Printing Solar Cells and Wearable Sensors

Did you know that there is a machine in Seattle that can print solar cells, using a method that is much like printing newspaper? A long roll of plastic sheeting passes through the machine, which deposits silver-laden conductive ink to form electrodes, heats the ink to cure it, and then applies the active layer that converts energy from the sun into electricity. This technology, an exciting application for printed electronics, may very well pave the way toward affordable solar cells.

UW researchers using the Washington Clean Energy Testbeds’ roll-to-roll printer for solar cells, batteries, sensors, optical films, and other flexible, low-cost devices. Photo by Matt Hagen, courtesy of UW Clean Energy Institute.

UW researchers using the Washington Clean Energy Testbeds’ roll-to-roll printer for solar cells, batteries, sensors, optical films, and other flexible, low-cost devices. Photo by Matt Hagen, courtesy of UW Clean Energy Institute.

From 2011 to 2013 I wrote a regular column on printed electronics for Industrial Specialty + Printing Magazine, so I was especially excited to hear about the University of Washington’s newest venture. I’ve been wanting to tour the Washington Clean Energy Testbeds facility since it opened in February 2017, and in late September I finally got the chance to do so. I wrote a short piece about the Testbeds for Seattle Business magazine. My story appears in the December 2017 issue.

The Testbeds are part of the Clean Energy Institute at UW, founded in 2013 with funding from the WA state government. CEI started as a research institute solely for faculty and students, but CEI Director Dan Schwartz saw a great opportunity to connect with clean energy efforts in the surrounding region. The testbeds accomplish this. The facility provides the missing link: manufacturing at a scale that is compatible with commercial business.

The Testbeds facility is impressive and appeals to my inner materials science geek. The warehouse-like space, occupying an old sheet metal manufacturing plant near the university, currently inhabits 15,000 square feet of the building but has room to grow to 90,000 square feet. It is filled with equipment that makes up three different labs, each focusing on one of CEI’s primary focus areas –  solar energy, energy storage, and grid integration – chosen because of their importance to society and their ability to scale to commercial products. The solar energy lab contains the solar cell printing machine.

The Testbeds is staffed with people who have experience in both academia and manufacturing. The technical director, Devin MacKenzie, is a UW Professor with years of experience as an entrepreneur under his belt. He started the world’s first printed electronics company, Plastic Logic, in England at the turn of the 21st century.

In the early 2000s, many entrepreneurs envisioned printed electronics as the next big thing, but it hasn’t taken off as they hoped. The problem is that it has been difficult to making everything flexible, especially the computer chips needed to make flexible displays useful. Printed electronics is an efficient way to make large area products such as solar cells, or small, flexible components such as sensors. But it can’t yet produce high-powered microprocessors. The resolution isn’t good enough to reliably print small enough features as closely spaced as they are in high-end computer chips.

Before Devin became an entrepreneur, he earned a PhD in Materials Science and Engineering. His PhD research involved trying to produce blue and white LEDs based on compound semiconductors. These materials had to be processed at very high temperatures and involved some of the most toxic industrial gases used anywhere. The gases are so toxic that they are lethal below the minimum detection limits available. If you can detect it, it’s too late. The safety procedures in labs that process these gases obviously have to be extremely stringent.

Devin sees printed electronics as a much safer way to produce electronics, in addition to being able to create products that wouldn’t be possible using conventional processing. Printed electronics may also provide a route to improved worker safety in various industrial manufacturing industries, beyond semiconductor chips. A wearable patch could act as a sort of “dosimeter for everything.” Dosimeters detect exposure to radiation, and are encased in rigid holders. The patch of the future would be flexible and comfortable to wear. It would be embedded with printed sensors to detect and monitor levels of radiation, volatile organic compounds, particles of dust from sawing, and other potential toxins. Though such a patch isn’t yet commercially available, the technology exists to produce it and products are in development. Stay tuned.