Could the touch of a finger make mobile data storage more secure?
The agent was in trouble. She couldn’t let the files fall into enemy hands, but her capture seemed inevitable. And then, she remembered the kill switch. Pulling off a glove as she ran, she reached into her pocket and found the tiny pad on the surface of the flash memory drive. With that simple touch, she changed everything. Safe in the knowledge that the sensitive data was gone forever, she turned to meet her fate.
It’s perhaps not surprising that in this age of data security, there is a growing interest in transient electronic devices, which can be controllably destroyed or erased. To date, most transient techniques have focused on chemically processing the device, or applying a large external voltage in order to damage the semiconductor. While these options are effective at irrevocable data deletion, they also permanently destroy the device, meaning that it can never be reused.
In a new paper in Nano Energy [DOI: 10.1016/j.nanoen.2018.07.040], researchers from Korea’s Advanced Institute of Science and Technology report on their proof-of-concept – a flash memory device that can either be erased or destroyed using triboelectricity. The memory consists of junctionless silicon-oxide-nitride-oxide-silicon (SONOS) field-effect-transistors (FETs), assembled to form nine bits. The triboelectric ‘kill switch’ takes two materials from opposite ends of the triboelectric series – PTFE and Nylon. Bringing these two material into contact produces a significant voltage pulse that can alter the data stored on the memory, without the need for an external power source.
When a PTFE-gloved finger touches the exposed nylon pad, the contact-separation motion induces charge tunnelling, allowing holes to pass through the flash memory oxide. This simultaneously resets the memory, ‘soft-erasing’ the data, but allows the device to be reused. In contrast, the memory undergoes ‘hard destruction’ when the nylon pad is touched by a bare finger. In charge terms, the human body acts as a significant reservoir. Without the presence of an interface layer, that charge is instantly transferred to the memory, which permanently damages the gate dielectrics, deleting the stored data in the process.
Triboelectricity is usually considered an unwanted phenomenon in electronics, but this study suggests that, when properly harnessed, it could offer a route to irrecoverable data erasing for highly-secure mobile storage. The self-powered nature of the system may also be of interest to those developing small sensors for ‘Internet of Things’-based applications.
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Ik Kyeong Jin, Jun-Young Park, Byung-Hyun Lee, Seung-Bae Jeon, Il-Woong Tcho, Sang-Jae Park, Weon-Guk Kim, Joon-Kyu Han, Seung-Wook Lee, Seong-Yeon Kim, Hagyoul Bae, Daewon Kim, Yang-Kyu Choi. “Self-powered data erasing of nanoscaleflash memory by triboelectricity” Nano Energy 52 (2018) 63–70. DOI: 10.1016/j.nanoen.2018.07.040