'Squishy' Memory Device Utilizes Liquid Metal
Researchers created a memory device with the physical properties of Jell-O, using ions to change the state of the device's liquid metal components.
Credit: Michael Dickey, North Carolina State University

This Research in Action article was provided to LiveScience in partnership with the National Science Foundation.

Researchers from North Carolina State University created a memory device capable of functioning in wet environments that has the consistency of Jell-O ® — making it perfect for medical and implant use.

The innovation could open the door to a new generation of biocompatible electronic devices.

Prototypes of the device have not yet been optimized to hold significant amounts of memory, but work well in traditionally hostile environments. The devices are made using a liquid alloy of the metals gallium and indium, which are set into water-based gels, similar to those used in biological research.

The device's ability to function in wet environments and the biocompatibility of the gels mean that this technology holds promise to intertwine electronics with biological systems — such as cells, enzymes or tissue.

The device functions much like devices called "memristors" — resistors in which the flow of current in an electronic circuit is determined by the amount of charge that has previously flowed through it — and which some believe could be a possible next-generation memory technology.

The individual components of the new "squishy" memory device have two states: One that conducts electricity and one that does not. These two states can be used to represent the 1s and 0s used in binary language, the basis of practically all modern computer communication. Most conventional electronics use electrons to create these 1s and 0s in computer chips. The mushy memory device uses charged molecules called ions to do the same thing.

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 oxidized skin that makes it resistive to electricity. We'll call that the 0. When the electrode is exposed to a negative charge, the oxidized skin disappears, and it becomes conducive to electricity. We'll call that the 1.

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 oxidized 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 oxidized skin. That way one electrode is always conducive — giving the device the 1s and 0s it needs for electronic memory.

The paper, "Towards All-Soft Matter Circuits: Prototypes of Quasi-Liquid Devices with Memristor Characteristics," was published online July 4 in the journal Advanced Materials.

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