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Journal of Physics D: Applied Physics Volume 47 Number 36, 2014. Ryota Maruyama , Naoki Asakawa.
Faculty of Science and Technology, Gunma University, 1-5-1 Tenjincho, Kiryu, Gunma 376-8515, Japan.
Abstract
A design of a bio-inspired signal/information processing device and the fabrication of a stochastic delay-derivative element (SDDE) using an immiscible polymer binary mixture of poly(L-lactic acid) with poly(ε-caprolactone) are described. A functional aspect of bio-inspired signal/information processing using both analogue electric circuits and numerical simulations are shown. Nano-thin films of polymeric binary mixtures were explored to realize the SDDE.
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Additional Information
Prof. Naoki Asakawa’s group at Gunma University in Japan reports novel concept of bioinspired signal/information processing devices that have hierarchical instabilities and realization of the devices using polymer binary mixture. It is known that biological system adaptively operates based on a mechanism of attractor selection under unexpected environmental changes, with ultra-low energy consumption. Attractors are thought of as multistable properties toward which a system tends to evolve for various initial conditions of the system, and which have been found in almost several natural sciences and engineerings including electronics, photonics, mechanics, biology, etc. The attractors should be generated or annihilated depending on environmental changes, and the system undergoes noise-induced transitions between attractors in association with the environmental changes, to temporally settle down to an appropriate attractor. A mechanism of fluctuation-driven attractor selection is as origin of adaptability and robustness of biological systems.
For mimicking such biological information systems, two aspects of the system are important, one is generation/annihilation of attractors and the other is stochastic transitions between attractors associated with environmental changes. A mechanism of delayed feedback is highly related to the generation/annihilation, and noise is origin of quasi-stochastic transition between attractors.
To realize these applications, Asakawa and Ryota Maruyama, his PhD student, designed and fabricated such bioinspired signal/information processing device element, which is the stochastic delay-derivative element (SDDE) using the binary mixture of poly(L-lactic acid) [PLLA] and poly (e-caprolactone) [PCL]. The binary mixture is known as a typical immiscible semicrystalline polymer mixture. PCL is selected as a low-Tm material (about 60 °C) and PLLA is selected as a high-Tm one. To fabricate the SDDE using the immiscible polymer mixture, they focused on the two factors that could be important to characterize and control the stochastic behavior of the element:
phase separated structure of immiscible binary mixture and crystallization behavior.
Since the melting temperature of PCL is near room temperature, the PCL component was used to endow the delay-derivative element (DDE) with quasi-stochastic behavior; that is, a noise generator based on a stochastic capacitor(see Figure). As a result, they found that the SDDE using a PLLA:PCL binary mixture showed spatio-temporal fluctuations that depended on the fabrication conditions such as the fraction of PCL and successive cooling after the isothermal crystallization of PLLA.
This research opens up novel applications of materials with low-melting point.
