquiring more data storage space. Government and public institutions are also demanding more storage space while managing public infrastructure through the Internet of Things (IoT). In the midst of rising electricity demands due to an increase in data centers, scientists are exploring data storage methods that produce fewer carbon emissions, which are a cause of the climate crisis. They have identified glass that can retain information for over 1,000 years without electricity as the most promising next-generation information storage medium.
Photochromic glass, which darkens in sunlight and remains transparent indoors, is among those materials. This glass, known as "photochromic," changes color only at specific wavelengths.
The research team reported that photochromic glass is a cheap and stable material and that they are developing technology for storing large amounts of information. To use glass as a storage medium, technology must be developed to compact a large amount of information in a small area and to write and erase it repeatedly, similar to hard drives or memory. The team has made progress on this goal by successfully drawing various patterns on gallium and silicate glass and modifying and erasing them.
The researchers injected magnesium and terbium ions into the glass using a process called "directly doped 3D lithography." The glass with injected ions changes color when exposed to light of specific wavelengths. The team etched various three-dimensional patterns, such as dots, QR codes, prisms, and birds on the glass substrate using a laser with a wavelength of 532 nanometers (nm; 1 nm is 1 billionth of a meter). These three-dimensional patterns serve as physical units for storing data. While these patterns appear purple on transparent glass, they change color when illuminated with light of specific wavelengths. For example, when a strong purple laser (wavelength 376 nm) is shone on the glass, terbium emits green light. When magnesium is subjected to a purple laser (wavelength 417 nm), it emits red light.
Although the research team is still in the early stages, they have also developed technology for erasing information stored in photochromic glass media. They confirmed that heating the glass for 25 minutes at 550 degrees allows them to erase patterns without altering the glass's structure.
The research team emphasized that this study is groundbreaking because magnesium and terbium operate at completely different wavelengths. This enables an increase in the amount of information stored in the glass's three-dimensional patterns. The researchers expect this technology to be widely used in high-capacity optical memory and encryption fields across industrial, academic, and defense sectors.
The industry is also showing interest in utilizing glass as the next-generation storage medium. Microsoft initiated Project Silica in 2016 to develop technology for storing large volumes of data on glass plates the size of coasters. This technology, first disclosed by the company in 2013, uses powerful lasers to create five-dimensional (5D) nanoscale structures to store information.
Glass storage media have a storage density 10,000 times higher than Blu-ray discs. Microsoft explained that it stores 7 terabytes (TB) of information on a glass substrate that is about the size of a DVD and 2 mm thick. Considering that a dual-layer DVD can hold up to 17 gigabytes (GB) of information, this represents a difference of about 400 times. In musical terms, it could hold 1.75 million songs, enough to play continuously for 13 years.
As of now, the company showing the most interest in utilizing glass storage media is Warner Bros. Microsoft collaborated with Warner Bros. to store the video file of the movie "Superman," released in 1978, on a small glass substrate. Warner Bros. is considering creating a permanent physical asset to store important digital content and provide durable backup copies of films.
Glass is inexpensive and is hardly influenced by temperature, humidity, fine dust, or electromagnetic fields. However, the slow speed of writing and erasing makes it seem difficult to use it in real-time for videos or music files. A physical storage unit called a voxel (the three-dimensional unit of a pixel) is used in glass storage devices. The fastest speed developed so far is 1 million voxels per second, which is equivalent to storing about 230 kilobytes (kB) per second in traditional data terms. Compared to SSDs (solid-state drives) found in laptops, which operate at 3,500 megabytes (MB) per second, this speed is significantly slower.
Experts believe that due to the physical properties of glass, it is more suitable for long-term storage devices used in archives rather than fast storage devices. Magnetic storage technologies, such as hard disks and tapes, which occupy the mainstream of the storage media market, have many limitations in terms of durability. The storage duration for hard disks is only 5 years and for tapes is 10 years, while glass can last for thousands of years.
China has consistently invested in optical information storage technology, including glass storage technology. This research has also attracted attention due to the full support received from the central and local governments in China. Funding has come from the National Natural Science Foundation of China, the Southwest joint graduate school science and technology project of Yunnan Province, key projects of the National Natural Science Foundation of China and Yunnan Provincial co-funding, the high-level foreign expert introduction plan of the National Natural Science Foundation of China, and the academic workstation for experts like Tatiana Cherkasova in Yunnan Province.
References
ACS Energy Letters(2025), DOI: https://pubs.acs.org/doi/abs/10.1021/acsenergylett.5c00024