Memory device designed to function in wet environments

US researchers have developed a memory device that is soft and functions well in wet environments, thereby, opening the door to a new generation of biocompatible electronic devices.

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.

The device’s ability to function in wet environments and the biocompatibility of the gels means that the technology holds promise for interfacing electronics with biological systems such as cells, enzymes or tissue. ’These properties may be used for biological sensors or for medical monitoring,’ Dickey said.