柔性微纳功能器件的可控变形及流动特性研究

The flexibility and deformability allow organisms in nature to adjust their surface topography and body shape in self-adaptive fashions into streamline which can effectively reduce the fluid resistance in the complex environment. The characteristics are of meaningful reference value for developing functionalized devices, especially in the microfluidic environment with relatively high resistance. In order to reveal the mechanism of drag reduction under different flow conditions with flexible surfaces and deformable structures at micro/nano scales, in this project we plan to prepare precursor solution of flexible hydrogel-based intelligent materials with environmental response and develop flexible functionalized micro/nano-devices with controllable deformation by the 4D printing based on 3D direct laser writing. First of all, theoretical analysis and in-situ mechanical testing will be carried out to learn constitutive relationship of stress-strain of printed hydrogel materials, and investigate the mechanism of how the gradient tensor divided into elastic deformation and the chemical swelling influences deformation behavior during swelling process. Secondly, based on numerical simulation with the finite element method and experimental test, the methodology for design and analysis of flexible functionalized micro/nano-structures with controllable deformation will be systematically established, and the response mechanism of the directional deformation of flexible functionalized micro/nano-devices under different external excitation is revealed. Finally, by measuring evolution of the surface topography and the boundary layer flow field, the intrinsic law and microcosmic mechanism of how structure, elasticity and wettability influence drag reduction are studied. The present project will provide strong theoretical guidance for swimming optimization of micro/nano-devices with flexible adaptive and active deformation control in complex microfluidic environments.

柔性及可变形特征允许生物体在复杂流体环境中自适应调节成流线型形貌及体态来减小行进阻力，对功能器件的研制特别在相对阻力更大的微流体环境下具有重要借鉴意义。为了揭示微纳尺度下柔性表面及可变形结构在不同流动状态下的减阻机理，本项目拟配制具有环境响应的柔性水凝胶基智能材料，并利用基于三维激光直写的4D微纳打印技术研发具有可控变形的柔性微纳功能器件。通过原位测试及理论分析，掌握所制水凝胶材料的应力应变本构关系，探索溶胀过程中弹性变形及化学溶胀张量对变形行为的影响机理。基于有限元模拟与实验测试，系统建立具有变形可控柔性微纳功能结构的设计及分析方法，揭示柔性微纳功能器件在不同外界激励下的定向形变响应机理。通过测量表面形貌演化和边界层流场，研究柔性微纳功能器件的构型、弹性特性、表面浸润性对其流动减阻影响的内在规律和微观机理，为最终实现具有柔性自适应且主动变形控制的微纳功能器件在微流体内的运动提供理论指导。

柔性及可变形特征允许生物体在复杂流体环境中自适应调节成流线型形貌及体态来减小行进阻力，对功能器件的研制特别在相对阻力更大的微流体环境下具有重要借鉴意义。在工程中，如何设计和制造具有主动变形的智能柔性微纳米功能器件来适应复杂微流体环境，并有效驱控使其完成多功能变体行为来实现运动及行为性能增强，是本项目研究的核心重点。本项目独立研发了可打印智能生物水凝胶材料，首次面向复合式可重构智能微机器的制造，提出了基于可调双光子聚合的四维激光直写技术; 通过对变体系统引入机械增益铰链，实现微小限制空间内的可控大变形; 跳出Origami折纸层叠设计局限，提出基于模块化设计的四维微纳打印设计方法; 实现了各类面向生物医疗应用的复杂功能变体结构；同时，本项目也探索在复杂流体环境下，微纳器件柔性变体的运动增强方式、驱控微流管道以及磁驱动实验平台的建造。在此基础上，针对目前的变体技术只能实现单一变形行为，首创通过纳米小磁体的可编辑特性实现对微纳米机器人的多变体行为的有效控制，该技术为下一代具有变形信息存贮和计算功能的智能微纳米机器人提供了有效方案。截止2020年12月31日，已发表SCI论文11篇，包括Nature、Materials Today、Science Advances、PNAS、Advanced Functional Materials等国际顶级期刊，其中，中科院分区一区8篇，影响因子总和（不完全统计）为156.812，Google Scholar引用250次；获得实用新型专利1项、发明专利2项。入选ESI高被引论文1篇，PNAS文章入选当期杂志封面，最佳海报奖1次，项目申请人已受邀主旨演讲6次，团队共出席8次国际学术会议。本项目的重要研究成果受到德国科学院院士Martin Wegener教授、美国加州大学Joseph Wang教授（皇家化学学会会士）、德国马普所Metin Sitti教授、美国麻省理工学院赵选贺教授等众多专家学者的广泛关注和高度评论。相关研究成果在苏黎世联邦理工学院和瑞士保罗谢勒国家实验室等机构网站进行头版封面报道，已获到包括Physics World、Science Daily、Phys.Org、中国科学报、科学网等30多家媒体的新闻报道，超过百家网站进行转载。