DOE Pulse
  • Number 418  |
  • July 21, 2014

Curiosity and collaboration define Xiao-Ying Yu’s innovations

Xiao-Ying Yu holds SALVI, which enables vacuum-based instruments to analyze liquid surfaces in their natural state at the molecular level.

Xiao-Ying Yu holds SALVI, which enables
vacuum-based instruments to analyze liquid
surfaces in their natural state at the
molecular level.

While she enjoyed her education in China and across the United States, Dr. Xiao-Ying Yu believes that there is no substitute for working on projects where nobody knows the answer – yet. Working without a safety net, whether it be answers in the back of a book or an advisor who knows a sample’s contents, is what drives her. And, so far, it has led to chemical and atmospheric discoveries, along with a unique device that could dramatically expand the use of high-powered instruments.

“I tell my students not to take too many classes because they may not teach you how to solve problems that nobody else knows how to answer,” said Xiao-Ying, who regularly mentors students in her lab at DOE’s Pacific Northwest National Laboratory. “To answer an unknown, you need to learn how to learn and then work on it.”

Xiao-Ying’s curiosity led to SALVI, which stands for System for Analysis at the Liquid Vacuum Interface. Salvi is also a Spanish word meaning “saved from loss of water in vacuum.” Small enough to fit in the palm of your hand, this 2014 R&D 100 award winner is a unique tool that – for the first time – enables vacuum-based instruments to analyze liquid surfaces in their natural state at the molecular level. The challenge with vacuum-based instruments is that the liquid often evaporates before it can be analyzed. To prevent the sample from boiling away, scientists built specialized sample holders. Unfortunately, these holders were expensive and fit just one instrument.

To prevent evaporation, SALVI continuously pumps the sample, as little as two drops of liquid, through an extremely narrow channel that provides high linear velocity at the detection window. Instruments access the sample via a viewing port that allows an electron or other beams to access the sample. The result is clear images and chemical data on complex liquids.

“But it is not just about better pictures,” said Xiao-Ying. “We want to solve fundamental problems with applications – we want the answers to be used.”

And, SALVI is answering real-world questions. For example, it is being used to follow the reactions in a microbattery, providing data on the chemistry behind battery fading and probing the solid-electrolyte interface. Also, scientists at PNNL’s Institute for Integrated Catalysis are using SALVI to study carbon dioxide’s conversion to fuels. “Following the redox reactions and solvent changes gives scientists better insights into chemistry,” said Xiao-Ying. “And, it lets them design better catalysts.”

Because of its design, SALVI is instrument agnostic. It works in scanning electron microscopes, time-of-flight secondary ion mass spectrometry or ToF-SIMS, super-resolution fluorescence microscopes, confocal laser scanning microscopes, and other characterization techniques without being reconfigured.

Right now, Xiao-Ying and her colleagues are extending the capability to nuclear magnetic resonance spectrometry. Working with Dr. Ryan Renslow and others in DOE’s EMSL, Xiao-Ying is redesigning SALVI to remove any magnetic parts and to shrink the overall device down to fit in an NMR sample holder or small enough to seal inside a #2 pencil.

In another effort in bioimaging, Xiao-Ying’s team is collaborating with PNNL biologist Dr. Galya Orr and her team to enable correlative imaging of mammalian cells using super-resolution fluorescence microscopy and ToF-SIMS. Cells are cultured in the microfluidic channel followed by in situ chemical mapping. The new capability is intended to explore cellular interactions at the single cell level and potentially elucidate complex biological dynamics of relevance to DOE missions.

But, this is not the story of an overnight success or one person working alone. The project, funded by DOE’s Office of Basic Energy Sciences and EMSL Operations, began more than a decade ago. Building SALVI was a collaborative effort. Xiao-Ying worked with colleagues such as Bruce Harrer and Dr. Theva Thevuthasan, who helped guide the project in its early years. “This work is not just me,” said Xiao-Ying. “In science, to solve really hard problems, you need to work with others.”

SALVI was built and tested at DOE’s EMSL, a national scientific user facility at PNNL. “EMSL is unique and has all the tools necessary for fabrication in one place,” said Dr. Zihua Zhu, who led the ToF-SIMS measurements and data analysis on the project.

Xiao-Ying’s interest in science began at an early age. Both of her parents were chemists in her native China, and she found she was good at chemistry and enjoyed the learning process. “But, my mom didn’t want me to do chemistry because of the challenges involved,” said Xiao-Ying. “However, I felt that chemistry made me so adaptable. The fundamental training I received goes beyond just one field.”

Leaving her native China, Xiao-Ying went on to graduate school at the University of Michigan, where she studied the kinetics of water in clouds. She did a postdoctoral fellowship at Brookhaven National Laboratory and went on to join the staff of Colorado State University. She joined PNNL and began to work on atmospheric studies, PNNL’s Chemical Imaging Initiative, and the Lab’s Materials Synthesis and Simulation across Scales Initiative.

Xiao-Ying’s research and innovation are made more efficient, in part, by her 5-year-old son and 3-year-old daughter. When she was a graduate student and a postdoctoral fellow, she would spend every waking moment thinking about projects. Now, she finds that she is more focused and efficient at work so that she can make more time to romp through the park and watch movies with her kids and her husband Dr. Roger Rousseau.

Submitted by DOE's Pacific Northwest National Laboratory