Engineers create wood-based electronics circuits

Read More A group of engineers have created a new kind of chip for electronic devices that's made out of flexible wood pulp and can biodegrade in a matter of weeks.

A file photo of a semiconductor wafer.
Zigy Kaluzny | Getty Images
A file photo of a semiconductor wafer.

It's hoped that the development could someday help reduce the environmental impact from America's growing volume of discarded electronics. The flexible and transparent circuit also can be used in wearables and "smart" textiles. (Tweet This)

Consumers in the United States threw away 2.37 million tons of electronics in 2009, the most recent year for which data are available, and the country only recycled about 25 percent of that total, according to EPA estimates. About 152 million mobile phones were thrown away in that year alone. And that was in 2009.

"Many more gadgets may be discarded daily, considering the larger quantities and more varieties being produced in the recent years," the engineers wrote Tuesday in the journal Applied Physics Letters. "This will not only lead to a large amount of consumption of our limited natural resources, but also generate a large amount of waste that could pollute our environment."

Part of the problem with e-waste stems from types of materials used. For instance, the silicon or gallium arsenide-based chips that make up much of the guts of electronics contain materials that do not decompose well and can leach chemicals into soil and water supplies.

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"If you open up a mobile phone, you have a battery and you have chips," said Zhenqiang Ma, one of the authors on the study. "The hardest things to recycle are the chips themselves."

Another route to reducing e-waste, and to conserving potentially precious ingredients, may lie in developing biodegradable alternatives.

Silicon chips, for example, use much more silicon than they actually need, the researchers say. A standard 12-inch silicon wafer is about 775 micrometers thick, but only a tiny fraction of that thickness—one micrometer—is actually used by circuits. The rest of the wafer just provides physical support for the circuits—which is really a waste of silicon, Ma said.

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Ma and his colleagues at the University of Wisconsin and the USDA Forest Products Laboratory used a substrate made out of wood pulp, called "cellulose nanofibrillated fiber," and combined it with only the thinnest layer of silicon needed for the transistors that do the work on chips.

Cellulose nanofibrils have been around and used in other applications, but Ma and his team have demonstrated that the material can work at the frequencies that would make it useful for use in wireless devices.

The scientists say their material performed as well as conventional chip materials in their tests, and can biodegrade naturally over the course of several weeks with the help of fungi that are common in nature. The amount of silicon used is so minimal that it's far below the limits set by the Environmental Protection Agency, Ma told CNBC.

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Ma said he doubts manufacturers that make conventional chips will voluntarily replace their current materials with wood-based alternatives in the near future, since they have little incentive to bear the upfront costs of retooling. As with other so-called green technologies, such as LED lighting and solar panels, the government may have to create incentives to induce companies to invest in wood-based chips.

In the meantime, there are other opportunities for commercializing the technology.

The wood-based material is more transparent than glass and more flexible than silicon, Ma said, so it could be used to make chips for devices that can be curved or bent, such as wearables and "smart" textiles. Ma said his team has already applied for patents, and the technology is ready to be licensed.

"We are going to see a lot of electronics that will be flexible in the future," he said.