Professor Choi Yang-kyu Develops Water-Dissolving Security Memory Device Within 10 Seconds
Produced using inkjet printing techniques on water-soluble paper soap

A research team led by Professor Yang-Kyu Choi of the Department of Electrical and Electronic Engineering at KAIST has developed a security memory device that can be dissolved in water and quickly disposed of.

The security non-volatile resistive random access memory (RRAM) developed by the research team is manufactured using an inkjet printing technique on water-soluble paper soap (Solid Sodium Glycerine: SSG). Stored information can be destroyed by dissolving it within about 10 seconds with a small amount of water.

This research, in which doctoral student Bae Hak-yeol participated as the first author, was published in the December 6th online edition of 'Scientific Reports,' a sister journal of Nature (Paper title: Physically transient memory on a rapidly dissoluble paper for security application).

In the past, the ability to stably maintain stored information for a long period was the primary indicator for gauging the performance of non-volatile memory devices. However, with the recent advent of the Internet of Things (IoT) era, where information can be easily shared anytime and anywhere, there is a growing demand for the development of security semiconductors capable of not only storing information but also fundamentally preventing data leakage.

To this end, meltable memory devices and fire-resistant security devices using paper substrates are being developed. However, existing meltable elements have limitations, such as taking a very long time to destroy and the burning technology requiring an ignition device and high temperatures.

To solve the problem, the research team succeeded in reducing the dissolution time to within seconds by fabricating a memory device on an SSG substrate that reacts and dissolves very quickly in water.


▲ The process of memory devices dissolving in water

This memory device is composed mainly of alkali metal elements sodium and glycerin and has hydrophilic groups, so it reacts with a small amount of water and decomposes.

Since soluble electronic devices can be vulnerable to heat and moisture, process conditions are critical. The research team deposited metal electrodes at room temperature and pressure using an inkjet printing technique with optimized viscosity and heat treatment conditions.

In addition, hafnium oxide (HfO2), which is a resistive switching layer that determines the characteristics of the memory device, was also deposited at a low temperature of 150 degrees or lower to obtain excellent memory characteristics. Through this, we fabricated a device that is stable at normal humidity but reacts only to a small amount of water.

The research team stated that the cost reduction effect is much greater than other security devices because they fabricated a two-terminal resistance change memory with a 'metal-insulator-metal' structure using a flexible paper soap-shaped SSG substrate and an inkjet printing technique.

"This technology can be manufactured at a cost one-tenth the level of existing silicon substrate-based technology by using resistance change memory devices," said doctoral student Bae Hak-yeol. "It can be quickly disposed of with a small amount of water, so it could be applied as a security device in the future."