This paper investigates the physical process of polymer nanostructure deposition from a heated atomic force microscope (AFM) tip and focuses on the role of capillary-driven flow on deposited feature sizes during thermal dip-pen nanolithography. We used a heated AFM tip to deposit 50–350 nm wide poly(methyl methacrylate) nanoribbons by varying tip temperature, tip speed, and polymer molecular weight. For polymers of different molecular weights, the width of the deposited polymer nanoribbons decreases with capillary number (Ca), independent of tip temperature, tip speed, and polymer molecular weight. These results indicate that the capillary-driven flow governs polymer nanostructure deposition from a heated tip. For high molecular weight polymers deposited with feature size close to the polymer radius of gyration R_g, the molecular weight also influences the size of the deposited polymer ribbon. Using scaling arguments, we show that the feature size can be predicted by Ca and R_g. Uniform and continuous deposition occurs only when Ca << 1, confirming that the polymer flow is driven by the capillary force. The results of this study enable better control of speed and resolution at which polymer nanostructures can be fabricated using AFM.

中文翻译：

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纳米级毛细管驱动的流量和分子量控制着从加热尖端沉积的聚合物纳米结构

本文研究了从热原子力显微镜（AFM）尖端沉积聚合物纳米结构的物理过程，并着重探讨了在热浸笔式纳米光刻过程中毛细管驱动的流量对沉积特征尺寸的作用。我们使用加热的AFM尖端，通过改变尖端温度，尖端速度和聚合物分子量来沉积50-350 nm宽的聚（甲基丙烯酸甲酯）纳米带。对于不同分子量的聚合物，沉积的聚合物纳米带的宽度随毛细管数而减小（Ca），而不受尖端温度，尖端速度和聚合物分子量的影响。这些结果表明，毛细管驱动的流动控制着从加热尖端沉积的聚合物纳米结构。对于沉积的特征尺寸接近聚合物回转半径R _g的高分子量聚合物，分子量也影响沉积的聚合物带的尺寸。使用缩放参数，我们表明可以通过Ca和R _g预测特征尺寸。仅当Ca发生均匀且连续的沉积 << 1，确认聚合物流是由毛细管力驱动的。这项研究的结果可以更好地控制速度和分辨率，使用AFM可以制造聚合物纳米结构。