On October 7, NTT and the University of Tokyo announced that they had fabricated a proof of concept (POC) sensor device using batteries and circuits made of materials with low environmental impacts. They then generated transmission signals from this device for the first time in the world. As the internet of things (IoT) expands and more objects become connected devices, there is a concern that a lack of awareness will lead to their improper disposal as general waste. The successful results in this study arose from the group's efforts to address the issue of collecting, sorting, and disposing of these devices.
There is currently no clear definition of environmentally friendly devices or enough social consensus around this field. To address the issue, NTT intends for the project's results to be widely discussed. Furthermore, aiming for these ideas to be practically implemented in society, it will also collaborate with external organizations and companies to search for use cases for these environmentally friendly devices, producing new and innovative services. A portion of the study was published in the October 7 edition of Scientific Reports.
NTT has been aiming to address the issues of collecting, sorting, and disposal by promoting R&D of devices made of materials that have minimal impacts on the environment and living organisms after disposal. In 2018, the company demonstrated a concept for an environmentally friendly battery by creating the Tsuchinikaeru Battery (literally "Return-to-the-Earth-Battery"), composed of fertilizer and bio-derived materials.
For this project, NTT and the University of Tokyo furthered the concept of environmentally friendly batteries based on the idea that these devices should not contain precious metals or use chemicals that may affect humans, animals, and plants via the environment.
The group used organic semiconductor technologies--produced from organic instead of inorganic materials such as silicon--to fabricate circuits with low environmental impacts and confirmed that the circuits operate. By combining these environmentally friendly circuits with environmentally friendly batteries, the group generated transmission signals from a device with extremely low environmental impacts for the first time in the world.
For the study, researchers asked waste experts what materials should be used to achieve low impacts, addressing the issues of collection, sorting, and disposal to produce environmentally friendly sensors and devices consisting primarily of circuits and batteries.
Based on these expert opinions, NTT selected materials for the circuits and batteries based on two considerations: "Not using materials containing scarce elements" and "Not using hazardous substances." As a result, the materials chosen for this project were composed of just seven elements (H, C, N, O, Mg, Al, and S).
Next, the group fabricated circuits and batteries using the selected materials. The group developed the circuits in collaboration with the laboratory of Professor Jun Takeya at the Graduate School of Frontier Sciences, the University of Tokyo, which promotes research in the field of organic semiconductors. To achieve this, the group developed an organic transistor manufacturing process in which all electrodes are made of carbon material. These carbon-electrode organic transistors were then used to construct analog oscillation circuits and digital modulation circuits with CMOS.
The group then conducted demonstration tests by connecting commercially available speakers, oscilloscopes, environmentally friendly batteries, and cables to these analog transmitter circuits and digital modulation circuits. A breadboard was used to connect these components.
The fabricated device was assigned a 3-bit unique identification number. When the battery detects liquid, it generates electricity and energizes the circuits. This electricity produces a communication signal with a transmission frequency of 140 Hz superimposed on a 1-bit detection signal and a 3-bit identification number, and sound waves are generated from a speaker.
During the demonstration test, the circuit's output was measured with an oscilloscope, confirming that this environmentally friendly sensor was outputting a 4-bit communication signal.
Publication: Scientific Reports
Title: Electrostatically-sprayed carbon electrodes for high performance organic complementary circuits
This article has been translated by JST with permission from The Science News Ltd.(https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.