Ordinarily, adhesive tape either boasts a strong hold or is easy to remove. Drawing inspiration from an ancient paper-cutting technique, however, scientists have now devised a method of combining both qualities in existing types of tape.
Kirigami is a Japanese art form in which slits are strategically cut in flat sheets of paper, in such a way that the paper takes on a three-dimensional shape when pulled from either end. In recent years, we've seen it applied to innovations such as robotic grippers, no-slip shoe grips, and a snakelike robot.
In the case of the tape, a Virginia Tech team led by Assoc. Prof. Michael Bartlett cut rows of U-shaped slits into sheets of commercially available adhesive tape, then stuck those sheets to various surfaces.
When the scientists subsequently tried to peel the tape off by pulling it in one direction – coming up from the bottom of the U's – it exhibited 60 times more adhesive strength than unaltered tape of the same kind. When it was peeled in the opposite direction, however, it came off easily. Why was this so?
"An engineered cut can force the adhesive separation path to go backwards at specific locations, which we call reverse crack propagation, making the adhesive very strong," said Bartlett. "But by peeling in the opposite direction, it always goes forward, making it easy to remove. This is quite unusual behavior, but it is very useful to make strong yet releasable adhesives."
In lab tests, a brick was repeatedly dropped onto cardboard boxes which had been sealed on top with either regular or kirigami-cut tape. Whereas the former gave out after just two drops – allowing the box to collapse – the former lasted for at least five drops. Importantly, it was also found that different shapes and sizes of slits worked better for different types of tape.
Along with its use in secure yet easy-to-open boxes, other possible applications for the technique include robotic grippers, wearable health-monitoring devices, and products which are optimized for easy recycling.
"It is common to make adhesive bonds stronger but harder to remove," said Bartlett. "It’s also common to make those bonds less strong but easy to remove. The challenge is making it both stronger and still easy to remove, and that’s what we’ve achieved."
A paper on the research was recently published in the journal Nature Materials. The technique is demonstrated in the video below.
Source: Virginia Tech
