Memory device designed to function in wet environments

The devices are made using a liquid alloy of gallium and indium metals set into water-based gels, similar to gels used in biological research.

Conventional electronics are typically made of rigid, brittle materials and don’t function well in a wet environment. ‘Our memory device is soft and pliable, and functions extremely well in wet environments — similar to the human brain,’ said Dr Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of a paper describing the research.

In each of the memory device’s circuits, the metal alloy is the circuit’s electrode and sits on either side of a conductive piece of gel. When the alloy electrode is exposed to a positive charge it creates an oxidised skin that makes it resistive to electricity. When the electrode is exposed to a negative charge, the oxidised skin disappears, and it becomes conducive to electricity.

Normally, whenever a negative charge is applied to one side of the electrode, the positive charge would move to the other side and create another oxidised skin — meaning the electrode would always be resistive. To solve that problem, the researchers doped one side of the gel slab with a polymer that prevents the formation of a stable oxidised skin. That way, one electrode is always conducive — giving the device the binary capacity it needs for electronic memory.