Zubritskaya Irina, Martella Daniele, Nocentini Sara
Nanofabrication Laboratory (NFL), Department of Microtechnology and Nanoscience -MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
ACS Appl Mater Interfaces. 2025 Feb 19;17(7):11100-11107. doi: 10.1021/acsami.4c20865. Epub 2025 Feb 4.
Materials that can visually report changes in the surrounding environments are essential for future portable sensors that monitor temperature and detect hazardous chemicals. Ideal responsive materials for optical sensors are defined by a rapid response and readout, high selectivity, the ability to operate at room temperature, and simple microfabrication. However, because of the lack of viable materials and approaches, compact, passive, and multipurpose practical devices are still beyond reach. To address this challenge, we develop a methodology to fabricate colored and responsive micropixels printed by digital light projection lithography on gold substrates. These structures are made by polymeric Liquid Crystalline Networks (LCNs) whose birefringence and external stimuli responsiveness allow for micrometric devices with visual and fast response that we here apply to a few applications. First, we show how varying the projected geometrical shape can become an effective tool to engineer symmetric disclination lines in the liquid crystal order. Depending on the thickness of the micropixels, LCNs give rise to a birefringence color under polarized light or a structural color under white light due to thin-film interference. By exposing the micropatterns to temperature variation and solvents, we demonstrate a real-time optical temperature detection and differentiation between selected organic chemicals. The proposed materials and fabrication method could be scaled up and extended to roll-to-roll printing, enabling future real-life applications of liquid crystalline polymers in affordable microdevices and optical sensors with a net advantage with respect to traditional lithographic techniques in terms of fabrication speeds and costs.
对于未来监测温度和检测有害化学物质的便携式传感器而言，能够直观报告周围环境变化的材料至关重要。光学传感器的理想响应材料具有快速响应和读出、高选择性、在室温下运行的能力以及简单的微加工等特点。然而，由于缺乏可行的材料和方法，紧凑、无源且多功能的实用设备仍然遥不可及。为应对这一挑战，我们开发了一种通过数字光投影光刻在金基板上制造彩色且响应性微像素的方法。这些结构由聚合物液晶网络（LCNs）制成，其双折射和外部刺激响应性使得微米级设备具有视觉和快速响应能力，我们在此将其应用于一些应用中。首先，我们展示了改变投影几何形状如何成为在液晶序中设计对称向错线的有效工具。根据微像素的厚度，LCNs在偏振光下产生双折射颜色，或在白光下由于薄膜干涉产生结构颜色。通过将微图案暴露于温度变化和溶剂中，我们展示了实时光学温度检测以及对选定有机化学品的区分。所提出的材料和制造方法可以扩大规模并扩展到卷对卷印刷，从而使液晶聚合物在经济实惠的微器件和光学传感器中实现未来的实际应用，在制造速度和成本方面相对于传统光刻技术具有明显优势。
