2025.11.18《Electrically Tunable Friction: From Sticky to Slippery with Ionic Hydrogels》

在《Advanced Materials》发表的研究中，研究者针对宏观尺度下摩擦力难以实现实时、可逆且大幅调控这一长期挑战，从界面分子间作用力调制的角度出发，提出了一种基于电场协同调控静电力与氢键力的新策略，实现了摩擦系数跨数量级的精准可控。该工作首次在无外加液体润滑条件下，实现了离子水凝胶摩擦系数从传统干摩擦状态（COF≈1–2）到超低摩擦状态（COF≈0.03）的超过50倍可逆调节。研究采用以聚乙烯醇（PVA）为骨架、掺杂LiTFSI的离子凝胶体系，在外加电场作用下驱动Li⁺/TFSI⁻在凝胶—金属界面的定向迁移，重构界面电荷分布并调制PVA链间氢键强度，从而实现摩擦行为的原位调控。进一步研究揭示，电场诱导的电渗析效应是实现摩擦调控的关键机理：负电压下，TFSI⁻阴离子在界面富集，显著削弱静电力和PVA氢键，形成若界面粘附和易滑移凝胶界面，大幅降低界面摩擦阻力；而在正电压或无电场条件下，界面以强粘附和固–固接触为主，表现出高摩擦特征。由此，该工作建立了通过电场精细调控界面分子间作用力状态，进而精准调节宏观摩擦性能的全新路径，为宏观电控摩擦、智能表面及自适应机器人系统提供了新的理论框架与材料设计范式。

该文的第一作者为：刘宸旭，通讯作者为：曾宏波教授。

In the research published in Advanced Materials, researchers addressed the long-standing challenge of achieving real-time, reversible, and substantial control over friction forces at the macroscale. From the perspective of intermolecular force modulation at the interface, they proposed a novel strategy based on electric field-assisted regulation of electrostatic and hydrogen bonding forces, enabling precise and controllable friction coefficients across multiple orders of magnitude. This work achieved reversible adjustment of the friction coefficient of ionic hydrogels from a traditional dry friction state (COF ≈ 1–2) to an ultra-low friction state (COF ≈ 0.03), representing a more than 50-fold change, without the addition of external liquid lubrication for the first time. The study employed an ionic gel system with polyvinyl alcohol (PVA) as the backbone and doped with LiTFSI. Under the influence of an external electric field, the directed migration of Li⁺/TFSI⁻ at the gel-metal interface was driven, reconstructing the interfacial charge distribution and modulating the hydrogen bonding strength between PVA chains, thus achieving in-situ regulation of frictional behavior. Further research revealed that the electric field-induced electrodialysis effect is the key mechanism for achieving friction regulation: under negative voltage, TFSI⁻ anions accumulate at the interface, significantly weakening electrostatic forces and PVA hydrogen bonding, forming a gel interface with reduced interfacial adhesion and increased slipperiness, thereby greatly reducing interfacial frictional resistance; whereas under positive voltage or in the absence of an electric field, the interface predominantly exhibits strong adhesion and solid-solid contact, displaying high friction characteristics. Thus, this work established a novel pathway for precisely adjusting macroscopic friction performance by finely regulating the state of intermolecular forces at the interface through electric fields, providing a new theoretical framework and material design paradigm for macroscopic electrically controlled friction, smart surfaces, and adaptive robotic systems.

First author: Chenxu Liu

Corresponding author: Professor Hongbo Zeng

Electrically Tunable Friction: From Sticky to Slippery with Ionic Hydrogels