Scientists are perfecting a paint that can switch between blocking and allowing cellular communication. The clever coating uses nanotubes filled with copper to do its magic, but the specifics weren't announced. The Chicago Tribune reports:
By filling these tubes with nano-particles of copper, the company can create a medium to suspend the signal-blocking metal throughout a can of paint without significantly changing the way the paint adheres to a surface.
NaturalNano will combine this signal-blocking paint scheme with a radio-filtering device that collects phone signals from outside a shielded space, allowing certain transmissions to proceed while blocking others.
Actively jamming cellular signals is illegal, but NaturalNano believes that because the paint acts passively it isn't illegal. Instead of jamming signals, the cell stopping paint is a filter that would still allow emergency radio frequencies through.