Molecules like DNA are capable of storing large amounts of data without requiring an energy source, but accessing this molecular data is expensive and time consuming. Publishing May 16 in the Cell Press journal Chem, researchers have developed an alternative method to encode information in synthetic molecules, which they used to encode and then decode an 11-character password to unlock a computer.
"Molecules can store information for very long periods without needing power. Nature has given us the proof of principle that this works," says corresponding author and electrical engineer Praveen Pasupathy of the University of Texas at Austin. "This is the first attempt to write information in a building block of a plastic that can then be read back using electrical signals, which takes us a step closer to storing information in an everyday material."
Traditional storage devices like hard drives and flash drives have drawbacks, such as high maintenance costs, energy consumption, and short lifespans that make them unsuitable for long-term data archiving. Molecules could provide an alternative option, and prior studies have shown that DNA and synthetic polymers can be designed to effectively store information. However, decoding these molecules usually involves expensive pieces of equipment, for example, mass spectrometers.
To make molecular messages that are easier to write and read, the team decided to try a different approach: designing molecules that contain electrochemical information—a method that allows messages to be decoded using electrical signals.
"Our approach has the potential to be scaled down to smaller, more economical devices compared to traditional spectrometry-based systems," says senior author and chemist Eric Anslyn of the University of Texas at Austin. "It opens exciting prospects for interfacing chemical encoding with modern electronic systems and devices."
To start, the team built an alphabet of characters using four different monomers, or molecular building blocks with different electrochemical properties. Each character was composed of different combinations of the four monomers, which yielded a total of 256 possible characters. To test the method, they used the molecular alphabet to synthesize a chain-like polymer representing an 11-character password ('Dh&@dR%P0W¢'), which they subsequently decoded using a method based on the molecules' electrochemical properties.
The team's decoding method takes advantage of the fact that certain chain-like polymers can be broken down by removing one building block at a time from the end of the chain. Since the monomers were designed to have unique electrochemical properties, this step-by-step degradation results in electrical signals that can be used to decipher the sequential identity of the monomers within the polymer.
"The voltage gives you one piece of information —the identity of the monomer currently being degraded—and so we scan through different voltages and watch this movie of the molecule being broken down, which tells us which monomer is being degraded at which point in time," says Pasupathy. "Once we pinpoint which monomers are where, we can piece that together to get the identities of the characters in our encoded alphabet."
One downside of the method is that each molecular message can only be read once, since decoding the polymers involves degrading them. The decoding process also takes time—around 2.5 hours for the 11-character password—but the team are working on methods to speed up the process.
"While this method does not yet overcome the destructive or time-intensive aspects of sequencing, it takes a first step toward the ultimate goal of developing portable, integrated technologies for polymer-based data storage," says Anslyn. "The next step is to interface the polymers with integrated circuits, where the computer chips become the readout system for the stored information."
