We demonstrate the use of tip-enhanced Raman spectroscopy (TERS) on polymeric microstructures fabricated by two-photon polymerization direct laser writing (TPP-DLW). Compared to the signal intensity obtained in confocal Raman microscopy, a linear enhancement of almost two times is measured when using TERS. Because the probing volume is much smaller in TERS than in confocal Raman microscopy, the effective signal enhancement is estimated to be ca. 10⁴. We obtain chemical maps of TPP microstructures using TERS with relatively short acquisition times and with high spatial resolution as defined by the metallic tip apex radius of curvature. We take advantage of this high resolution to study the homogeneity of the polymer network in TPP microstructures printed in an acrylic-based resin. We find that the polymer degree of conversion varies by about 30% within a distance of only 100 nm. The combination of high resolution topographical and chemical data delivered by TERS provides an effective analytical tool for studying TPP-DLW materials in a non-destructive way.

我们演示了尖端增强拉曼光谱（TERS）在通过双光子聚合直接激光写入（TPP-DLW）制造的聚合物微结构上的使用。与共焦拉曼显微镜获得的信号强度相比，使用TERS时可测量到几乎两倍的线性增强。因为在TERS中探测体积比在共聚焦拉曼显微镜中小得多，所以估计有效信号增强约为1。10 ⁴。我们使用TERS获得具有相对较短的采集时间并具有由金属尖端顶点曲率半径定义的高空间分辨率的TPP微观结构的化学图。我们利用这种高分辨率来研究丙烯酸基树脂印刷的TPP微观结构中聚合物网络的均匀性。我们发现，聚合物的转化度在仅100 nm的距离内变化约30％。TERS提供的高分辨率地形和化学数据的结合为以无损方式研究TPP-DLW材料提供了有效的分析工具。