In the late 1990s, researchers from MIT developed a technique for testing the strength and elasticity of paper grips.
Now, in a paper published online March 1 in Proceedings of the National Academy of Sciences, MIT researchers have shown that the new technology can also accurately measure the force applied to a paper grip by a human hand.
The new technique, called diastIX paper grip test, measures the force that human hands exert to compress a paper clip to its peak.
“The paper grip is really critical for a lot of things,” said co-author Eric Dang, an associate professor of mechanical engineering and a graduate student in MIT’s Department of Mechanical Engineering.
“When you have a paper cut, there’s a very specific way to compress it.
For a paper to be as good as possible, you have to have good force transfer between the paper and the paper clip.”
The new paper grip tests on the other hand, measure the forces that human fingers and thumbs exert on a thin strip of paper.
“In this study, we were able to measure how much force a human finger would exert to cut a piece of paper,” Dang said.
“So, for a paper that was just cut, the human hand would exert about a thousand times the force required to do it.”
This means that a human thumb would have to exert about the same amount of force to cut paper as a human arm would exert.
In fact, the researchers used two different paper grips and found that a paper with a higher force density was significantly stronger than the other two.
The paper grip results are the first to measure the elasticity (the amount of elasticity that the paper can stretch or compress) of a paperclip in real time.
The research team’s goal was to test the paper grip technology on two other key parts of the paper’s structure: its surface and its surface tension.
They found that the surface tension of a new paper clip is dependent on how hard the paper is being compressed.
“We were able now to show that there is an important correlation between surface tension and the strength of the grip,” Dange said.
As a result, paper grip testing can help engineers better design and build high-performance, low-cost paper products, such as paper clip-wrapping devices.
“It was really an interesting step forward for the paper test technology,” Dangs said.
To test the diastX paper grip, the MIT team attached two devices to a piece in a test chamber and a paper sheet that was cut to a thickness of about 1/8th inch (25 microns).
The device placed a needle in a small slot in the side of the test sheet, and the needle pushed the test strip through a series of small holes in the test surface.
The device measured the force and the pressure exerted by the human thumb on the test piece of a thin sheet of paper that had been compressed to its full length.
The researchers then inserted a small pin into the slot, and an electrical signal was sent through the pin to a remote control.
They then measured the pressure at the tip of the pin, and then the pressure of the needle on the paper strip at the point where the pin was placed.
The pressure was measured for three different conditions, all of which were considered as “non-zero,” meaning that the pressure was zero.
The diastXP paper grip tested for the pressure that human fingertips exert to lift a thin piece of thin paper, with the maximum pressure observed at the end of the process.
In the second condition, the paper was compressed to a length of about 2.5 microns.
“There was a very high compression of the tape,” Danges said.
The force exerted on the thin paper was also significantly different from that of a human fingertip.
“If you’ve ever seen someone with a broken finger or a broken hand, it’s quite obvious that when the pressure is zero, they’re not able to lift it.
This is the opposite, because they’re able to press the paper up, lift it, and squeeze it.”
Dang says that the diaspex paper grip will be tested for many other uses in the future, including in medical devices that will be used to perform surgery and even to carry medical instruments around.
“These are really important things that are needed for people who need to be able to get things done with their hands,” Danches said.