Science & Technology (Commonwealth Union) – Materials can retain traces of their history—much like a sheet of paper that shows a crease after being unfolded, serving as a “memory” of the fold. These stored imprints can later be accessed and put to use in different ways. In daily life, for instance, a combination lock relies on recalling the precise sequence of dial turns to unlock, while memory-enabled materials help improve the safety of aircraft, boost the performance of electronics, and enhance the durability of bridges.
Now, researchers at Pennsylvania State University have shown that even ordinary adhesive tape possesses a unique form of material memory. It can record a series of multiple “memories,” which can be adjusted in strength or erased to make room for new ones.
The findings were recently reported in a study published in the New Journal of Physics.
Nathan Keim, who is an associate professor of physics at Penn State’s Eberly College of Science and the study’s lead researcher indicated that many materials or systems exhibit what is known as return-point memory, which enables them to store a sequence of past events.
He pointed out that a familiar example is a combination lock, which must recall the exact order of dial movements to function.
Keim noted that return-point memory typically depends on alternating inputs that drive deformation. For example, when using a combination lock, the dial is first turned clockwise to a specific number, then rotated back past zero in the opposite direction to register the next step. A key feature of this type of memory is that reversing the sequence at any stage brings the system back to an earlier state.
Keim indicated that they wanted to know whether there was a system capable of retaining a sequence of events without needing to switch the input direction.
He further indicated that in a combination lock, for example, if it is reset to zero after the first turn and rotate clockwise again, the stored information is erased.
The team aimed to create a method that could accumulate new memories without wiping out earlier ones.
Keim stated that they discovered that ordinary adhesive tape can record a sequence of multiple inputs using a single, consistent direction.
He pointed out that moreover, the intensity of these stored memories can be controlled — allowing them to adjust their strength — and they can also be cleared to restore the system to its original state.
The researchers created an automated system capable of lifting a strip of tape to a set distance after it has been lightly pressed onto a surface, and then placing it back down again.
Sebanti Chattopadhyay, a postdoctoral researcher in physics and the study’s lead author indicated that regular adhesive tape responds to pressure.
She further pointed out that the more force that is applied, the stronger it sticks and they discovered that partially peeling the tape creates a distinct line of stronger adhesion at the point where you stop, and this line remains when the tape is reapplied. Chattopadhyay indicated that by repeating the process with progressively shorter peel distances, you can form multiple lines that act as stored ‘memories.
The device also includes a sensor that records the force needed to peel the tape. These stored ‘memories’ can be read by peeling the tape beyond each line, which causes noticeable spikes in the force required at those specific points.
“Peeling past the lines erases them and resets the system,” explained Chattopadhyay. “But, we can also tune the strength of the memories, making them require different amounts of force to peel past, which means that each line could represent different information. We can even make some strong enough to persist after resetting the system.”
