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Nanotechnology

Empowered: Lynn Loo on enhancing smart windows, building partnerships, and the humane drive behind engineering

The inventor of nanotransfer printing is working on an innovative, self-powering smart window.

13 July 2018, SPIE Newsroom. DOI: 10.1117/2.2201807.01

Lynn Loo interviewJust over 15 years ago, Yueh-Lin (Lynn) Loo invented nanotransfer printing, a method of transferring nanoscale features onto organic electronics and plastic circuits. A critical success as a scientific innovation, nanotransfer printing has contributed to the fabrication of devices as varied as capacitors, transistors, and epidermal sensors.

Loo's latest innovation lies in the development of self-powered smart windows. The director of the Andlinger Center for Energy and the Environment at Princeton University was trained as a polymer physicist; her focus is in materials science and materials physics, working primarily with organic polymers and semiconducting polymers. And her team's current work toward a self-powering smart window, requires multi-disciplinary expertise from chemistry, electrical engineering, and chemical engineering. "The group that's worked on this technology is very diverse for that reason," notes Loo, who will be giving a plenary presentation on "Making Smart Windows Smarter" at SPIE Optics + Photonics in San Diego on 21 August.

The self-described non-traditional chemical engineer says that her central interest is in understanding the particular molecule she's working with - its structure, how the structure develops, and then how the structural development process influences its macroscopic properties. "The macroscopic properties that we've been interested in is the opto-electronic properties of these molecules - mobility, conductivity, and, when you put [the materials] in a photovoltaic cell, how well they absorb light and generate current," says Loo. "Once we have that understanding, then we can say, ‘Oh, if this molecule instead now looks like that, it can improve the macroscopic properties by this much.' And we can proceed to make the second-generation material. So it's a derivative process: generating that understanding first; with that understanding comes a design rule; and then, with that design rule, you can go about and make something that performs better."

Her team's latest "something else" aims to free smart windows of cumbersome external electrical wiring. "A smart window can filter light or heat from coming into the building." Loo explains. "This tinting requires an electronic switch: if you apply a voltage similar to how you would turn lightbulbs on and off, you can switch between a mode that lets visible light in but not infrared heat - that would be useful on a summer day - or you can let in both light and heat on a cool winter day." Loo's innovation adds a transparent solar cell to the window in order to provide a self-powering element. "We've engineered our solar cells to be transparent in the visible range," she says. "We're prioritizing transparency so you can put it on an existing smart window. It absorbs UV light and generates power which can then regulate the transmission of light and heat from the visible and infrared into the building."

It was just last year that Loo and her team built and successfully demonstrated the self-powered smart window prototype, publishing their work in Nature Energy. "Because of the response to that paper," she says, "we founded a company to develop this technology. Among the challenges that we're trying to address are things like stability - windows need to last about 30 years. Also, we've demonstrated something that's about 10 cm squared: that's very small compared to a window footprint, so we need to translate our technology to large-area manufacturing.

Creating a startup is a new direction, but one that Loo clearly is serious about. "We do our work and file IPs as they come up," she says. "As an academic you often have to decide when it's time to turn that innovation over to somebody else. We usually come up with the IP, demonstrate something, and file the patent; interested companies license it and take it further. The idea is to use the materials we've made and the understanding we've gained to make, for example, a better glucose sensor, which a life science company had licensed. The smart windows IP will be licensed by our company because we think we can contribute further; that's why we're taking on the challenge of founding the company and developing further the technology ourselves."

That challenge fits seamlessly into an overarching priority that Loo holds dear. "As an engineer, you always have to think about how your work is going to impact society, how your work is going to better the lives of future generations," affirms Loo. "As academics, we're driven by intellectual curiosity, but as engineers, the first and foremost priority is, ‘Does the science contribute to the community?' So it's about marrying those things together. When my students pick a project, I always ask them, ‘What application do you have in mind?' They won't necessarily realize the application - they may make fundamental and important discoveries that put things onto a path to eventually realizing the application in the future - but their work should be driven by that larger picture: how will this better our lives in the future? "That's what makes us engineers."

Looking beyond your individual projects, too, toward something bigger, is also key. "Today's story, for me," says Loo, "is really about pushing the frontiers of collaboration and partnerships between academia and the private sector." She sees conferences such as SPIE Optics + Photonics as an opportunity to build such partnerships - "You can seed new collaborations, you can seed new ideas and build new partnerships" - but primarily she sees conference participation as an ambassadorial opportunity for the work that's being done in her group, particularly for the students who are doing the work: "Going out there and being able to tell people about the latest and newest discoveries that are being made in our lab, that's what I value most about going to conferences."

That said, she reminds young scientists to keep things in perspective. "It's easy to see the successes," Loo points out. "I tell my students when we give talks, not only are we ambassadors, we're storytellers. We don't tell the audience about the failures and our story does not reflect the incremental understanding over time. So it's very easy for students in the audience to think, ‘Ooh, science is so easy!' When science is not that easy! I mean, a PhD takes five years because you spend the first couple of years learning and making mistakes. Then, when you start being productive and you start understanding the problems that you're tackling, you start collecting useful data. There are going to be dark days when you're going to be challenged, so students need to understand and appreciate the value of being persistent and not giving up. That," says Loo, "is an important element of scientific discovery."

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