Department of Mechanical & Aerospace Engineering, North Carolina State University, 911 Oval Drive, Campus Box 7910, Raleigh, North Carolina 27695, USA.
ACS Nano. 2011 Sep 27;5(9):7404-10. doi: 10.1021/nn202343w. Epub 2011 Aug 16.
This paper reports the first direct measurements of static friction force and interfacial shear strength between silicon (Si) nanowires (NWs) and poly(dimethylsiloxane) (PDMS). A micromanipulator is used to manipulate and deform the NWs under a high-magnification optical microscope in real time. The static friction force is measured based on "the most-bent state" of the NWs. The static friction and interface shear strength are found to depend on the ultraviolet/ozone (UVO) treatment of PDMS. The shear strength starts at 0.30 MPa without UVO treatment, increases rapidly up to 10.57 MPa at 60 min of treatment and decreases for longer treatment. Water contact angle measurements suggest that the UVO-induced hydrophobic-to-hydrophilic conversion of PDMS surface is responsible for the increase in the static friction, while the hydrophobic recovery effect contributes to the decrease. The static friction between NWs and PDMS is of critical relevance to many device applications of NWs including NW-based flexible/stretchable electronics, NW assembly and nanocomposites (e.g., supercapacitors). Our results will enable quantitative interface design and control for such applications.
本文报道了硅（Si）纳米线（NWs）与聚二甲基硅氧烷（PDMS）之间的静摩擦力和界面剪切强度的首次直接测量。使用微操纵器在高倍光学显微镜下实时操纵和变形 NWs。静摩擦力是基于 NWs 的“最弯曲状态”来测量的。发现静摩擦力和界面剪切强度取决于 PDMS 的紫外线/臭氧（UVO）处理。未经 UVO 处理时，剪切强度从 0.30 MPa 开始，处理 60 分钟时迅速增加到 10.57 MPa，处理时间更长时则下降。水接触角测量表明，PDMS 表面的 UVO 诱导疏水性到亲水性转换是导致静摩擦力增加的原因，而疏水性恢复效应则是导致其下降的原因。NWs 与 PDMS 之间的静摩擦力与 NWs 的许多器件应用密切相关，包括基于 NW 的柔性/可拉伸电子产品、NW 组装和纳米复合材料（例如超级电容器）。我们的研究结果将为这些应用的定量界面设计和控制提供依据。
