Physicochemical Soft Matter Research Team

Principal Investigator

PI Name
Fumito Araoka
Degree
Ph.D
Title
Team Director
Brief Resume
2003 Ph.D. in Engineering, Tokyo Institute of Technology, Japan
2003 Postdoctoral Researcher, Catholic University of Leuven, Belgium
2005 Postdoctoral Researcher, The University of Tokyo
2006 Postdoctoral Researcher, Tokyo Institute of Technology
2007 Assistant Professor, Tokyo Institute of Technology
2013 Unit Leader, Physicochemical Soft-Matter Research Unit, Cross-Divisional Materials Research Program, RIKEN Center for Emergent Matter Science
2018 Team Leader, Physicochemical Soft-Matter Research Team, RIKEN Center for Emergent Matter Science (-present)
Position name has been changed to Team Director as of April 1, 2025

Outline

Our team is mainly working on functionality of soft-matter systems from the viewpoints of physical experiments and analyses. In our research unit, particular attention is paid to liquid crystals due to their self-organizability leading to multifarious structures in which many interesting physical phenomena emerge. Our interest also covers potential applications of such soft-matter systems towards optical/electronic or chemical devices. For example, 1. Ferroelectric interactions and switching mechanisms in novel liquid crystalline ferroelectric materials, 2. Chirality related phenomena - origin and control of emergence, as well as applications of superstructure chirality in self-organized soft-matter systems, 3. Novel optical/electronic devices based on self-organized soft-matter systems.

Research Fields

Physical and Structural Properties of Functional Organic Materials

Keywords

Liquid crystals
Polymeric materials
Soft-matter physics
Optical properties
Organic nonlinear optics
Organic ferroelectrics

Results

Electric-Field Driven Ferroelectric Micro-Droplets

The recently-found ferroelectric nematics have been attracting much attention due to its proper ferroelectricity with highly fluidic nature. This state is enthusiastically investigated for its possibility towards epoch-making applications, as well as for fundamental science issues beneath the emergence of unprecedented physical properties, such as large apparent permittivity. Our group recently found a complex dynamic behavior, in which ferroelectric nematic microdroplets were transformed and dynamically driven by an ac electric field and crawled like some kind of micro creatures. This non-equilibrium phenomenon is resulted from the competition of electrostrictive and piezoelectric effects, and hence the shapes and dynamics of the droplets transit among various states, depending on the field conditions (amplitude, frequency, etc.). Interestingly, these dynamic droplets sometime move collectively like a swarm and thus possess active matter nature. Each individual droplet is considered as a micro-robot, thus named “Febot”.

“Febots” in collective motion, and their traces visualized by the motion capturing.

Topology-dependent Lehmann rotation in chiral nematic emulsions

Lehmann rotation is a ‘heat flow’-to-‘motion’ energy conversion effect in liquid crystals, which was found in the end of the 19th century. In spite of the huge effort by physicists for more than 100 years, its physical mechanism has not been clear yet. On the other hand, topology is ubiquitous in liquid crystals which can be treated as continua to understand many other complex physical systems. In this research, it was proven that highly efficient Lehmann rotation is realizable even in emulsion states of a chiral liquid crystal dispersed in a fluorinated oligomer, in which topological diversity is confirmed depending on the droplet size and the strength of chirality. Interestingly, the estimated heat-rotation conversion rate therein significantly depends on these inner topological states of the droplets. This result is not merely important as a key to solve the long-persistent physical problem in Lehmann rotation, but also interesting for fundamental sciences related to topology.

(A) Topological diversity in a chiral nematic emulsion, (B) Lehmann rotation depending on the topological states.

Members

Fumito Araoka

Team Director fumito.araoka[at]riken.jp

Hiroya Nishikawa

Research Scientist

Dennis Kwaria

Postdoctoral Researcher

Keita Saito

JSPS PD Researcher

Publications

  1. M. T. Mathe, H. Nishikawa, F. Araoka, A. Jakli and P. Salamon

    Electrically activated ferroelectric nematic microrobots

    Nat. Commun. 15, 6928 (2024)
  2. D. Okada, and F. Araoka

    Magneto-chiral Nonlinear Optical Effect with Large Anisotropic Response in Two-Dimensional Halide Perovskite

    Angew. Chem. Int. Ed. 63, e202402081 (2024)
  3. H. Nishikawa, K. Sano and F. Araoka
    Anisotropic fluid with phototunable dielectric permittivity
    Nat. Commun. 13, 1142 (2022)
  4. H. Nishikawa and F. Araoka

    A New Class of Chiral Nematic Phase with Helical Polar Order

    Adv. Mater. 33, 2101305 (2021)
  5. S. Aya, and F. Araoka

    Kinetics of motile solitons in nematic liquid crystals

    Nat. Commun. 11, 3248 (2020)

Articles

Contact Us

#117-2 Frontier Material Research Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan

E-mail:
fumito.araoka[at]riken.jp

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