A new adhesive that can let humans walk on walls

It may soon be possible to walk on walls like Spider-Man with American researchers claiming to have invented a device that could lead to development of shoes or gloves which would stick and unstick to walls and also bear loads.

It may soon be possible to walk on walls like Spider-Man with American researchers claiming to have invented a device that could lead to development of shoes or gloves which would stick and unstick to walls and also bear loads.

Researchers at Cornell University have created a palm-sized device that uses water surface tension as an adhesive bond,journal Proceedings of the National Academy of Sciences reported.

According to lead researcher Paul Steen,the device,using rapid adhesion mechanism,could lead to such development of the shoes or gloves that stick and unstick to walls,or post-it-like notes that can bear loads.

The team took inspiration from a beetle native to Florida,which can adhere to a leaf with a force 100 times its own weight,yet also instantly unstick itself.

The device consists of a flat plate patterned with holes,each on the order of microns (one-millionth of a meter).

A bottom plate holds a liquid reservoir,and in the middle is another porous layer. An electric field applied by a common 9-volt battery pumps water through the device and causes droplets to squeeze through the top layer.

The surface tension of the exposed droplets makes the device grip another surface — much the way two wet glass slides stick together.

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“In our everyday experience,these forces are relatively weak. But if you make a lot of them and can control them,like the beetle does,you can get strong adhesion forces,” Steen said.

For example,one of the researchers’ prototypes was made with about 1,000 300-micron-sized holes,and it can hold about 30 grams — more than 70 paper clips.

They found that as they scaled down the holes and packed more of them onto the device,the adhesion got stronger. They estimate,then,that a one-square-inch device with millions of 1-micron-sized holes could hold more than 15 pounds.

To turn the adhesion off,the electric field is simply reversed,and the water is pulled back through the pores,breaking the tiny “bridges” created between the device and the other surface by the individual droplets.

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The research builds on previously published work that demonstrated the efficacy of what’s called electro-osmotic pumping between surface tension-held interfaces,first by using just two larger water droplets.

One of the biggest challenges in making these devices work,Steen said,was keeping the droplets from coalescing,as water droplets tend to do when they get close together. To solve this,they designed their pump to resist water flow while it’s turned off.

The scientist envisions future prototypes on a grander scale,once the pump mechanism is perfected,and the adhesive bond can be made even stronger.