Roy Gordon's Glass

It's an invention that has electrifying results

This is one of a series of reports on research discoveries at Harvard that have led to valuable commercial products and processes.

By William J. Cromie

Gazette Staff

Most people can't get through the day without encountering a special type of glass invented at Harvard.

It keeps heat inside in cold weather, outside in warm weather, conducts electricity, and resists wear much better than ordinary window glass. It is used to conserve energy, convert sunlight to electricity, and for everything from automobile mirrors to burglar alarms.

"It has more applications than I ever imagined when I started working on it," says the inventor, Roy Gordon, Thomas Dudley Cabot Professor of Chemistry.

In the 1970s, with the nation in an oil crisis, Gordon began researching glass that could dramatically reduce the energy needed for heating and air conditioning. When he asked the federal government to support his efforts, it refused, so Gordon continued the work on his own.

"I patented the invention and contacted every major glass-maker in the world until I found one that would commercially produce it," he recalls.

Unlike traditional glass, which is an electric insulator, Gordon's glass conducts electricity. That property makes it a natural for solar cells and calculators; frost-free supermarket freezer windows; and ATM, digital clock, and other small displays. The glass is now standard in bar-code readers and xerography-type copiers.

It's an option on some car models with sunroofs. Coupled with solar cells, the glass provides enough electricity to run a small fan to keep a parked vehicle cool in summer.

While experimenting with a glass to reflect summer sunlight from large office windows, Gordon came up with a new coating process that makes smaller, faster computer chips possible. Harvard is close to licensing that technology.

That same coating might someday be used to make more wear-resistant ball bearings and hip joints.

A Better Way

The idea for the glass came to Gordon in 1973 while he waited at an airport for a flight delayed by a refueling problem. At the time, oil and gasoline were expensive and in short supply due to an embargo by petroleum-exporting nations in the Middle East.

"I remember thinking, 'There's got to be a better way to power civilization than importing so much of our fuel from a source that's unreliable,' " Gordon said.

When he returned to Harvard, Gordon began looking into materials that might be used for energy conservation and solar energy. "Up to that point, I was doing theoretical chemistry, so this amounted to a substantial change in the direction of my work," he comments.

Gordon thought of coating windows so that they trapped more heat than they let escape. Such windows would provide a source of energy rather than an energy loss. Besides reflecting heat, the coating had to resist cleaning fluids and be transparent, durable, and cheap.

"I investigated a number of compounds and, largely by the process of elimination, settled on tin oxide," Gordon recalls. "Then I had to find a good way to get an even film of it on glass. By early 1975, I had solved the problem in the laboratory."

He applied for federal funds to further test and develop the technology, but the government turned him down. "I decided to go ahead and apply for a patent," Gordon said. "Then during a sabbatical, I traveled around to talk to any glass company that would listen."

Critics claimed that what worked on small glass samples in a lab could not be scaled up to commercial production. Factories make glass in 12-foot-wide ribbons as long as a quarter-mile. Getting a uniform coating on such massive sheets was impossible, they said. Gordon thought he could do it by a process known as chemical vapor deposition, wherein a gas of tin atoms and oxygen flows over heated glass.

Finally, in 1979, Libby-Owens-Ford (LOF) in Toledo agreed to try the technology on a factory scale.

Successfully scaling up the process required 10 years, twice as long as Gordon and LOF had thought. In 1989, the company began full-scale production of what came to be called Energy Advantage glass.

"The glass now is produced by all the major glass-makers," Gordon notes. It admits sunlight like ordinary window glass, and it prevents most of the heat in a room from escaping to the outside.

"The wholesale cost of the coated glass can be recovered in one year by the savings on heating bills," Gordon says. "It has already saved billions of dollars in fuel costs. Not burning as much fuel, in turn, prevents billions of pounds of pollutants from entering our air."

Glass Currents

But that was only the beginning. The energy-conserving function of the glass doesn't exploit its unique ability to conduct electricity.

"The conducting film can be etched into various patterns, so that an electric current sent across the glass lights up select numbers, letters, or designs," Gordon said. This makes it ideal for flat panel displays. At present, this capability is used for small displays, such as alarm clock faces, but he expects it will be scaled up to the size of television screens and larger displays.

When put on the glass plates of xerography-type copiers, the coating counters the buildup of static electricity, which can blur the images produced. A small current passed through coated windows on food-market freezers keeps frost from forming and lets you see clearly what's inside. A charged window or picture frame also makes an effective burglar alarm in a home, office, or art gallery.

Bar-code readers in stores across the country feature Gordon glass because it resists abrasion more than ordinary glass. Coated automobile mirrors douse the glare of headlights undimmed by inconsiderate drivers following behind you. "The list of applications is growing so fast, it surprises me," Gordon comments.

One of the largest potential uses is in solar cells, which convert the energy of sunlight to electricity. Several companies are producing solar cells with tin oxide coatings that conduct electricity from the cell to a circuit used for purposes such as lighting or heating.

"Solar electricity is too costly for homes, offices, and factories, but it is used in locations out of the reach of commercial power lines," Gordon points out. "Remote villages, warning beacons, and telecommunications relay stations now rely on it. Solar cells also keep vaccines and medical drugs cool in remote places."

There are stories around about people who grow marijuana indoors who have used it to avoid being detected via their high electric bills.

Chips and Joints

Gordon has continued his research on windows that save energy. He wants to keep out more summer heat and further reduce air-conditioning costs. His experiments indicate that a coating of titanium nitride reflects enough sunlight to cut energy use by two-thirds.

Titanium nitride forms a hard, antistatic coating that has many other uses, such as protecting semiconductors which are used as switches, amplifiers, and other circuit devices on computer chips. In some cases, such coatings are applied with a process that involves temperatures of 600 to 800 degrees. That's enough heat to damage the chips and the wires that connect the semiconductor devices. This problem is becoming more severe as manufacturers crowd as many as one million semiconductors on a chip the size of a postage stamp.

The National Science Foundation awarded Gordon a grant to investigate alternate ways to deposit films of titanium nitride. Building on the knowledge gained from his window research, he and his colleagues came up with a vapor deposition process that applies a uniform coating of the compound at temperatures between 300 and 400 degrees.

"In 1989, Harvard filed a patent application on this process," noted Kevin Heyeck of the Office for Technology and Trademark Licensing. "It is now undergoing commercial testing, and we are close to negotiating a license for the technology."

"We are also getting queries from industry about using the process for coating ball bearings and hip joints," Gordon adds. "Some of the metals used for these purposes change their properties for the worse when exposed to high heat. I believe this problem can be avoided with our kinder, gentler coating method."