Sticky Tape Stores Memories Like a Combination Lock, Without Electricity

Pull a strip of ordinary Scotch tape partway off a surface and set it back down. Nothing remarkable seems to happen. The tape lies flat, a little crinkled perhaps, the adhesive re-bonding to whatever substrate you peeled it from. But look closely, at the molecular level of the adhesive layer, and something has been written there: a record. A memory of exactly how far you pulled.

Peel it again, a shorter distance this time, and a second memory joins the first. Do it a third time, shorter still. The tape now holds three distinct records, nested inside each other like Russian dolls, readable in sequence by peeling the tape back past each stored stopping point and measuring the small spikes in the force required. Nathan Keim’s lab at Penn State has spent the last few years working out why.

What the Tape Remembers

The physics of what’s happening is, in principle, simple enough. “Ordinary tape is pressure sensitive,” says Sebanti Chattopadhyay, a postdoctoral scholar in physics and first author on the paper, published in the New Journal of Physics. “The harder you press it down, the more firmly it adheres to a surface.” When you peel the tape partway, the mechanics of peeling itself create a zone of intense compression just ahead of the peeling front, a consequence of the elastic stiffness of the tape’s plastic backing applying a torque to the adhesive layer as it lifts away. That compressed zone fuses the tape to the substrate more strongly than anywhere else. When you lay the tape back down, the line persists. It’s a physical imprint of the turning point, the place where the peel reversed.

Reading the memories back requires nothing more than peeling past each line in turn. “We found that peeling the tape partway results in a line of strong adhesion at the stopping point that remains when you lay the tape back down,” Chattopadhyay says. Each line, encountered during readout, registers as a spike that roughly doubles the force needed to continue peeling. The lines show up in reverse order: last written, first read, an architecture that turns out to matter quite a lot for what the tape can actually compute.

But the feature that makes this discovery genuinely unusual, at least within the physics of material memory, is the direction of the driving. “Many materials or systems have a property called return-point memory that allows them to remember a sequence of events,” says Keim, an associate professor of physics. Combination locks work this way; so do ferromagnets, sandstone, and a surprisingly wide range of disordered materials. In all of them, memory formation relies on the input alternating back and forth, the dial turning clockwise then counterclockwise, the magnetic field cycling between poles. “We were interested if there was a system that could demonstrate this ability to remember a series of events without alternating the input,” Keim says. Tape can. The peeling is unidirectional; the tape only lifts, never pushes. That means tape operates on a fundamentally different principle from every other well-studied memory-forming material, and Keim’s team has proposed a new theoretical framework (they call it “latching”) to describe it.

Tunable, Erasable, Possibly Useful

“We found that we could store the sequence of multiple memories with a single-directional input in ordinary adhesive tape,” Keim says. “And not only that, but that the strength of the memories is tunable,” he says, “meaning we can adjust how strong the memories are, and they can be erased to reset the system.”

The tuning is worth dwelling on, because most memory-forming systems in physics don’t offer it. Hold the tape taut at its turning point for around a hundred seconds before laying it back down, and the memory becomes significantly stronger (the compressed adhesive zone has more time to bond). Strong enough, in some cases, to survive being read out, leaving a ghost of itself in the tape’s adhesive layer that persists across multiple peeling cycles. Change the substrate from the tape’s own backing to smooth acrylic, and the memory is stronger still. “Peeling past the lines erases them and resets the system,” Chattopadhyay says, “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.”

This is, more or less, the definition of a writable, readable, and partially erasable data storage medium. A mechanical one, requiring no power source, no silicon, no lithography. Keim is at pains to be realistic about the implications. “We don’t expect that these devices will be made with adhesive tape,” he says, “but we are driven by a desire to understand the fundamental science underlying the various types of memories that materials can form and how they might apply in future systems.” The motivation, as he frames it, is foundational: work out what physical principles allow materials to store information at all, and the applications may eventually suggest themselves.

Computing Without a Circuit

There’s already a hint of what those applications might look like. Because the last memory formed in the tape is always the first one encountered during readout, the tape can, in effect, compare any new input to the one immediately preceding it. If you peel to a greater distance than last time, the tape reads out that previous memory during the encoding of the new one, providing a kind of instant comparison. If the new input is smaller, the tape simply writes a new memory without disturbing the old one. “This fact allows a simple type of mechanical computation,” Keim says. “It’s similar to a test used for working memory in neuroscience, called a one-back comparison.” In that test, subjects are shown a stream of stimuli and asked to compare each one to the previous item in the sequence, a task considered a basic index of working memory function. Tape does something functionally equivalent. Mechanically. Passively.

The analogy is more than just decorative. A motile organism searching for the direction of a chemical gradient, for instance, could in principle use this kind of one-back comparison to determine whether the concentration it’s currently sensing is higher or lower than the last sample it took, without needing a continuous record of time. Whether soft-matter systems in nature already exploit something like this principle is an open question.

“There has long been an interest in developing devices that don’t need electricity and don’t have the same vulnerabilities as electronic computers,” Keim says. Mechanical computers predate their electronic successors by centuries, and the idea of building computation into materials rather than circuits has seen renewed interest as researchers explore robotics, soft actuators, and sensing in environments where conventional electronics are impractical. What tape offers, for now, is a model system: unusually simple, unusually transparent in its physics, and amenable to the kind of systematic study that lets you vary one parameter at a time and watch what changes. The physics of pressure-sensitive adhesives has been studied for decades in the context of fracture mechanics. The memory behavior, it turns out, was hiding in plain sight on laboratory benches worldwide. “As this understanding grows,” Keim says, “we may find ways to use it that we can’t yet imagine.”

Source: Chattopadhyay et al., New Journal of Physics, 2026. doi:10.1088/1367-2630/ae4acc

Frequently Asked Questions

Is this actually a new discovery, or have people known tape has memory for a while?

The adhesive mechanics of tape have been studied for decades, but the specific memory behavior described here: multiple storable, tunable, erasable records encoded by unidirectional peeling: previously overlooked. What’s new isn’t the tape; it’s recognizing that its peeling physics constitute a distinct class of material memory operating on a different principle from everything else studied in the field.

Could materials like this eventually replace electronic memory in some applications?

Not tape itself, but the underlying principle could inform the design of mechanical memory systems that function without electricity. There’s genuine long-term interest in computation that doesn’t rely on silicon, particularly for soft robotics or sensing in environments where conventional electronics fail. The tape work establishes that purely mechanical systems can store and compare sequences of inputs, which is a foundational capability.

How does the tape actually “read” its own memories?

By measuring the force required to continue peeling. Each stored memory corresponds to a line of unusually strong adhesion in the tape, and when the peeling front crosses that line during readout, the force spikes noticeably, roughly doubling compared to baseline. The memories are read in reverse order of how they were written, which turns out to be what enables the one-back comparison computation.

What’s the limit on how many memories tape can store at once?

In principle, the capacity scales with the physical length of the tape, since each memory occupies a spatial region roughly a millimeter wide. The memories need to be separated enough that neighboring adhesion lines don’t interfere with each other. The researchers demonstrated reliable storage and retrieval of multiple memories in their experiments, but the theoretical upper limit for a given tape length remains a question for future work.