New glass shoe sole for 'super' grip on ice

A new shoe sole, made up of glass fibres embedded in rubber, can provide a better grip on slippery surfaces such as ice, researchers including one of India-origin say.
Researchers are testing the material in an innovative, self-contained lab space that can be hoisted in the air and tilted to create sloped floors covered in ice and snow.
"I think anyone who has slipped or fallen on ice can testify that it is a painful or nerve-raking experience," said Reza Rizvi, a postdoctoral fellow at the Toronto Rehabilitation Institute.
"We need to give older adults better footwear so they feel confident maintaining their outdoor activity levels in the winter," said Tilak Dutta from the Toronto Rehabilitation Institute, a lead member of the research team.

Ice can be such a dangerous surface, Rizvi said, because when the temperature gets close to zero degrees Celsius, a thin, lubricating layer of liquid water easily forms on top of the ice.
Cleated footwear provides effective winter traction because the cleats dig into the still solid ice beneath the slippery layer of water, Rizvi said, but cleats can be dangerous if the wearer does not take them off as they go inside.

Cleats are very slippery on hard, wet marble or tile surfaces, for example, so a better solution for winter footwear is needed, researchers said.
Rizvi and his colleagues, including Hani Naguib from the University of Toronto, have developed a new method to manufacture a type of rubber that "digs in" on the micro-scale.

The material is made up of thermoplastic polyurethane, a rubbery plastic, embedded with tens of thousands of tiny glass fibres that protrude out of the rubber like microscopic studs and give the material the feel of fine sandpaper.
The material looks like regular rubber and will stretch and deform in similar ways, said Rizvi. The material also performs just as well as regular rubber on dry surfaces such as quarry tile, he added.
"The observed friction coefficients of the composites that we've developed would translate into fewer incidents of pedestrian slips," Rizvi said.
"Implementing these in our daily lives would reduce winter related injuries," said Rizvi.

Existing methods for fabricating the material require first extruding a rubber slab with glass fibres running parallel with the surface.
The slab is then cut and reoriented so that the fibres stick out of the surface like the pins in a pincushion.
The team has found a way to automate the process so that the material could be cheaply mass-produced.
The research was published in the journal Applied Physics Letters.