Science for our
Nation's
Energy Future

Energy Frontier Research Center

Community Website
Frontiers in
Energy Research
Newsletter
September 2011

A New Picture of Static Charging

Polymer surfaces show a mosaic of nanoscale charge domains upon the buildup of static electricity

Bryce Sadtler

(A) Possible scenarios for the distribution of static electrical charge after contact electrification between two surfaces. While the traditional view is that each material has a uniform surface of one charge type, the NERC scientists demonstrated that both surfaces possess a mosaic of positively and negatively charged regions. 

Scientists at the Non-equilibrium Energy Research Center, NERC, are challenging the conventional view of how static electricity exchanges between materials when brought into contact. They show that polymer surfaces possess a mosaic of static charge domains with positive and negative regions as opposed to a uniform surface of just one charge type. The work, led by Bartosz Grzybowski at Northwestern University and director of the NERC, was published in Science.

Examples of static charge buildup and discharge are all around us ranging from “static cling” when laundry is taken out of the dryer to lightning flashes during a storm. Static electricity is already used in commercial applications such as photocopying and laser printing. However, the insights of this work could enable the development of devices that store static charge and convert the electrical potential into useful forms of energy.

Contact electrification occurs when static charge is transferred between two insulating surfaces that are brought into contact and then separated. Generally, it was believed that the one of the materials develops a uniformly positive charge and the other, a uniformly negative charge. The NERC scientists used Kelvin force microscopy, or KFM, to study contact electrified polymer surfaces, where an atomically sharp conductive probe tip is scanned over the polymer and the potential offset between the tip and surface is measured at each point. This technique enabled the researchers to zoom in and image the surface charge potential with nanometer resolution (1 nanometer is about 100,000 times smaller than the diameter of a human hair).

While indeed the net charge of one of the polymers is positive and the other negative, the KFM images reveal that both surfaces display a mosaic pattern of positively and negatively charged regions that are only hundreds of nanometers in size. This means the charge density within any one of the nanoscale domains is about 100x greater than the net charge that would be measured over the entire surface.

“Knowing there is 100 times more static charge than ever previously measured turns our attention to this ‘hidden’ source of electrical energy,” said Bilge Baytekin, co-author of the article. “We would like to focus more on converting this electrical energy into chemical energy.”

The discovery demonstrates that the ability to probe material properties on the nanoscale can provide new insights and potential uses for everyday phenomena. In the future, one can imagine devices that capture the ambient static electricity that is normally wasted and use the highly charged surfaces to provide portable lighting or drive industrially important chemical reactions.

More Information

Baytekin HT, AZ Patashinski, M Branicki, B Baytekin, S Soh, and BA Grzybowski. 2011. "The Mosaic of Surface Charge in Contact Electrification." Science 333(6040), 308-312.DOI:10.1126/science.1201512.

Acknowledgments

This work was supported by the Non-Equilibrium Research Center, which is an Energy Frontier Research Center sponsored by the U.S. Department of Energy, Office of Basic Energy Sciences.

About the author(s):

  • Bryce Sadtler is a Beckman Postdoctoral Scholar at the California Institute of Technology and a member of the Light-Material Interactions in Energy Conversion, an Energy Frontier Research Center. His research interests are in light-driven processes for directing the morphology of inorganic structures and the design of nanoscale materials for energy conversion and storage.

Uncovering a Hidden Source of Electricity

Prevalence of static charge has scientists mulling over how to capture this potential energy source

The conventional view of contact electrification — when static charge is transferred between two surfaces — is that one surface is positively charged, and the other is negative. However, research shows that both surfaces possess a mosaic of positive and negative regions. This discovery could have implications for energy production.

What do freshly laundered towels and lightning strikes have in common? Both are examples of static electricity; in Science, researchers illustrate how static electricity could be a viable alternative energy source. Their study shows static charges are dense, with 100 times more static charge on a surface than previously measured. Also, the static is not distributed uniformly. Conventional wisdom says when dealing with static electricity, one surface develops a uniform positive charge and the other a uniform negative charge. The researchers used an advanced microscope technique to zoom in on statically charged polymer surfaces and found the charge actually forms a mosaic pattern. Discovering these details about static charge mosaics could have implications for energy production worldwide. The work was done by the Non-Equilibrium Research Center, led by Northwestern University.

More Information

Baytekin HT, AZ Patashinski, M Branicki, B Baytekin, S Soh, and BA Grzybowski. 2011. "The Mosaic of Surface Charge in Contact Electrification." Science 333(6040), 308-312.DOI:10.1126/science.1201512.

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.