• Physics 16, 125
Using carefully placed cuts, the scientists engineered an adhesive tape that is highly sticky but easy to remove.
M. Bartlett/Virginia Tech
Ubiquitous in first aid cabinets, it’s easy to take adhesive bandages for granted. But not all plasters are created equal and finding the perfect one is tricky: too sticky and the plaster can be painful to tear off, not sticky enough and it could come off before the wound can heal. Now Michael Bartlett of Virginia Tech in Blacksburg and colleagues may have solved the blindfold conundrum [1]. Using existing adhesive tape, the team shows that carefully placed U-shaped cuts in the tape can bond the tape both strongly and weakly to a surface, with the apparent strength depending on which end of the tape the user pulls when they want to remove it.
Most of today’s adhesive tapes are either strongly attached to a surface and therefore difficult to remove or slightly sticky and easy to tear. The researchers would like to create a tape that bonds tightly and is easy to remove. Such tape could allow tear-free removal of patches from children’s arms as well as secure packing of shipping boxes that can be easily opened. But engineering both qualities into a single material proved difficult.
For their demonstration, Bartlett and his colleagues cut the templates into readily available adhesives, including tape and gloves that provide extra grip to a surface. The researchers focused their tests on cuts that contained lines of connected features in the shape of the letter U, with the U measuring from a few cm to mm in width and height. The motifs were cut into the tape using a laser cutter.
M. Bartlett/Virginia Tech
The team found that the adhesion of the tape was highly dependent on the alignment of the pull direction with that of the United States. The strongest adhesion was found when the tape was lifted from the end which caused the tabs to detach in the opposite direction of the tape being pulled (Video 1). In this scenario, the tongues behave similar to someone pushing on their heels to avoid being dislodged, giving the tape a 60-fold increase in the strength of its adhesion. Conversely, when the direction of pull matched the direction of tongue lift, separation was easy and adhesion matched that of standard versions of the tape (Video 1).
The researchers also looked at their tape’s ability to withstand heavy loads using tests that included repeatedly dropping a standard cinder block on a taped box and using the tape to hang an object on the wall. They found that boxes sealed with a length of U-pattern packing tape withstood over five impacts from a dropped brick compared to two for patternless packing tape. The engineered tape also attached a frame to a wall for a longer time: seven days for the patterned adhesive (after which the researchers removed the image) versus 20 minutes for the standard version.
Bartlett notes that they were able to accommodate the superior strength of the adhesive by altering the height and width of the US and the positioning of the US relative to each other and to the ends of the tape. “This opens up some interesting possibilities for highly tunable adhesive films,” he says. Michal Budzik, a materials scientist at Aarhus University in Denmark, agrees. The ability to easily tailor a tape’s adhesive properties without changing its chemistry will “no doubt be influential,” he says. “This dramatic shift in adhesive research opens up new avenues and possibilities. I find it very promising.”
Now that Bartlett says he and his colleagues have demonstrated that their cutting technique works for tailoring tape and glove adhesion, Bartlett says the team plans to apply it to other systems. These include robotic grippers and medical devices, such as long-wear glucose monitors. “There are many possibilities,” he says.
Sarah Wells
Sarah Wells is a Boston-based freelance science journalist.
References
- D.Hwang et al.Metamaterial adhesives for programmable adhesion via reverse crack propagation, Nat. Mother. (2023).
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Image Source : physics.aps.org