The cast is ventilated and washable thanks to its spiderweb-like membrane structure.
However, Mr Evill said it was still extremely strong, as the design was optimised to provide the most support at the point of fracture, while still supporting the whole arm.
On his website, Mr Evill said the cast would bring fracture support into the 21st century "after many centuries of splints and cumbersome plaster casts that have been the itchy and smelly bane of millions of children, adults and the aged alike''.
"The Cortex exoskeletal cast provides a highly technical and trauma zone localised support system that is fully ventilated, super light, shower friendly, hygienic, recyclable and stylish.''
Mr Evill said the cast was compact enough to wear under a shirt and suit jacket, unlike traditional casts.
He is reportedly looking for backing to develop the concept further.