In the lab, an electric field can control static charge on plastics

Most people have chipped lumps out of a protein shaker, or chased a floating clump around a mug of chocolate milk. Static electricity is one of the likely culprits. A team from RMIT University and Riga Technical University in Latvia has now shown, in the lab, that the static left on a surface can be controlled. Their study, published in Nature Communications, found that applying an electric field while two surfaces touch and then pull apart sets how much charge stays behind, whether that charge is positive or negative, or removes it altogether.

Static is usually something factories fight. Industry often adds expensive conductive additives as a one-size-fits-all fix, and the cost of static discharge is about US$5 billion in the electronics industry alone. The team's approach works differently: it tunes the charge rather than suppressing it everywhere. In the experiments, polystyrene films, a plastic, were pressed together and pulled apart 500 times while external fields were applied. Stronger fields left more charge, and reversing the field reversed the charge. The same behavior appeared in all the plastics tested.

The work also touches an old question: what makes charge separate when two materials touch and pull apart? Computer simulations showed that the fields the team applied were similar in strength to those created naturally when rough plastic surfaces press together. That supports the idea that tiny built-in electric fields help drive the separation of charge in everyday static electricity.

The authors list antistatic surfaces for manufacturing and electronics processing, control over where charged particles or plastics stick, smarter sensors and smart air and gas filters among possible uses. In one example, a conveyor belt sorting seeds could have its electric field adjusted to each species, so no seed gets a shock. The team plans to test the approach on real powders and to study programmable surfaces at much smaller scales. Its current grant application with industry partners targets fuels, where removing antistatic additives by tuning the surfaces they touch could make fuel more energy efficient. The team has announced no timetable for any of these uses. Sherrell says the next step is to find out how strong the field needs to be, how long to apply it to each powder, and where in the process it works best.

The limits are clear. Food powders such as protein, malt drink additives and coffee were not tested; the team used plastics and says its findings indicate how the approach could apply to food. The charge was set by applying a field during contact and measured afterward. Switching the charge live, as a conveyor would require, has not been demonstrated. The simulations use a simplified model, and the approach has not been tested on industrial equipment.