Brazilian researchers make discoveries in electrostatics | AGÊNCIA FAPESP

Group discovers electricity derived from humidity and unveils mechanisms for producing energy through friction (photo: E.Alisson)

Brazilian researchers make discoveries in electrostatics

April 23, 2014

By Elton Alisson, in Beijing

Agência FAPESP – Despite its importance in understanding phenomena related to atmospheric electricity, such as lightning, and the fact that it gave rise to technologies such as photocopying, the field of electrostatics was stagnating until the past decade, owing to the absence of new theories and experimental techniques for properly identifying and classifying which entities, ions or electrons, confer a charge upon materials, according to specialists in that field.

A group of researchers from the National Institute for Research, Development and Innovation in Functional Complex Materials (INOMAT) – one of the national science and technology institutes (INCTs) jointly supported by FAPESP and the National Council for Scientific and Technological Development (CNPq) in the State of São Paulo – has made discoveries that will contribute to advancements in electrostatics.

Some of the principal findings of research carried out at INOMAT were presented on April 16 during the Brazil-China Symposium for Scientific Collaboration – FAPESP Week Beijing in Beijing, China.

The event, jointly promoted by FAPESP and Peking University (PKU) and holding sessions through April 18 in the Chinese capital, brings together researchers from the two countries to discuss studies in the fields of materials science, the environment, renewable energy, agriculture, life sciences, medicine and health, in the interest of developing scientific collaboration.

“The new models for electrostatic charge distribution have opened up possibilities for the development of materials that do not exhibit problems attributable to electrification, such as spontaneous fire, for example,” said Fernando Galembeck, a professor at the Chemistry Institute of the University of Campinas (Unicamp) and coordinator of INOMAT, in comments to Agência FAPESP.

“The discoveries in this field could also play a future role in energy production,” said Galembeck, who also heads the National Nanotechnology Laboratory (LNNANO) at the Brazilian Center for Research in Energy and Materials (CNPEM).

Researchers in Galembeck’s group at INOMAT have discovered in recent years that water in the atmosphere can acquire electric charges and transfer them to surfaces and other solid or liquid materials.

In an experiment in which they used tiny particles of silica and aluminum phosphate, the researchers demonstrated that, when exposed to high humidity, silica becomes more negatively charged, while aluminum phosphate acquires a positive charge.

The discovery of electricity derived from humidity – called “hygroelectricity” by the Brazilian researchers – has been described in a 2010 article in Langmuir, a journal published by the American Chemical Society.

According to Galembeck, the discovery has paved the way for developing “electrified water” – water with excess electric charge – under well-defined conditions, which may be useful for developing hydraulic systems.

“Instead of pressure, the signal used in a hydraulic system based on electrified water could be the electric potential of the water itself, but with very low current,” he explained.

Another, more remote, possibility would be the development of devices capable of collecting electricity directly from the atmosphere or from lightning. “We’ve made some attempts in that regard, but so far we have not obtained any interesting results,” Galembeck commented. “But the possibility of capturing electricity from the atmosphere does exist, and we have already described a capacitor that is spontaneously charged when exposed to humid air.”


The INOMAT research group’s most recent contribution to advancing our understanding of electrostatics was the unveiling of some of the mechanisms involved in triboelectrification, or production of electricity from friction.

Regarded as the most common electrostatic phenomenon, triboelectrification has been poorly understood, but new efforts to study it were initiated in the late 1990s, Galembeck said.

Through experiments with polytetrafluorethylene – a type of insulating polymer – the Brazilian researchers demonstrated that friction between the surfaces of conductive materials (dielectrics) produces patterns of fixed, stable electric charges with an irregular distribution on the two surfaces of the material.

According to Galembeck, the discovery demystified the idea that materials such as glass, synthetic fiber, wool and aluminum tend to acquire only a positive or only a negative charge when rubbed.

In a paper published in August 2013 in Scientific Reports – an open-access journal of the Nature group – the Brazilian group demonstrated that in some cases the principal component of friction is precisely triboelectrification. “Triboelectrification creates interactions between materials that increase, or even reduce, friction,” Galembeck said.

He notes that the discovery could play a role in the development of materials that are more resistant to wear caused by friction, such as brake linings and automobile tires, or that consume less energy.

“It is estimated that 30% of all the energy produced in the world is dissipated or wasted due to friction,” Galembeck pointed out. “If we were able to control friction in materials, it would be possible to consume less energy than we use today.”

The paper Charge partitioning at gas solid interfaces: humidity causes electricity buildup on metals (doi: 10.1021/la102494k) by Galembeck et al. can be read in the journal Langmuir at

Friction coefficient dependence on electrostatic tribocharging (doi: 10.1038/srep02384), also by Galembeck et al., can be read in the journal Scientific Reports at



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