Akai Lab.

Neurons are organic materials that can grow. In the brain, neurons grow and wire each other in three dimensions, repeatedly destroying and repairing themselves. Ions transmit information within this neural network.
In our laboratory, we successfully created neural networks using conductive polymers that grew in a dendritic pattern, like neurons, using a machine learning method.
These conductive polymers increase the conductance between electrodes by increasing the number of wires and their thickness. Even when only one wire has an asymmetric thickness, the conductance can be varied by doping or dedoping by changing the electric potential at one terminal.
The functions of the polymer wire enable its use as a two-terminal memristive device with both long- and short-term memories.
Organic polymers grow directionally and have spatial degrees of freedom that inorganic materials do not. Hence, organic polymers may be the only materials with the potential to artificially construct a three-dimensional complex network of the brain based on a well-designed structure.
We aim to construct a mechanism capable of expressing information-processing functions that are similar to those of the brain by enabling free-wiring technology in a 3D space.

• 赤井 恵, 浅井 哲也, 中嶋 浩平, "学習する有機材料：リザバー計算に向けたニューラルネットワーク形成," 応用物理, vol. 90, no. 8, pp. 504-508 (2021).
• Hagiwara N. et al.,"Long- and short-term conductance control of artificial polymer wire synapses," Polymers, vol. 13, no. 2, pp. 312(1)-(10) (2021).
• Akai-Kasaya M. et al., "Evolving conductive polymer neural networks on wetware,"Japanese Journal of Applied Physics, vol. 59, no. 5, pp. 060601(1)-(9) (2020).