三维微纳智能器件的飞秒激光增减材直写技术研究

Femtosecond laser direct writing (fsLDW) was a non-contact, nanometer-resolution, optical fabrication technique in absence of mask or heat-affected zone, which was applicable in both additive and subtractive manufacturing. Owing to intrinsic advantages, fsLDW accelerated the functional integration and intelligentization of three-dimensional (3D) micron-nano devices. However, the existing researches proved that different ground-state particles required different photon energy for electronic transition process in transient photo chemical process, therefore, the non-resonant photon absorption effect of fsLDW often damaged chemical functional groups in decreasing the fabrication quality. Limited by regular materials and the optical modulation approaches, fsLDW only produced stationary structures with half wavelength resolution. To radically break the limitations, this project aimed for the basic mechanism underneath the photo-activated resonating two/multi photon polymerization or ablation process. Substantial accuracy improvement was achieved without losing the chemical functional groups. Herein, the fabricated devices featured with ultra-high spatial resolution, desirable surface quality, self-driven folding, actuating and sensing abilities. For this goal, we designed several new intelligent photocurable materials, technologically improved the close-looped 3D nano-precision positioning system, artificially moved laser focus three dimensionally in the shortest path for real one-sixth wavelength spatial resolution. We also planned to perform a series of behavior characterization, optimization and testing on the 3D micron-nano devices. This project was expected to satisfy the national strategic needs of nano-technology, which could fabricate much more complex 3D structure than conventional method, and developed the theoretical rationale of the optical fabrication, material science, photo-chemistry and interaction of ultrafast laser with matter, paving the way of wide application of the ultra-high resolution femtosecond laser fabrication.

飞秒激光直写是利用超快激光进行无掩膜、非接触、无热影响区、纳米精度的新一代光学制造技术，具备增减材复合加工能力，有利于三维微纳智能器件的一体化成形制造。现有研究中不同基态粒子电子跃迁能量和超快光化学过程差异大，导致非共振光子吸收加工质量低;受限于常规材料、光调制技术影响，常规激光直写只取得半波长精度且成形结构固定，无智能响应性。本课题旨在研究光子能量诱导智能材料的共振型双/多光子聚合/烧蚀机理，进而从根本上提高激光加工质量，并保留化学官能团赋予其组装、传感和执行等智能行为。为完成研究目标需研制多种温/水敏感智能材料；在技术上利用闭环三维精密定位系统和调制技术使空间精度提高至六分之一波长；开展一系列三维微纳智能器件的行为表征、优化和测试研究。本研究面向我国纳米科技的战略需求，有望拓宽光学制造、材料学、光化学、超快激光与物质相互作用等学科的基础理论，促进超高精度飞秒激光加工的应用。

传统“3D打印+树脂”和二维光刻工艺等无法满足纳米科技、微纳机电系统(M/NEMS) 、生物工程对复杂三维智能微纳器件的需求，而目前高分辨率双光子聚合制造技术因材料与机理瓶颈仍无法有效供应智能器件：可激光增材或减材制造的智能材料稀少；非共振吸收导致加工质量低；微纳尺度下的三维智能结构难以精确成形等。本项目成功的利用复合智能材料与先进飞秒激光增材减材技术，以相应性单体的可逆特性为契入点，遵循材料开发-激光制造-智能应用的技术路线，验证并明确基于共振吸收的智能响应性材料的飞秒激光增材与减材制造技术，在以下三个方面取得有创新性进展：1.揭示含光引发剂刺激响应性材料体系在激光诱导下的聚合反应和烧蚀效应，澄清材料系统对光能量的共振吸收关系。2.分析光脉冲重复频率、光波长、光斑形状等参数对加工质量的影响，结合时空光调制技术研发高精度、可调谐的激光直写微纳制造技术。3.设计和制备了多种微纳智能器件，通过有限元分析和实验表征微纳智能器件在环境刺激下的动态形变规律。本项目的实施有望为跨尺度、智能化、高精度三维微纳器件提供理论指导和相应的材料库，打破微纳尺度智能凝胶制备难，应用范围有限的现状，实现激光制造与智能响应材料的同步创新。