MATERIALS

Article on Tuning flexible circuits with light

Researchers from Osaka University and JOANNEUM RESEARCH MATERIALS created flexible integrated circuits precisely tuned by illuminating an organic polymer with ultraviolet light. This work may allow for inexpensive electronics to be incorporated into wearable sensors or computers. The research results were recently published in the journal Advanced Materials entitled "Heterogeneous functional dielectric patterns for charge carrier modulation in ultraflexible organic integrated circuits".

Schematic showing the process that allows for precise control of the organic transistor characteristics using light irradiation. The inset displays a photograph of the final device. Credit: Osaka University

 

A research team led by Osaka University (SANKEN - The Institute of Scientific and Industrial Research) in cooperation with the JOANNEUM RESEARCH Institute MATERIALS has shown how exposing an organic polymer to ultraviolet light can precisely modify its electronic properties. This work may aid in the commercialization of flexible electronics that can be used for real-time healthcare monitoring, along with data processing.

“While the integrated circuits inside your smart phone are quite impressive, they lack certain important features. Because the electronics are silicon based, they are very rigid, both in the literal sense of being inflexible, as well as having chemical properties that are not easily altered. Newer devices, including OLED displays, are made from carbon-based organic molecules with chemical properties than can be tuned by scientists to produce the most efficient circuits”, explains research group leader Barbara Stadlober. However, controlling the characteristics of organic transistors usually requires the integration of complex structures made of various materials.

Now, the researchers have used UV light to precisely change the chemical structure of a dielectric polymer called PNDPE. The light breaks specific bonds in the polymer, which can then rearrange into new versions, or create crosslinks between strands. The longer the light is on, the more the polymer get altered. By using a shadow mask, the UV light is applied to just the desired areas, tuning the circuit behavior. This method can pattern transistors of the desired threshold voltage with high spatial resolution using just a single material.

“We have succeeded in controlling the characteristics of organic integrated circuits using persistent light-induced changes in the molecular structure itself,” study corresponding author Takafumi Uemura explains.

“In the future, we may see smart versions of almost everything, from medicine bottles to safety vests. Meeting the computational demands of ‘the Internet of Things’ will very likely require flexible electronic solutions,” senior author Tsuyoshi Sekitani says. In particular, this technology can be applied to manufacturing methods for ultra-lightweight wearable healthcare devices.

The article, “Heterogeneous functional dielectric patterns for charge carrier modulation in ultraflexible organic integrated circuits” was published in Advanced Materials at DOI: https://onlinelibrary.wiley.com/doi/10.1002/adma.202104446