A research team at Virginia Tech has adapted kirigami, the ancient Japanese art of cutting
paper, into a method for increasing the adhesive bond of ordinary tape by 60 times.
Adhesive tape fulfills many purposes, from quickly fixing household appliances to ensuring
a reliable seal on a mailed package.
When using tape with a strong bond, removing it may only be possible by scraping and prying
at the tape's corners, hoping desperately that surface pieces don’t tear away with
the tape.
But what if you could make adhesives both strong and easily removable?
This seemingly paradoxical combination of properties could dramatically change applications
in robotic grasping, wearables for health monitoring, and manufacturing for assembly
and recycling.
Developing such adhesives may not be that far off through the latest research conducted
by the team of Michael Bartlett, assistant professor in the Department of Mechanical
Engineering at Virginia Tech, and published in Nature Materials.
Adhesive tapes were first developed in the 1920s to meet a need for automobile painters
who wanted better options for painting two colors on car bodies.
Since the first masking tape was put into use, many other variations have been created.
Factories have rolled out invisible tape for wrapping presents, electrical tape for covering
wires, and duct tape for more uses than it was ever intended to fill.
Normally, when tapes are peeled off, they separate in a straight line along the length
of the strip until the tape is completely removed.
Strong adhesives are made more difficult to peel, while reusable adhesives promote the
strength-limiting separation.
Bartlett’s team theorized that if the separation path were controlled, then perhaps adhesives
could be made both strong and removable.
They tapped into the methods of a 2,000-year-old Japanese art form to determine how to do it.
The art form of kirigami, through folding and cutting, can transform a flat sheet of
paper into a shape or even a three-dimensional object.
Children often use a basic form of this method when creating paper snowflakes.
But the research team was making more than snowflakes.
Because of kirigami’s artful origins, the method provided a framework for establishing
slices or cuts across an adhesive.
Bartlett’s team used these principles to engineer a series of U-shaped cuts.
Bartlett’s team found that applying these cuts made the bond of the tape stronger by
a factor of 60 while still allowing for easy removal by peeling in the opposite direction.
The team also found that the type of tape didn’t matter.
Kirigami increased the bonds of every type of tape tested, from packaging tapes to medical
tapes.
In all cases, strong adhesive bonds become even stronger and normally weaker adhesives
increased in strength, too.
The other interesting outcome of this approach is that it can be highly customized.
In a dramatic test for applications, the team applied the same type of tape to two cardboard
boxes, sealing them as one might for shipping.
One of the tapes had the application of kirigami cuts and the other did not.
Researchers then dropped a brick onto the lid of each box.
For the unaltered tape, the bond was broken after two drops, collapsing the lid of the
box and allowing the brick to enter.
However, the altered tape resisted the drops, and on the third attempt, the brick even bounced
off the lid.
In another test, the team boosted the sticky strength of objects other than tapes.
After applying kirigami cuts to a glove used by football players to catch the ball, the
researcher placed his gloved hand flatly on a sheet of plastic.
Both an altered and unaltered glove were abrasive enough for the researcher to hold the plastic
at a 90-degree angle, but the unaltered glove lost its bond after a few seconds.
The altered glove continued holding the plastic fast, until the researcher eventually laid
it down.
It is common to make adhesive bonds stronger but harder to remove.
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 the
researchers have achieved.