Reinventing Memory Storage: The Potential of Adhesive Tape
In the previous millennium, long before the digital revolution compressed entire albums and even movies into ultra-high-fidelity files that users could download in seconds, hundreds of millions of people relied on physical tapes to store albums on cassette (or 8-track) tapes and videos on low-resolution VHS cassettes. But what if sticky tape – not audio or video tape – was also a viable recording medium?
Exploring Mechanical Memory with Tape
“There has long been interest in developing devices that do not require electricity and do not have the same vulnerabilities as electronic computers,” says Nathan Keim, a physics professor at Pennsylvania State University. In a paper published in the New Journal of Physics, he and his co-authors delve into the soft matter physics of storing and recovering mechanical imprints following rearrangement or distortion. For example, how can partial peeling off and daily reapplication of adhesive tape mechanically store retrievable information? In other words, how can tape work as a memory material?
Currently, researchers and engineers use memory materials for a variety of purposes. For example, insulating vanadium dioxide can “remember” stimuli, including electrical currents, a valuable property for data storage and processing. Strong, reusable adhesives use temperature-activated shape memory polymers, and a liquid metal network rubber exoskeleton can, when heated, return to its full shape after being stored as a ball. Additionally, a textile made from wool waste can be programmed to morph into desired shapes for use in fashion, aerospace, and robotics, while robotic fabric can change the shape and stiffness of armor, self-erecting tents, and parachutes.
Innovative Memory System Design
For Keim and his colleagues, the goal is to design a memory material or mechanical memory system that can add memories without losing previous ones. A common example of a mechanical memory device is a combination lock, which, as Keim says, “must remember the sequence of turns of the dial to open,” using a property called return point memory.
In most point-of-return memory systems, the inputs reshaping the system must alternate, as when turning a combination lock one way and then another past the zero mark to form the next memory. Reversing the steps at any time in such a system returns it to its previous state, thereby clearing the memories (such as when one enters the wrong combination and rotates the dial past zero to resume the entry attempt).
Seeking to design a system that could “memorize a series of events without alternating inputs,” Keim’s team figured out how to “store the sequence of multiple memories with one-way input in ordinary tape” and learned that “the strength of the memories is adjustable—meaning we can adjust the strength of the memories—and they can be erased to reset the system.”
Testing the Limits of Adhesive Tape
Building an automated pressure-measuring device to peel off the tape at set distances and then reapply the tape helped the researchers demonstrate that “peeling off the tape halfway results in a line of strong adhesion at the stopping point that remains when you put the tape back down,” says physicist Sebanti Chattopadhyay, first author of the paper. “You can then repeat this several times by successively peeling off the tape over shorter distances, creating multiple lines or memories.” The device recovers memories by peeling the tape beyond the marked distances and measures the increased force required for peeling at each marker.
Postdoctoral researcher Sebanti Chattopadhyay prepares to load adhesive tape into the testing device
Future Implications
As Chattopadhyay explains, “Peeling off the lines erases them and resets the system. But we can also adjust the strength of the memories, which requires different strengths to peel them off, meaning each line can represent different information. We can even make some strong enough to persist after the system is reset.”
A key feature of tape memory, Keim explains, is that the information recorded last is always the first retrieved, which allows for “a simple type of mechanical calculation,” like “a test used for working memory in neuroscience called one-back comparison. Subjects are presented with a series of stimuli and asked to compare each of them with the previous stimulus. Because the last memory formed in the tape is always the one you encounter first during peeling, we can always compare a memory to the one that directly preceded it.”
Penn State’s research could one day help designers design electricity-free devices that can perform simple calculations without “the same vulnerabilities as electronic computers,” Keim says. Although he says such devices probably won’t be made from tape, discovering the secrets of memory materials will lead to useful developments “that we can’t yet imagine.”
Source: Pennsylvania State University
Here
“`
