基于形状记忆聚合物的高效转印方法

In recent years, stretchable and flexible inorganic electronics attracts more and more interest in the field of biomedicine. During fabrications of the stretchable and flexible inorganic electronics, transfer printing is a key step that transfers the device from the rigid growth substrate to the soft target substrate. However, current transfer printing methods based on mechanical design are difficult to achieve the quantitative control due to their intrinsic dependence on the loading rate. Therefore, it is very necessary to develop a precise, controllable and highly efficient transfer printing method. In this project, we present a temperature-controlled transfer printing method based on the shape memory effect of shape memory polymers (SMP). The main idea is that, under the external pressure the large contact area between micro-patterns of SMP and inorganic films guarantees the pick-up process below the glass transition temperature Tg, while the printing process is achieved above Tg by the extremely small contact area automatically resumed due to shape memory effect of SMP. Under experimental environments, we are able to quantitatively control the key material and geometrical parameters of SMP. Based on the finite deformation theory, an adhesive contact model between micro-patterns of SMP and inorganic films is established for the sake of optimization criterions to the SMP-stamp design for material and geometrical parameters. This project provides scientific basis and technical guidelines for precise, controllable and highly efficient transfer printing techniques.

近年来，可延展柔性无机电子在生物医学领域倍受关注。可延展柔性无机电子制备的关键环节是转印，即将电子器件从刚性生长衬底转移到柔性承印衬底。然而，现有的基于力学设计的转印方法过度依赖外加载荷速率，不便于定量化操控。因此，有必要发展一种精准、高效、可控的转印方法。本项目基于形状记忆聚合物材料（SMP）的形状记忆效应提出一种温度控制的转印方法，其原理是：在玻璃化转变温度Tg以下实现SMP微结构与无机薄膜的大面积黏附接触以完成剥离过程；然后控制温度至Tg以上，SMP微结构自动恢复初始形状使得黏附接触面积骤减以完成印制过程。本项目通过精确可控的实验手段实现转印过程中关键材料和几何参数的定量化控制，结合实验、理论和数值方法建立基于有限变形的SMP微结构黏附接触模型，并建立大规模转印成功率的优化准则，为实现精准、高效、可控转印提供科学依据和技术指导。

近年来，可延展柔性无机电子在生物医学领域倍受关注。可延展柔性无机电子制备的关键环节是转印，即将电子器件从刚性生长衬底转移到柔性承印衬底。然而，现有的基于力学设计的转印方法过度依赖外加载荷速率，不便于定量化操控。因此，有必要发展一种精准、高效、可控的转印方法。本项目提出了一种基于形状记忆聚合物（Shape Memory Polymer, SMP）的转印方法，该方法受到激光直写技术的启发，具有高度可控、空间可选择的界面粘附调控能力，为实现精准、高效、可控转印提供科学依据和技术指导。本项目首先选取了具有良好的形状记忆效应、低橡胶态模量和高失效应变的SMP。然后，在该SMP表面制备出类四棱锥微结构并对其进行变形和界面粘附测试，结果表明通过控制SMP印章微结构的构型可以实现很大的界面粘附调控范围。接下来，高效率地将不同形状、不同厚度的硅薄膜转印到了柔性衬底，并进一步实现了更为复杂的光电薄膜混合转印。最后，通过局部加热SMP表面的微结构实现了空间可选择、可编写的转印，并成功将一字型、十字型和T字型硅薄膜转印到了柔性衬底。