Flexible mesostructure technologies: from soft mechanical metamaterials to 3D flexible electronics
柔性微结构技术：从软质力学超材料到三维柔性电子器件
Yihui Zhang（张一慧）
ABSRACT
Complex 3D mesostructures in biology (e.g., cytoskeletal webs, neural circuits, and vasculature networks) form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, ranging from bio-integrated electronics, MEMS, to metamaterials and micro-robotics. However, the development of artificial 3D soft materials and electronics with complex 3D geometries and/or mechanical properties that reproduce those of biological tissues is extremely challenging. In this presentation, I will discuss a set of flexible mesostructure technologies for 3D architected materials and flexible electronics with customized geometries and mechanical properties. In the first part, I will introduce a class of bio-inspired network designs to enable the development of biomimetic materials that can reproduce accurately nonlinear mechanical properties of soft biological tissues, as well as soft mechanical metamaterials with exotic effective properties (e.g., negative swelling, thermally-induced shear, negative Poisson’s ratios, etc.) that do not exist in conventional materials. I will show a couple of examples to demonstrate the utility of these architected materials as important platforms of bio-integrated electronics. In the second part, I will introduce a class of mechanics-guided assembly approaches that exploit controlled, compressive buckling, for constructing complex 3D micro/nanostructures rapidly from patterned 2D micro/nanoscale precursors. The compatibility of these approaches with the state-of-the-art fabrication techniques in semiconductor industries, along with their versatile capabilities, provides enormous design options in the development of new functional 3D devices. I will introduce the enabling applications in 3D flexible electronic systems, including reconfigurable antennas and wearable health-monitoring systems.
生物体自然生长所形成的复杂三维细微观结构（如细胞骨架网、神经回路和脉管网络）在最基本的生命活动中发挥着关键作用。在人造的器件中构建类似的三维微结构同样在众多前沿领域有着重要的应用前景，涵盖生物集成电子器件、微机电系统、超材料和微型机器人等。然而，发展具有类似于生物组织的复杂三维几何构型和/或优异力学性能的人造三维软质材料和电子器件是极具挑战性的。在本次讲座中，将介绍一系列柔性微结构技术，用以发展可定制几何构型和力学性能的三维结构材料和三维柔性电子器件。第一部分将介绍一类仿生网状软材料的设计方法，该方法既可用于实现能够精确再现生物软组织非线性力学行为的仿生材料，又可用于构建具有传统材料所无法实现的特殊性能（如负溶胀、热致剪切、负泊松比等）的软质力学超材料。报告中将展示多个典型的例子来说明这些结构化材料为生物集成电子器件的发展和应用提供了一个重要平台。第二部分将介绍一系列基于可控压缩屈曲变形的力学引导的三维组装方法，其适用于将图案化的二维微纳米级前驱体快速组装为复杂的三维微/纳米结构。这些方法与成熟的半导体制备工艺相兼容，并且具备独特的设计制备灵活性，为发展新型三维功能器件提供了大量的可设计选项。此外，将介绍基于该方法实现的一些三维柔性电子系统，包括可重构天线和可穿戴健康监测系统。
BIOGRAPHY
Yihui Zhang is a Professor of Engineering Mechanics at Tsinghua University. His group (http://yihuizhang.org/) is dedicated to addressing the grand challenges in the frontiers of science and technologies through creative uses of mechanics principles and cross-fertilization among diverse disciplines, which drives the development of new mechanics theories and computational models of advanced materials and structures, as well as novel designs and fabrication approaches of materials and systems with unprecedented properties. A major focus of Dr. Zhang’s current research is the study of flexible mesostructure technologies for the development of soft architected materials that can reproduce and/or exceed the mechanical/physical properties of soft biological tissues, as well as 3D microelectronics that can offer new functionalities and/or enhanced performances.
Dr. Zhang’s is the recipient of several honors and awards, including, MIT Technology Review's 35 Innovators Under 35 (MIT TR35), ASME Thomas J.R. Hughes Young Investigator Award, Society of Engineering Science’s Young Investigator Medal, ASME Sia Nemat-Nasser Early Career Award, Eshelby Mechanics Award for Young Faculty, ASME Melville Medal, NSFC Excellent Youth Funding, and Qiu Shi Outstanding Young Scholar Award. He is an associate editor of Mechanics of Materials, Research and ASME-Journal of Applied Mechanics, and serves on the editorial board of several academic journals.
张一慧，清华大学工程力学系教授。他的课题组（http://yihuizhang.org/）致力于利用力学原理和多学科交叉解决世界科技前沿领域中的挑战性科学问题，在此过程中建立先进材料和结构的新力学理论和计算模型, 并发展具有特异性能的材料和系统的设计及制造方法。张博士课题组当前的主要研究焦点是柔性微结构技术，致力于发展能够重现或超越生物软组织力学/物理性能的软质结构材料，以及能够提供新功能或高性能的三维微电子器件。
张博士曾获麻省理工学院技术评论“全球35位35岁以下创新者”、美国机械工程师协会Thomas J.R. Hughes青年学者奖、国际工程科学协会青年学者奖章、美国机械工程师协会Sia Nemat-Nasser早期职业生涯奖、美国机械工程师协会Melville奖章、Eshelby青年力学教授奖、国家自然科学基金委优青、香港求是科技基金会“求是杰出青年学者奖”等荣誉。目前担任《Mechanics of Materials》、《Research》和《ASME-Journal of Applied Mechanics》的Associate Editor，以及多个学术刊物的编委。