屈曲引导的微尺度三维结构组装方法的力学模型、设计概念与实验研究

Three-dimensional (3D) micro/nanostructures have important widespread applications in a broad range of areas, such as biomedical devices, microelectromechanical systems and etc. They have been the research focus of many technological fields. The existing fabrication/assembly approaches of 3D micro/nanostructures are however, constrained by a narrow range of applicable materials and 3D geometries. Especially, there is a lack of approaches capable of building complex 3D structures of high-performance semiconductor materials. The buckling-guided assembly approach of 3D microstructures, as developed by the applicant in the previous works, can overcome the above limitation effectively. However, the development of this assembly approach is still at the beginning stage, and many aspects, such as the finite-deformation theory of postbuckling and the designs concepts, are still far from mature. This project will (1) establish the finite-deformation theoretical model of postbuckling in ribbon-type films with complex curved patterns, and develop the computational mechanics model of the buckling-guided assembly process for the film/substrate system, with the consideration of the interface; (2) propose a design concept of residual stresses for the 3D microstructures formed through buckling, to avoid multiple buckling modes that have similar levels of energy, and experimentally fabricate the complex microstructures with multi-level 3D configurations; (3) construct the model and algorithm of inverse problem for the buckling-guided assembly approach, such that the initial 2D designs required to transform into the prescribed target 3D structures can be obtained rapidly. The results of this research project will provide important theoretical foundation and experimental basis for the assembly approach of 3D microstructures guided by buckling.

三维微纳米结构在生物医学器件、微机电系统等众多科技领域具有重要而广泛的应用，一直以来都是科技研究的焦点。然而现有的三维微纳米结构制备及组装方法却较为局限，尤其是缺乏高性能半导体材料的复杂三维结构成型方法。申请人在先期工作中建立的屈曲引导的微尺度三维结构组装方法，可有效解决这一局限。然而这种组装方法的发展尚处于起步阶段，在后屈曲大变形理论、设计概念等方面都还不成熟。本项目拟（1）建立复杂曲线构型的条带状薄膜的后屈曲大变形理论模型，并发展考虑界面影响的硬薄膜/软基底系统的屈曲组装过程的计算力学模型；（2）提出三维屈曲微结构的残余应力设计概念，避免出现多种能量相近的屈曲模态，实验制备出具有复杂多层次三维构型的微尺度结构；（3）构建屈曲组装方法的反问题模型和算法，从而针对给定的目标三维结构，快速地得到所需的初始二维设计。本项目的研究成果将为屈曲引导的三维微结构组装方法提供重要的理论基础及实验依据。

三维微纳结构在生物医学器件、超材料和微机电系统等领域具有重要的应用，可控的三维微纳米结构成型方法一直是研究的焦点。然而，现有的三维微纳米结构制备及组装方法在结构形式、成型速度、材料选择等方面仍存在一定局限性，特别在成型复杂三维拓扑时应用高性能半导体材料的上存在较大困难。申请人在先期工作中建立的屈曲引导的微尺度三维结构组装方法可有效突破这一瓶颈。为了进一步发展这种组装方法，使其具备更广泛的应用场景，本项目首先建立了相应的理论模型，包括基于能量法和摄动法的二维条带状薄膜三维后屈曲大变形理论模型，和针对硬薄膜/软基底系统中弱界面未脱粘阶段中界面影响的计算力学模型。进一步地，为了更有效地调控三维屈曲微结构的构型，本项目提出了在结构中施加残余应力的设计概念，并发展了基于氮化硅的材料体系。此外，为了快速得到目标三维结构的初始二维设计，本项目建立了基于理论模型的逆向设计方法以及基于自适应遗传算法的反问题求解模型，并通过一系列结构实例验证了逆向设计方法的收敛性和准确性。最后，基于所发展的微尺度屈曲三维结构组装方法，本项目设计并制备了包括可重构天线，手性三维超材料和可视大量程应变传感器在内的一系列微尺度三维功能器件。本项目的研究成果将为以高性能半导体材料为基础的三维微结构组装方法和功能器件制备提供重要的理论基础及实验依据。