Elucidating nonlinear dynamics of nanometer-scale fluids with microscopic experimental study

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05064
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thin film/Surface and interfacial physical properties
• Research Institution: Osaka Electro-Communication University
• Principal Investigator: Kageshima Masami 大阪電気通信大学, 工学部, 教授 (90251355)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 非線形性 / 原子間力顕微鏡 / 生体適合性高分子 / 粘弾性 / シア / 臨界状態 / 相分離

Outline of Final Research Achievements

Nonlinear behavior of nano-confined fluid was experimentally analyzed from a microscopic viewpoint. Atomic force microscopy (AFM) specially tuned for shear viscoelasticity analysis was utilized. Bio-compatible polymer MPC noted for its characteristic lubricity in a hydrated state was constrained between two hydrophilic surfaces to analyze its shear viscoelasticity while the shear amplitude was swept from nanometer to subnanometer level. It was found that the viscous property was classified into drastically contrasting regimes depending on the amplitude range. This remarkable behavior was interpreted from the roles played by polymers and water molecules during the sliding motion. In addition, characteristic complex mechanical interaction between two surfaces placed in near-critical binary mixture was detected using the similar viscoelasticity analysis technique based on AFM.

Free Research Field

表面・界面物理、ソフトマター物理

Academic Significance and Societal Importance of the Research Achievements

人工関節などの潤滑剤としての応用が期待される生体適合性高分子の水和状態でのシア特性を計測し、水と高分子が複雑に表面と作用して、非線形性に結びつく特徴的な摩擦・潤滑特性を生じることを実験的に示した。これによって、非線形性の起源について分子レベルの洞察を与えることができるとともに、応用上重要な狭い空間内の流体の摩擦・潤滑特性が、バルク流体のそれとは異なる特徴的なものであることを示した。また、臨界２成分系中での複素力学応答計測では、臨界カシミール効果や粘性異常等の興味深い現象について、前例の少ないナノメーターレベルの実験データを提供し、相転移・臨界現象の物理の最先端に貢献する可能性を示した。