- Direct integration of an HfOx charge trap layer with an organic semiconductor… Overcoming limitations in flexibility and stability 

- Physical Reservoir Computing (PRC) successfully applied to biosignal processing and hand-gesture recognition

- Published in the prestigious international journal npj Flexible Electronics... IF: 15.4, top 1.8% in JCR

A research team led by Professors Dong-Wook Park and Yoon Kim from the School of Electrical and Computer Engineering at the University of Seoul has successfully developed an “organic–inorganic hybrid charge-trap synaptic device” for next-generation wearable and bio-integrated computing.

This research successfully mimicked the key functions of biological synapses and demonstrated excellent performance as hardware for temporal information processing based on Physical Reservoir Computing (PRC). The findings of this research, recognized for its academic value, were published in the prestigious international journal npj Flexible Electronics, which has an Impact Factor (IF) of 15.4 and ranks in the top 1.8% in JCR.

To overcome the limited flexibility and stability of conventional neuromorphic devices, the research team adopted a hybrid structure in which an inorganic channel trap layer (HfOx) and an organic semiconductor channel (DPP-DTT) were fabricated on a flexible, biocompatible substrate (Parylene-C). The proposed device simultaneously achieves the excellent flexibility of organic semiconductors and the high stability of inorganic materials and realizes a transient charge trapping/detrapping mechanism, in which channel charges are spontaneously trapped and released repeatedly, through abundant charge traps formed at the organic–inorganic interface. This operating principle is essentially identical to the transient changes in conductivity observed in brain synapses, thereby successfully mimicking short-term plasticity (STP), a key characteristic of biological synapses.

△Schematic diagram of the DPP-DTT, HfOx, and Parylene-C-based synaptic device structure and the concept of Physical Reservoir Computing (PRC) implemented using the device

△Architecture for surface electromyography–based (sEMG-based) hand-gesture classification using a Physical Reservoir Computing (PRC) system

Furthermore, the research team constructed a Physical Reservoir Computing (PRC) system based on the device and applied it to surface electromyography (sEMG) signal processing. As a result, the system classified complex hand gestures—including ring-finger (87.0%) and little-finger (87.4%) flexion—with high accuracy and also demonstrated high recognition accuracy in MNIST digit classification.

In this study, Kyeungbin Kim, a researcher at the University of Seoul (co-first author), was responsible for the overall design and fabrication of the organic–inorganic hybrid synaptic device and conducted short-term plasticity measurements and device physics analysis. Boram Kim (co-first author) designed a Physical Reservoir Computing system based on the device’s nonlinear dynamic characteristics and led MNIST digit classification and sEMG-based hand-gesture recognition simulations. 

△ Simulation results for MNIST digit image pattern recognition and classification using a Physical Reservoir Computing (PRC) system

Professor Dong-Wook Park (corresponding author) explained the significance of the research, stating, “The hybrid device developed in this study combines the excellent flexibility of organic materials with the reliability of inorganic materials, providing a low-power, high-efficiency solution for overcoming the von Neumann bottleneck of conventional computing architectures.”

Professor Yoon Kim (corresponding author) added, “As we have demonstrated that the device can effectively process complex biological signals that change in real time, it is expected to become a key enabling technology for next-generation flexible neuromorphic hardware in applications such as edge computing, real-time signal analysis, and adaptive sensing systems.”

Meanwhile, this research was conducted with support from the Ministry of Science and ICT and the National Research Foundation of Korea (NRF) through the Global Fundamental Research Laboratory Support Project, Mid-Career Researcher Program, and National Agenda Research Project. It also received infrastructure support from the Information Technology Research Center (ITRC) support program of the Institute for Information & Communications Technology Planning & Evaluation (IITP), the IC Design Education Center (IDEC), and the Center for Semiconductor Research at the University of Seoul (UOS Fab).

△From left: Researcher Kyeungbin Kim, Dr. Boram Kim, Professor Yoon Kim, and Professor Dong-Wook Park of the University of Seoul