19th century photography technique used in a new method of data storage

Clark Johnson says he wanted to become a scientist from the age of three. At the age of 8, he got bored with a telegraph kit he received as a gift, and he converted it into a telephone. By age 12, he decided to study physics because he wanted to understand how things work at the most basic level.

“At the time, I mistakenly believed that physicists were tuned to the left ear of God,” Johnson says.

After graduating in 1950 at the age of 19 from the University of Minnesota Twin Cities with a bachelor's degree in physics, he was about to enroll in graduate school when he received a call from the head of the physics department at a 3M research laboratory offering him a job. Tempted by the prospect of making things with his own hands, Johnson accepted a position as a physicist at the company's St. Paul, Minnesota facility. Thus began his more than seventy-year career as an electrical engineer, inventor, and entrepreneur that continues to this day.

Johnson, an IEEE Life Member, is an active member of the IEEE Magnetics Society and served as its president in 1983-1984.

He served on the House Science Committee before being hired by the Advanced Research Projects Agency (ARPA) and assigned to MIT's communications policy research program, where he contributed to the development of HDTV.

He later helped found the company Wave Domain in Monson, Massachusetts. Johnson and his Wave Domain cohorts have received six patents for their latest invention, the standing wave storage system (SWS), which enables low-power, tamper-resistant archival data storage using legacy photographic technology.

3M, HDTV and a career full of color

3M proved to be fertile ground for Johnson's creativity.

“You could spend 15% of your time working on something you liked,” he says. “The president of the company believed that new ideas appeared out of thin air, and if you poke around, you might stumble upon something useful.”

As a result of these thoughts, Johnson became involved in the development of the audio cassette cartridge and Scotchlite, a reflective film that can be seen on roads, signs and more.

In 1989, he was offered an IEEE Congressional Fellowship. He chose to work with Representative George Brown Jr., a Democrat who represented the 42nd District in central California. Brown was a member of the House Science, Space and Technology Committee, which oversees nearly all non-defense and health-related research.

“It was probably the most exciting year of my life,” Johnson says.

While serving on the science committee, he met Richard Jay Solomon, who was assistant director of MIT's communications policy research program and testified before the committee on video and telecommunications issues. Solomon's biography is very diverse. In the early 1960s, he studied physics and electrical engineering at Brooklyn Polytechnic Institute and general science at New York University. Before becoming a research fellow at MIT in 1969, he held various positions. He ran a scientific photography magazine and founded a company that provided consulting on urban planning and transportation issues. He has authored four textbooks on transportation planning, three of which were published by the American Society of Civil Engineers. While working for the magazine, Solomon gained insight into abstruse, long-forgotten 19th-century photographic processes that would prove useful in future inventions.

Johnson and Solomon bonded over their shared interest in trains. At the time they met, Johnson owned a railroad car that was stationed at Union Station in the District of Columbia, and he used it to travel around North America, traveling approximately 1,300,000 km before selling the car in 2019. Johnson and Solomon made many trips together aboard the refurbished Pullman.

They are now collaborating to develop a new method for storing big data on tamper-proof media with zero energy consumption.

Traditional storage devices such as solid-state drives and hard drives require energy to maintain and can deteriorate over time, but Johnson says the technology he, Solomon and his co-authors developed requires virtually no energy and can last for centuries under almost any conditions. conditions.

Long before working on their latest project, Johnson and Solomon joined forces in another high-profile endeavor: the development of high-definition television. This project arose from their work on the Congressional Science Committee.

In the late 1980s, engineers in Japan were working to create an analogue high-definition television system.

My boss on the science committee said, “We can't let the Japanese do this. There are all these digital technologies and digital computers. We have to do it digitally,” says Johnson.

This led to a joint project funded by NASA and ARPA (the predecessor to modern DARPA). After Johnson's tenure on the scientific committee ended, he and Solomon joined the MIT team involved in the collaboration. While developing what became the dominant television technology, Johnson and Solomon became experts in optics. Working with Polaroid, IBM and Philips in 1992, the team demonstrated the world's first progressive scan high-definition digital camera at the annual conference of the National Association of Broadcasters.

Accidental discovery

Around 2000, Clark and Solomon, along with new colleague Eric Rosenthal, began working as independent consultants for NASA and the US Department of Defense. Prior to teaming up with Clark and Solomon, Rosenthal was vice president of research and development at Walt Disney Imagineering and general manager of audiovisual systems development at ABC Television.

While working on a DARPA-funded project, Solomon came across a page in a century-old optics textbook that caught his attention. It described a method developed by the famous physicist Gabriel Lippmann for obtaining color photographs. Instead of using film or dyes, Lippmann created photographs using a glass plate coated with a specially formulated silver halide emulsion.

When illuminated by bright sunlight, the entire spectrum of light was reflected from the mercury-based mirror coating on the back of the glass. It created standing waves inside the emulsion layer that retained the corresponding colors (wavelength). The grains of silver in the brightest parts of the standing wave oxidized, as if remembering the exact colors they saw. (This was in stark contrast to traditional color photography and television, which preserve only the red, green and blue portions of the spectrum.) Chemical treatment then turned the oxidized silver halide grains black, leaving the light waves imprinted on the medium in a way that was virtually impossible to alter. For his work, Lippmann received the Nobel Prize in Physics in 1908.

Lippmann's photographic technique was not a commercial success because there was no practical way to duplicate images or print them. In addition, at that time, emulsions required very bright light to print properly in the medium.

Still, Solomon was impressed by the longevity of the resulting image. He shared the process with his colleagues, who realized the possibility of using this technique to store information for archival purposes. Johnson saw old photos Lippmann at the Museum of Photography in Lausanne (Switzerland), where he noticed that the colors were clear and saturated, despite being more than a century old.

Solomon liked the silver halide method, and in 2013 he and Johnson returned to Lippmann's emulsion photography technique.

“We started talking about how we could take all this information we knew about color and use it for something,” Johnson says.

Data in space and on Earth

In 2013, when Rosenthal was visiting the International Space Station headquarters in Montgomery, AL, one of the top scientists said, “The data stored on the station is being erased by cosmic rays every 24 hours,” Rosenthal recalled. “And we have to rewrite the data over and over again.” Cosmic rays and solar flares can damage electronic components, causing errors or complete erasure of data on hard drives and other traditional storage systems.

Rosenthal, Johnson and Solomon knew that properly processed silver halide photographs were not susceptible to such hazards, including electromagnetic pulses from nuclear explosions. The team re-examined Lippmann's photographic emulsion.

Solomon's son, Brian Solomon, a professional photographer and emulsion maker, was also concerned about the durability of conventional dye-based color photographs, which typically begin to fade after a few decades.

The team came up with an intriguing idea: Given how long-lasting Lippmann's photographs have proven to be, what if they could use a similar technique—not to create analog images, but to store digital data? Thus began their new engineering endeavor: changing the way they store archived data—data that doesn't need to be overwritten, but simply stored and read from time to time.

According to Johnson, ordinary data is sometimes protected by making multiple copies or constantly rewriting it. However, these methods require energy and can be labor intensive.

The amount of data that needs to be stored on earth is also growing by leaps and bounds. According to Data Bridge Market Research, the market for data centers and other artificial intelligence infrastructure is growing at 44% per year. Commonly used hard drives and solid state drives consume some amount of power even when not in use. Standby power consumption ranges from 0.05 to 2.5 watts per drive. And data centers contain huge numbers of disks, requiring huge amounts of electricity to keep them running.

Johnson estimates that about 25% of the data stored in modern data centers is archival in nature, meaning it does not need to be rewritten.

“Write once, read forever” technology

The technology developed by Johnson, Solomon and their colleagues promises to overcome the power requirements and vulnerabilities of traditional storage systems for archival applications.

The development is based on Lippmann's idea. Instead of taking analogue photography, the team divided the medium into pixels. With the help of emulsion specialist Yves Jeantet, they refined the chemistry of Lippmann's emulsion, making it more sensitive and capable of storing multiple wavelengths in each pixel. The final emulsion is a combination of silver halide and hardened gelatin. Each pixel can now store up to four different narrowband, overlaid colors.

“The textbooks say it’s impossible,” says Solomon, “but we did it, so the textbooks are wrong.”

For each pixel, you can select four colors out of 32 possible to store.
This amounts to over 40,000 options. Thus, the technique can store more than 40,000 bits (although the format does not have to be binary) in each 10-square-micrometer pixel, or 4.6 terabits in a modified 10.16 cm by 12.7 cm Lippmann wafer. That's more than 300 movies stored in one picture.

To write to SWS media, a platter coated with a thin layer of a specially formulated emulsion is exposed to light from an array of high-power color LEDs.

This way, the entire platter is written at the same time, significantly reducing the write time per pixel.

The plate then goes through a chemical development process that blackens grains of silver that remember the color waves it was exposed to.

Finally, a small camera array with a charged pair, similar to those used in mobile phones, reads the information. Reading occurs from the entire platter at once, so the read speed, like the write speed, is very fast.

“The data we read comes from platters with enormous bandwidth,” says Solomon. “There's not a computer on the planet that can take them in without some kind of buffering.”

The entire memory cell is a sandwich of an LED matrix, a photosensitive plate and a CCD matrix. Ready-made parts are used for all elements.

“We spent a lot of time thinking about how to do this in a very inexpensive, repeatable and fast way,” says Johnson. “The idea is to use parts that are readily available.” The entire storage medium, along with the read/write infrastructure, is relatively inexpensive and portable.

To test the longevity of their data storage method, the team sent about 150 samples of their SWS devices to their NASA colleagues, which astronauts suspended outside the International Space Station for nine months in 2019. They then verified the integrity of the stored data after the SWS wafers returned from space by comparing them with the other 150 wafers stored in Rosenthal's laboratory on the ground.

“Nine months of exposure to cosmic rays had absolutely no effect on their preservation,” says Solomon. At the same time, the plates on Rosenthal’s table were infested with bacteria, while the plates on the ISS were sterile. However, silver is a known bactericide, so the paints were immune, Solomon says.

Their latest patent, issued earlier this year, describes a data storage method that requires no power to maintain when there is no active reading or writing of data. Team members claim that this method is impervious to change: It is impervious to moisture, solar flares, cosmic rays and other types of radiation. Therefore, in their opinion, it can be used both in space and on earth as a durable and inexpensive solution for storing archival data.

Passing the baton

The new invention has a huge number of potential applications. In addition to data centers and space applications, scientific facilities such as the Rubin Observatory under construction in Chile will produce enormous amounts of archived data that can be exploited by SWS technology, Johnson said.

“This is all reference data, and every week there is a huge amount of data generated that needs to be stored forever,” Johnson says.

However, Johnson says he and his team won't have time to bring the technology to market: “I'm 94 years old, and my two partners are in their 70s and 80s. We're not looking to build a startup.”

He's ready to pass the baton. The team is looking for a new leader to lead Wave Domain, which they hope will continue the development of SWS and bring it to mass adoption.

Johnson said he realized that people rarely know which new technologies will ultimately have the biggest impact. Perhaps, although few people know about it now, storing big data using old photographic technology will be an unexpected success.