Mobile Computing

 

 

 

 

 

 

 

 

 

 

The figure illustrates a portable device that may weigh approximately one pound. Each of the display and keyboard are fabricated on a flexible substrate such as KAPTON. This substrate is laminated with a super-elastic material and arranged to spontaneously extend when the corresponding trapdoor is opened. When not in use it is rolled up and stored inside.

Superelasticity

One common super-elastic material is NITINOL, an alloy of nickel and titanium. The glass transition temperature can be adjusted by changing the stoichiometry. The phase transformation from martensite, a relatively softer material, to austenite, a relatively harder material, can be programmed to occur at say 10°C, below the normal operating temperature of a consumer device. The austenite phase is super-elastic, meaning it will resume its original shape if released. It is important not to exceed a certain strain threshold, typically a few percent, in order to retain the super-elastic effect over millions of cycles.

Researchers have recently reported progress with new super-elastic materials based on polymers rather than metals.