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Chemistry and physics

Electricity – In the air, in the water, everywhere

Electric charge model developed at Unicamp indicates there are no neutral materials

Eduardo CesarMicroscope used to analyze electric charges in materialsEduardo Cesar

Twelve years ago, chemist Fernando Galembeck found electric charges spread over the surface and interior of natural and synthetic latex particles and films. The charges were not supposed to be there, but they were, contrary to the alleged truth that plastic materials used in furniture and computers are electrically neutral. By collecting similar results, Galembeck and his team at the Chemistry Institute of the State University of Campinas (Unicamp) developed a set of learnings derived from hypotheses, discoveries and demonstrations – a scientific model – on the assiduousness and interactions of positive or negative electric charges in supposedly neutral bodies.

The concepts that are emerging at Unicamp and at American universities expand the possibilities of studies about the interaction of materials among themselves and with the environment – given that the air and its moisture can also carry electric charges – explaining why lightning is formed, for example. They also inspired the construction of new equipment. In 2007, the discoveries of Lawrence Schein, an American physicist and former researcher at Xerox and IBM, regarding particles with electric charges led to the creation of a firm in Taiwan to develop colored laser printing technology – today’s colored printers are three times as expensive as the black-and-white ones.

Besides the laser printers, static electricity underlies the operation of copying machines and of a type of painting that protects refrigerators and cookers from the effects of constant temperature changes. Electrostatic discharges can destroy computer chips, get in the way of TV transmissions or cause fires and explosions in factories, dirigible balloons or rockets, such as the Brazilian satellite launching vehicle in 2003. It can also give one a fright, when one gets a shock from touching a door handle on a dry day. When he caused the electricity from a lightening bolt to pass through the line of a paper kite, Benjamin Franklin not only entered history as an inventor (later he would also do so as president of Pennsylvania and one of the United States’ founding fathers), but also introduced to the world a form of energy that is now expanding much further.

Two centuries later, taking parallel paths, certain scientists such as Galembeck and chemist George Whitesides, who coordinates a research group at Harvard University, in the United States, are reaching the same conclusion: nothing is electrically neutral. In 2007, Whitesides co-authored an article published in the Journal of the American Chemical Society, which invited one to revisit the principle of electrical neutrality, as taught at colleges and universities to students of chemistry, physics and engineering. In 2008, in another study, Whitesides also signed the following statement: “Any material that has ions [particles with electric charges that are predominantly positive or negative] on their surface or in their interior may become an ionic electret” [electrets are materials with an permanent electrical field on the surface, whose relation to static electricity is akin to that of magnets to electromagnetism.] “When this material enters into contact with another one, the ions can move from one to the other.”

New ideas
We’re electric; everything’s electric”, summarizes Galembeck. In his lab, to show how electric charges circulate imperceptibly, he touches with his finger a silicon plate with an electric charge that generates a 267 volt potential, as measured by a voltmeter. “I didn’t die by electrocution because the charges are not in motion”, he explains cheerfully. “But I would have been electrocuted had I touched this electrode here, which measures the electricity of the plate generating an electrical potential of the same intensity.” Electric charges are static, which explains why we don’t get shocks all the time when we touch things that used to be seen as neutral, but that are not that static: they can penetrate deep within materials or attract opposite charges, as he and his team have shown by examining almost 50 different materials under a modified atomic force microscope, which identifies the electric charge fluctuation on a surface.

Little by little, the results have led to new ideas and hypotheses about phenomena for which there are few explanations. People who have suffered a heart attack, for instance, cannot have anything in their hearts or arteries made of polyethylene or polypropylene, as these may cause clots and block the blood flow. “Perhaps these polymers, that are normally negative, attract positively charged charges that circulate in the blood”, proposes Galembeck. “If this is the cause and if we manage to control the electric charge, perhaps new, better materials may appear, with many applications.”

Twelve years of analyses of organic compounds such as polymers (latex) and pulp, or inorganic materials, such as minerals, indicated that the special distribution of fixed charges is always very irregular. “Electric charges pepper the surface of materials, forming stains such as those on a jaguar”, compares Galembeck. “In the past, we used to think that all materials were uniform, like a cougar.” Under the microscope, the surface of these materials looks like the yellowish landscapes of the surface of Mars, transmitted by the Phoenix probe in 2008, with paler regions, that correspond to positive charges, intermixed with darker regions, with negative charges. The titanium oxide deposited on mica is an exception among such irregular forms: it is almost entirely dark, with only a few pale stains.

A plastic called hydroxyethyl methacrylate polystyrene (PS-Hema) is another exception, because of its particles’ beehive-shaped structure. When they examined this material, André Herzog, André Galembeck, Carlos Costa and Camila Rezende, all  chemists in Galembeck’s team, found beehives within these beehives with electrical charge variations even in areas of 1 micron by 1 micron (1 thousandth of a millimeter). “The fact that an area is negative doesn’t mean that the entire sample is negative”, explains Camila. The microscope reveals details from the so-called electric maps, whereas a macroscope, installed within an aluminum box with a pen-like sensor – all of it created by the researchers themselves – provides the electrical identify of the materials. In equilibrium potential, after the electrical charges settles down, the polypropylene has a negative 7 volts, whereas the polystyrene has a negative 5 volts.

UNICAMPStructure of a type of polystyrene has a beehive structure within a beehive structureUNICAMP

Excesses
Studies conducted to date at Unicamp show that in synthetic latex the negative charges result from an excess of chloride (Cl) or sulphate (-SO4, in this case with only one negative charge, rather than two, because it is bound to a molecule to which others are also bound, forming the long chain that characterizes latex) and phosphate (PO4, with only one negative charge for the same reason that applies to sulphate), while the positive charges indicate an excess of potassium ions (K+) or sodium ions (Na+). According to Galembeck, positive ions are traces of the substances that initiated the formation of the latex, and that remained alone without binding onto to the latex particles. Natural rubber, on the other hand, according to the doctoral thesis of chemist Márcia Maria Rippel, completed in 2005, may have regions with an excess of positive charges, resulting from a local abundance of calcium, sodium and potassium (Ca2+, Na+ e K+), or of negative charges, with proteins and phospholipids (substances similar to milk and soy lecithin).

The supposed electrical neutrality of the air and water has also vanished. According to a review study by Camila, Rúbia Gouveia, Marcelo Silva and Galembeck, positive and negative ions may form in the air, as a result of radioactive emissions from minerals such as radon, from the Sun or from space, as well as from the electrical field between the Earth’s surface (negative) and the ionosphere (positive). According to this line of thought, water stops being an agglomeration of neutral H2O molecules and becomes a mixture of H2O, positive hydronium ions (H3O+) and negative hydroxyl ions (OH). The Earth’s most abundant liquid thus acquires the role of storing electricity.

One of the consequences of this is that water also become cohesive. “With a few ions, water can stick anything to anything”, says Galembeck.

Leonardo Valadares, a chemist in Galembeck’s team, coordinated an experiment that evidenced some of these possibilities. Materials that normally do not mix – silica, a polymer, a mineral rich in calcium and titanium dioxide, all were found to mix after being dispersed in water, dried and examined under an electron microscope, according to a study published in 2008 in the Journal of Physical Chemistry. The Unicamp group is analyzing the possibility of interaction of the positive and negative water ions with other materials, while Whitesides’s group is focusing on OH. Both are exploring the possibility of building devices based on these concepts: Whitesides showed how to make new electrets (that capture electrical charges) with polystyrene in the Journal of the American Chemistry Society in February of 2007; and in February of the current year, the teams from Unicamp and from the University of Sheffield in England describe in Langmuir particles of silica and polystyrene that are strongly cohesive and form in the presence of water.

Electrical water
Water has been shown to have another property: besides carrying the electric charges of other materials, it can itself be the source of an electric charge. At the University of Washington in Seattle, USA, Gerald Pollock and Kate Ovchinnikova examined the capacity of water to become electrified briefly, in an article published in November 2008 in Langmuir, a major international scientific journal in the field of physical chemistry, with an interrogative title: “Can water store charge?”. They saw that the electrical current in water lasted for ten minutes after the negative and positive poles of the electric current – the electrodes – had been disconnected. The researchers concluded that water “seems to have” the capability to store and distribute an electric charge. The author’s careful wording is what seems excessive, given that they say that they picked up with equipment most of the electric charge separated in the water.

Regarding water as a source of electricity helps one to understand phenomena in the atmosphere such as the forming of lightning bolts, which are triggered by electric charges released by the clouds themselves. “If one could control this static electricity to the point of avoiding the lightning bolt…”, imagines Galembeck. “All we have achieved to date is to try and draw the bolts to lightning conductors”. In the clouds themselves, there is an accumulation and a separation of electric charges, which is more easily understood if one looks upon the planet’s most abounding liquid as a broth of ions – the positive ones normally at a higher altitude than the negative ones.

“There is an electrical field in the atmosphere”, he says, in his quest for explanations for the separation of electrical charges within clouds. “The ionosphere [the highest layers of the atmosphere] is mainly positive, whereas the Earth is mainly negative.” One of his group’s experiments showed that the water in the atmosphere plays an important role in the electrification of materials, because it transfers ions: the simple fact of a paper sheet being moved from higher humidity to lower humidity is sufficient to change the electrification state. “Bodies can interact with the space around them, gaining or releasing electrical charge”, comments Galembeck.

Explanations are also appearing for the fact that normally innocuous powders, such as sugar and flour, can explode as a result of uncontrolled electrification – one of the greatest industrial accidents in the United States, which took place in 2003 in a surgical materials factory and  killed 16 people resulted from polyethylene dust accumulating in the air-conditioning ducts, becoming electrified and exploding. “Dust can explode more easily than other materials because of its greater surface of interaction with water ions in the atmosphere.” This is not enough, however, because our knowledge gaps are still vast. “Does this plastic”, says Galembeck pointing to the Formica that lines the cabinet next to where he is sitting, “absorb more OH- or H+ from the humidity in the air? And what will happen as a result of interaction with one ion, or with the other? I’m assuming that it does not absorb them in the same proportion. It also absorbs water, but there must be a partition, a separation of the ions.”

Even the most basic questions still lack satisfactory answers: why do the charges appear? Why does a body become electrified? What makes a charge that is normally stationary have an effect? “Not only electrons bear charges”, suspects Camila. For Galembeck, static electricity has generated enterprises and the millionaire copying machine and printer business, but progress now depends on new concepts and ideas. “We need to move beyond the current state of affairs, which is the worst possible one: when people don’t know  but think they do.” In an article in Science, published in 2007, with the authority of someone who has worked in innovative firms, Schein expanded beyond academia his quest for answers: “We must understand how the charges appear and how the electromagnetic forces behave.”

Clouds
After years of silence in the search for explanations for the “outlaw” results he collected, Galembeck can now celebrate a work strategy that has born fruit: keeping track of current scientific themes while also getting off the beaten track. “I got no encouragement, nor any specific funding for studies on static electricity, but I did have autonomy”, he tells us. “I made use of information and leftover equipment from other projects.” With experimental results, articles and new ideas at hand, he now feels at ease to explain situations that have intrigued him for quite a while. “Why are the shapes of clouds of water so different from those formed when burning vegetation? Perhaps because of the separation of ions.”

He does not hesitate to come down from the clouds for an experiment [which can be seen on YouTube] that physics professor Walter Lewin usually shows his students at MIT, the Massachusetts Institute of Technology: from two taps, water drips through a metal cylinder and falls into separate cans. From each can, there is rigid line leaving, which ends in a sphere. The spheres at the ends of the lines almost touch. A few seconds after the water starts dripping, the spheres release an electric spark. How can one explain this? “According to Professor Lewin’s lecture, which is on the Internet, the water that accumulates at the bottom is electrified and capable of causing an electrical discharge in the air. This phenomenon, so simple and known since the times of Kelvin, might be a source of electric power, but it isn’t, because it isn’t properly understood. Where does this electricity come from?” Galembeck proposes a new explanation: “The water, as it drips, evaporates in part, retaining more positive or negative ions.” Would anybody else like to take the risk of coming up with an explanation?

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