Deep sea plastics

ANAHEIM, CALIF. — Plastics are taking iPads to a whole new depth.

Using polycarbonate, polyether polyurethane and other materials, the creators behind iDive Inc. have developed a housing that not only protects tablet computers under water, but also provides a pressurized interior that allows researchers to actually use those tablets at depths of at least 330 feet, where water pressure is about 160 pounds per square inch.

“We don't know the limit, said Jim Peña, president of Inova Design Inc. of San Diego. “Theoretically, we could pressure-balance the inside with the outside for use at any depth.”

That capability isn't just the latest fad to keep up to date on your social media accounts. Instead, creator Michael Berumen, an associate professor of marine science at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia, developed the iDive so researchers could keep better records during surveys of fish, reefs and other underwater life.

In the past, researchers had to use special paper and a pencil during dives to record their counts, then feed each of those entries into a computer once they were back on land. That not only added tedious extra time to the research at hand, it was also the most common place for mistakes to occur, Berumen noted on iDive's website.

After coming up with the concept, Berumen and Peña connected initially at the 2012 Diving Equipment & Marketing Association trade show in Las Vegas.

Peña, a mechanical engineer, said it took about 14 months to design, tool and mold the parts, and another six months to demonstrate the feasibility. SolidWorks software was used during the development. Peña discussed the iDive housing in a presentation at a Society of Plastics Engineers' Western Plastics seminar in Anaheim in August.

While there are waterproof housings for cameras and smart phones, those housings don't allow users to actually interact with the apps and use the tablets for anything more than a simple recording device. To make the tablet actually work underwater, iDive safely encapsulates the tablet, then pressurizes the housing with either carbon dioxide canisters or air from another device such as a scuba tank.

The housing incorporates that pressurization system.

“We needed more pressure inside the housing than outside,” Peña said.

The lower housing is clear polycarbonate, and the touchscreen membrane is polyether polyurethane.

The solution for the high-pressure carbon-dioxide seal was Delrin acetal homopolymer.

“We could not get robustness with polyester PU,” Peña said.

Early experiments with touchscreen membrane materials pointed toward stiff PC or acrylic. Tests were conducted on sheets with thicknesses between 0.3 and 0.8 millimeters.

PC or acrylic easily transmitted a finger's conductive patch out of the water but failed underwater trials.

A screen's liquid crystal diode would sense a finger's small conductive patch above water but see a much larger patch underwater.

“This was because the material was inflexible and would contact the LCD with a large area even though the finger is small,” Peña said. “The finger plus water is more like putting your palm on the LCD.”

The designers explored using thinner acrylic or glass but found those materials lacked robustness for the application.

The membrane needed to be flexible, and the team changed its focus from stiff and strong materials to a flexible material.

“By choosing flexible material, we could retain a thickness of 0.3-0.5mm that seemed more robust for everyday handling,” Peña said. “With the basic idea of a thicker flexible material, I turned to plastic expert Eric Larson.”

Larson heads the material selection consultancy Art of Mass Production in San Diego.

Larson recalled “conversations with various suppliers, evaluation of elasticity versus flexibility, stretching versus elongation, aromatic polymer chemistry versus aliphatic polymer chemistry, evaluation of polyether and polyester chemistry, supply chain issues and more.”

Fwu Jih Die Casting Industrial Co. Ltd. of Tainan, Taiwan, die-casts the aluminum frame sandwiching the membrane and makes the precision machined parts.

Asia Optical Industries Ltd. of Hong Kong oversaw the tooling, injection molds the parts, assembles the housings and tests the systems. The tooling cost about $100,000, Peña said.

The iDive housing came onto the market in August 2014 and is available at a suggested retail price of $799.

About 600 units are in use with some for applications at the Scripps Institution of Oceanography in La Jolla, Calif., and Woods Hole Oceanographic Institution of Woods Hole, Mass., and others for members of the Professional Association of Diving Instructors.

Watershot Inc. of San Diego is the official distribution partner for the iDive housing.