相比于传统硬质无机电子器件，无机柔性电子器件通过结构的优化设计降低无机电子材料应变的同时实现了较高水平的拉伸性。本文通过理论分析、实验以及有限元计算相结合的方法，基于弹塑性力学理论提出可拉伸互联结构设计与制备的新策略；并建立相应的力学模型，揭示其变形机理；基于力学结构设计提出一种高性能应变传感器设计的新方案。沿着以上研究思路，本文取得以下的创新性成果：

1）提出了一种提高柔性电子器件弹性延展性的新策略——过加载策略。其基本原理在于过加载过程中由于弹塑性本构关系的演变，使得可拉伸互联结构关键部位的弹性范围扩大了一倍。理论、有限元以及实验结果表明过加载策略可以使柔性电子器件的弹性延展性提高一倍，并且该策略对不同几何构型的互联结构同样有效。

2）建立了一种金属层韧性失效的力学模型，定量研究了有机/无机复合结构中聚合物基底对无机金属层拉伸失效的影响。对于有机/无机双层复合结构，金属层的拉伸断裂应变随着有机/无机层厚度比和金属层的宽厚比的增加而增大，最后趋于饱和。相同聚合物厚度的情况下，有机/无机/有机三层结构对金属层应变局部化的抑制效果优于有机/无机双层结构。此外，共形的聚合物基底能够降低非屈曲蛇形互联结构的塑性变形。

3）提出了一种具有确定性接触关系的编织可拉伸应变传感器。传感器中的涤纶纤维将乳胶丝基底与银纤维紧紧捆绑在一起，形成周期性的“Y”形编织结构，以避免纤维之间的相互滑移，使银纤维之间在循环拉伸过程中具有确定的接触与分离关系，从而使该应变传感器具有重复性好（重复性误差为3.74%）、灵敏度高（灵敏度系数可以高达140）、传感范围广（50%）和鲁棒性优异等优点。针对该应变传感器，建立了力-电耦合模型，定量地刻画了其传感机理。

4）通过混合编织工艺制备了一种高拉伸性（>50%）、高导电性(2.8 Ω/m)的可拉伸外部互联导线。该编织可拉伸导线通过机织工艺将普通织物纤维、导线和乳胶丝混合编织而成。得益于这种混合编织结构，该编织导线在一定应变范围内（80%）具有较小的拉伸刚度，使其不影响智能穿戴设备的舒适性，在极端载荷下织物纤维承担主要的外载，可避免导线结构受到破坏。针对该编织可拉伸导线结构，建立了相应的力学模型，揭示了其变形机理。

Compared with conventional rigid inorganic electronics, inorganic flexible electronic devices achieve a higher level of stretchability while decreasing the strain on inorganic electronic materials through optimal structural designs. In order to improve the stretchability of flexible electronics, this paper proposes a new strategy for the design and preparation of stretchable interconnects based on the theory of elastoplastic mechanics through a combination of theoretical analysis, experiments, and finite element calculations. An effective mechanical model is established to reveal its deformation mechanism. A new scheme of high-performance strain sensor based on mechanical structure design is proposed. Along the above research line, following innovative results are obtained in this paper:

1) A new strategy to improve the elastic stretchability of flexible electronics is proposed, i.e., overstretch strategy. The underlying mechanism is that the elastic range of the critical part of the stretchable structure is doubled, owing to the evolution of the elastoplastic constitutive relation during overstretching. The theoretical, numerical, and experimental results collectively prove that the overstretch strategy can double the designed elastic stretchability of stretchable electronics and is valid for various geometrical interconnects.

2) A mechanical model for the ductile failure of metal layers is established, and the effect of polymer substrate on the tensile failure of inorganic metal layers in organic/inorganic composite structures is quantitatively investigated. For the organic/inorganic bilayer composite structure, the tensile fracture strain of the metal layer increases with the increase of the thickness ratio of the organic/inorganic layer and the width-thickness ratio of the metal layer, and finally tends to saturate. For the same polymer thickness, the organic/inorganic/organic triple-layer structure suppresses the strain localization in the metal layer better than the organic/inorganic double-layer structure. In addition, the conformal polymer substrate can lower the plastic deformation of non-buckling serpentine interconnects.

3) A braided stretchable strain sensor with deterministic contact relations is proposed. The polyester fibers in the sensor bind the latex yarns substrate tightly to the silver fibers, forming a periodic "Y" shaped structure to avoid mutual slippage between the fibers and to provide a deterministic contact and separation relationship between the silver fibers during the cyclic stretching, thus providing the strain sensor with high repeatability (repeatability error is 3.74%), high sensitivity (sensitivity factor can be as high as 140), wide sensing range (50%), and excellent robustness. For this strain sensor, a force-electric coupling model is developed to quantitatively characterize its sensing mechanism.

4) Stretchable external interconnects with high stretchability (>50%) and high conductivity (2.8 Ω/m) are fabricated by a hybrid braiding process. The braided stretchable interconnect is made by braiding a mixture of common fabric fibers, wires and latex yarns. Due to this hybrid braided structure, the braided interconnect has a small tensile stiffness within a certain strain range (80%), so that it does not affect the comfort of the smart wearer, while the fabric fibers take the main external load under extreme load, thus avoiding damage to the interconnects. For the braided stretchable interconnect, this paper establishes the corresponding mechanical model to reveal its deformation mechanism.