CHICAGO — The intrusion of cellular phone rings into theaters, schools and nearly every other nook and cranny of modern life may soon hit a wall.

Playing to the backlash against ubiquitous communication, a company called NaturalNano is developing a special high-tech paint that relies on the wizardry of nanotechnology to create a system that locks out unwanted cell phone signals on demand.

The paint represents a dream to those who seek a distraction-free movie or concert experience, and a nightmare to those who compulsively monitor their BlackBerries.

It is also another breakthrough application of nanotechnology, the emerging science of harnessing submicroscopic organisms for everyday uses, like stain-resistant pants and transparent sunblock. The National Science Foundation has predicted that nanotechnology eventually will be a trillion-dollar industry.

"You could use this in a concert hall, allowing cell phones to work before the concert and during breaks, but shutting them down during the performance," said Michael Riedlinger, president of NaturalNano of Rochester, N.Y.

His firm has found a way to use nanotechnology to blend particles of copper into paint that can be brushed onto walls and effectively deflect radio signals.

The copper is inserted into nanotubes, which are ultratiny tubes that occur naturally in halloysite clay mined in Utah. The nanotubes are about 20,000 times thinner than a piece of paper, too small to be seen with even a conventional microscope. At this size, which is near the molecular scale, materials have different physical properties than they normally do.

By filling these tubes with nanoparticles 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.

Even the thought of such a thing upsets the wireless phone industry.

"We oppose any kind of blocking technology," said Joe Farren, spokesman for The Wireless Association, the leading cell phone trade group. "What about the young parents whose baby sitter is trying to call them, or the brain surgeon who needs notification of emergency surgery? These calls need to get through."

Farren said any scheme to selectively block calls is illegal.

But Robert Crowley of AMBIT Corp., which designed the radio-filtering device for NaturalNano, said the system is legal. The nanotech-augmented paint that blocks signals is a passive device, not an illegal radio jammer, he said.

The radio filter would allow all emergency radio communications to pass through the shield, Crowley said. With all other signals, like cell phones, the filter would act like a spigot to block or allow them to pass through — say, only during intermission.