News Release

Intelligence emerging from random polymer networks

Researchers from Osaka University, the University of Twente, and the Kyushu Institute of Technology report on a sulfonated polyaniline organic electrochemical network device for speech recognition

Peer-Reviewed Publication

Osaka University


image: Voice recognition using sulfonated polyaniline view more 

Credit: ©2021, Yuki Usami et al., Advanced Materials

Osaka, Japan – Reservoir computing (RC) tackles complex problems by mimicking the way information is processed in animal brains. It relies on a randomly connected network that serves as a reservoir for information and ultimately leads to more efficient outputs. For realizing RC directly in matter (instead of simulating it in a digital computer), numerous reservoir materials have been investigated to date. Now a team including researchers from Osaka University has designed a sulfonated polyaniline network for RC.

Neural networks in the brain use electrochemical signals carried by ions. Therefore, an electrochemical approach is a logical choice when choosing a material system for RC. Organic electrochemical field-effect transistors (OECFETs) are popular in bioelectronics; however, they have not yet been widely used for RC.

The key to the reservoir material is that it has rich (time-dependent) behavior and is disordered, which makes polymer materials an excellent option as they form random networks by themselves.

Polyaniline is a promising polymer for RC applications, because it is easy to polymerize, has good stability in the atmosphere, and has reversible doping/de-doping behavior, which means its conduction can be altered.

The researchers investigated sulfonated polyaniline (SPAN), which, in addition to the advantages of polyaniline, has high water-solubility and self-doping behavior. These make SPAN easier to work with and the doping more uniform.

“Atmospheric protons are injected directly into the polymer chain of SPAN, which causes it to conduct,” explains study lead author Yuki Usami. “This conduction can then be controlled by adjusting the humidity.”

The researchers used a simple drop-casting method to assemble the SPAN on gold electrodes to give an organic electrochemical network device (OEND).

The SPAN OEND was tested for RC by checking the waveform and assessing its performance in short-term memory tasks. Results of a test to see how well speech could be recognized achieved 70% accuracy. This ability of SPAN OEND was comparable with a software simulation of RC.

“We have shown that our SPAN OEND system can be applied in RC,” says study corresponding author Takuya Matsumoto. “Future steps to establish systems that do not rely on humidity will provide more practical options; however, the success of our SPAN-based system is a positive step for material-based reservoir computing, which is expected to have a significant impact on the next generation of artificial intelligence devices.”


The article, “In-materio reservoir computing in a sulfonated polyaniline network,” was published in Advanced Materials at DOI:

About Osaka University

Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation. Website:

About the University of Twente

The University of Twente was founded in 1961 as Technische Hogeschool Twente or (THT). The institution was later renamed to Universiteit Twente (University of Twente) in 1986, as the result of the changes in the Dutch Academic Education Act in 1984. The UT is a public technical university located in Enschede, Netherlands. The UT collaborates with Delft University of Technology, Eindhoven University of Technology and the Wageningen University and Research Centre under the umbrella of 4TU and is also a partner in the European Consortium of Innovative Universities (ECIU). The university has been placed in the top 250 universities in the world by multiple central ranking tables. In addition, the UT was ranked the best technical university in the Netherlands by Keuzegids Universiteiten, the most significant national university ranking. Website:

About Kyushu Institute of Technology
Kyushu Institute of Technology (Kyutech) is a Japanese national university which was originally founded in 1907 and opened in 1909 as a private institution called the Meiji College of Technology. Throughout more than 110 years of its history, Kyutech has been contributing to industrial development in Japan by research and education in engineering fields.
Currently Kyutech aims to foster inter-disciplinary and innovative research with its 11 research centers and 2 research units in various research fields such as space, environment, energy, AI, IoT, data science, LSI, robotics, biology. Kyutech also promotes international research collaborations with overseas universities for establishing international industry-academic alliance which brings Kyutech diverse research environment in its laboratories. In such diverse and inter-disciplinary environment, Kyutech has been recognized as the academic institution that launched the largest number of small satellites in the world since 2012, and still holds the top position until 2021.
Also, such environment enables Kyutech to contribute to engineering education nationally and globally. In 2017, the BIRDS satellite project, in which students from developing countries build and operate their countries’ first satellites, was awarded GEDC Airbus Diversity Award as the best example of bringing diversity to engineering education. Furthermore, one of the student project teams supported by Kyutech for its hands-on education won the 1st place in World Robot Summit (WRS) 2 years in a row for service robotics category.
For the future, Kyutech will continue contributing to local and global society by its technology, knowledge and education. Website:

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