Like air, water is one of our most important natural resources, something we need so fundamentally that most of us take it for granted and rarely give a thought to how it is assembled or functions on a physical level.
Researchers at the Department of Energy (DoE) feel differently, however, and have been studying the dynamics of water for many years, resulting in new observations about its viscosity that could pave the way for an advanced new class of liquid-based electronics.
A team of researchers led by the DoE’s Oak Ridge National Laboratory (ORNL) have used an advanced high-resolution X-ray technique to measure the strong bond involving a hydrogen atom sandwiched between two oxygen atoms—which is the essential chemical make-up of water. The bond is a quantum-mechanical phenomenon responsible for various properties of water, including viscosity, which determines a liquid’s resistance to flow or to change shape.
Though water is so abundant and intrinsic to life, its behavior at a molecular level has not historically been well understood. For many years it was thought that the collision of its molecules was controlling its dynamics—basically, how its molecules move around, said Takeshi Egami, a University of Tennessee-ORNL distinguished scientist and professor.
Using an advanced, high-resolution inelastic X-ray scattering technique, however, researchers were finally able to visualize the bond dynamics of water, discovering that it is the atomic bonding, not collision, that controls the dynamics, he told Design News.
“This experiment was designed to prove this idea, by actually seeing the bond dynamics of water,” Egami said. “My theory applies to liquids in general, but I chose water because it is such an important substance, the right actor to play the heroic role with brilliance and gravitas.”
An Oak Ridge National Laboratory (ORNL)-led research team used a sophisticated X-ray scattering technique to visualize and quantify the movement of water molecules in space and time, which provides new insights that may open pathways for liquid-based electronics. (Source: Jason Richards/ORNL, U.S. Department of Energy)
Previously, because the motion of water molecules is so fast, researchers studied them mostly by ultra-fast laser spectroscopy, which provided inconclusive results, he explained.
“This method gives us the idea of time-scale, but nothing about the real-space motion, because the wavelength of light is 1000 times longer than the molecular size,” Egami said.
Inelastic X-ray scattering—in particular, a pair-density function method that allows for visualization of static atomic correlations in crystals in real space—is a far better method for observing the molecules, he said. However, it only recently was possible thanks to instrumentation provided by SPring-8, a synchrotron radiation research facility in Japan that collaborated with Egami’s team.
“The instrumentation group led by A. Q. R. Baron of SPring-8 came up with fantastic set-up, which made it possible to achieve our dream,” Egami said. The team published a paper on their work in the journal Science Advances.
What the research proves is that it’s now possible to probe real-space, real-time dynamics of water and other liquids, Egami said. This opens the door for the development of new and advanced types of semiconductor devices with liquid electrolyte insulating layers, better batteries, and improved lubricants.
“Having succeeded in this goal, we now can explain the microscopic mechanism of viscous behavior of various liquids,” he said. “But the implication of this work is much wider. It showed that the local atomic dynamics can directly be observed. This approach will provide direct answers to numerous questions.”
The team recently completed a study of the water dynamics as a function of temperature, and has begun now to study the effect of adding salt as it continues its research, Egami told Design News. Future work could have a direct impact on the future design of electronics, he added.
“We will then study the dynamics of liquid electrolyte--highly polarizable liquid that could revolutionize the electronic industry by replacing oxide insulating films with a liquid electrolyte,” Egami said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years.