Spatiotemporal control of dynamic wetting on heterogeneous composite surfaces

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14490
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26030:Composite materials and interfaces-related
• Research Institution: The University of Tokyo
• Principal Investigator: Lee Yaerim 東京大学, 大学院工学系研究科(工学部), 講師 (40850714)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 動的濡れ / 単分子膜 / 固-液接触線 / 接触角ヒステリシス / 滑水

Outline of Final Research Achievements

In this study, we explored the dynamic wetting phenomena on the surface of self-assembled monolayers composed of molecules with different lengths and wettabilities from the perspective of resistance and contact angle hysteresis at the contact line.
Evaluation of rapid wetting on PEG-silane monolayer surfaces with different repeat units of PEG chains revealed that a delay occurs on the surface of longer-chain PEG-silane monolayer surfaces. This represents a direct observation of the influence of molecular-scale behavior on macroscopic dynamic wetting and is a new discovery that challenges the conventional understanding that dynamic wetting of droplets on hydrophilic surfaces is inertial dominated. Furthermore, it was found that the longer-chain PEG molecules exhibit very low contact angle hysteresis, clarifying that energy dissipation due to molecular behavior, as observed in rapid wetting experiments, reduces the resistance to contact line movement from the equilibrium state.

Free Research Field

動的濡れ、表面界面制御

Academic Significance and Societal Importance of the Research Achievements

液滴が固体表面上で濡れ拡がる現象は身近でありながら、印刷や塗装、熱交換器など様々な産業分野において重要である。濡れを理解する基礎系であるキャピラリー濡れの中でもっとも非平衡性の高い初期の高速濡れは、これまで主に慣性、粘性、接触線摩擦間のバランスとして議論され、水のような低粘性流体の場合は慣性支配であり濡れ拡がりの時間のべき乗数は表面の濡れ性、つまり静的接触角に応じて決まると理解されてきた。本研究の成果により濡れにおける分子スケールの効果が明らかになり、実用応用で重要となる接触角ヒステリシスの理解でも同様の視点が必要でることが確認されたことから、今後濡れ分野の学理のさらなる深化が期待できる。