Fluorescent dyes could play a central role in the quest for optical methods to ensure reliable and cost-effective data storage. A Harvard University research team has devised a way to store digital data in fluorescent dye molecules, using combinations of seven commercially available fluorescent dyes. The storage and read-out technique is fast, resistant to corruption, low-cost, and energy-efficient. First, the researchers “write” the information by inkjet-printing fluorescent dye solutions onto a reactive polymeric substrate that contains free amino groups. When the dyes are printed, a stable amide bond forms between the dye and the substrate, locking the dye onto the substrate at a specific location. The dyes are optimized to reduce photobleaching. The system “reads” information via fluorescence microscopy — specifically, a microscope, equipped with a multichannel fluorescence detector, that can simultaneously and independently resolve any combination of the dyes on the substrate. The inkjet printer enables writing of information at a rate of 16 bytes/s, and the multichannel fluorescence detector in the confocal microscope enables information to be read at a rate of 58 kilobytes/s. The fluorescence microscope detects the difference in wavelengths emitted by each dye molecule, distinguishing individual dyes in the mixture and detecting the presence or absence of specific dye molecules. Each number, letter, and pixel to be stored is represented by a group of zeros and ones, dependent on which dye molecules are present. In the current work, the researchers used the American Standard Code for Information Interchange (ASCII) to translate the information in the different dyes. The ASCII information is converted to a binary bit string, which is then encoded into printable patterns and printed with the inkjet printer. The use of molecule mixtures, instead of sequence-defined macromolecules, minimizes the time and difficulty of synthesis and eliminates the need for sequencing. An important characteristic of the new information storage method is that registration of the individual molecules is not required, the researchers said. To the best of the team’s knowledge, this characteristic is not found in any other optical data storage technologies. A data-storage system that uses fluorescent dyes has helped a team from Harvard achieve information storage with high density, fast read/write speeds, and multiple reads of a single set of molecules without loss of information, all at an acceptable cost. Courtesy of Kris Snibbe/Harvard staff photographer. The researchers stored a paper and image of Michael Faraday, the 19th-century English physicist and chemist, to demonstrate the new method. Using the new optochemical data storage approach, the team has written 14,075 bytes of digital information on a 7.2- × 7.2-mm surface, resulting in an aerial information density of 271.5 bytes/mm2. This information has been read over 1000 times without significant loss in fluorescent signal intensity. With the approach, the team achieved information storage with high density, fast read/write speeds, and multiple reads of a single set of molecules without loss of information, all at an acceptable cost, the team said. Theoretically, the data can be saved for a very long time; the long timeline of molecular data storage options is superior to that of current media devices for data storage, which can store information for 40 years at most. Traditional methods of data storage such as flash drives, Blu-rays, magnetic memory strips, and computer drives have strict size limits, are susceptible to water damage and hacking, and consume a lot of energy. Even the cloud has a storage limit — plus, the cloud requires large, expensive physical servers and is susceptible to being breached. “This method could provide access to archival data storage at a low cost,” researcher Amit Nagarkar said. “[It] provides access to long-term data storage using existing commercial technologies — inkjet printing and fluorescence microscopy.” The team’s optochemical data storage method could be used to store regulated information, such as financial and legal records, and for long-term storage. The fluorescent dyes are not hackable, are relatively cheap to produce, and cannot be read without a special microscope. The technique uses no energy once the data is recorded. The researchers believe data-storage methods like their innovative method using fluorescent dyes will become increasingly important in the 21st century. “In the future, we will need to store large amounts of data as our society transitions to a digital society,” Nagarkar said. Harvard licensed the technology to a new digital data storage company co-founded by the researchers, who are developing the method into a commercial product. The company is pursuing opportunities for partnerships with data storage providers. The research was published in ACS Central Science (www.doi.org/10.1021/acscentsci.1c007280).