面向微转印技术的界面力学行为及黏附调控研究

Micro-transfer printing is a technique relying on the interface adhesion for integrating functional devices by transferring prefabricated micro/nano-elements from the growth donor substrate to the target substrate, which plays an important role in the fabrication process of flexible inorganic electronics. The key for improving this technique lies in the precise prediction and regulation of adhesion in the stamp/transferred element interface and the transferred element/substrate interface. For this problem, investigations of the interfacial mechanical behavior and regulation of adhesion for the micro-transfer printing technique will be conducted in this project. Firstly, the mechanical model for the stamp/transferred element/substrate system will be established considering the competitive delamination mechanism between interfaces, intermolecular interaction and viscoelastic property of the stamp and the target substrate. Variations of the interfacial mechanical behavior during the pickup and printing steps will be illustrated and the judging criterion for the competitive delamination between interfaces will be established. And then, the adhesion theory for contact between the viscoelastic stamp with micro/nanostructures and the transferred element will be improved considering the scale effect. The adhesion adjusting mechanism of micro/nanostructures will be examined and design strategies of micro/nanostructured stamps will be proposed. Eventually, a measurement setup for quantifying the interfacial mechanical behavior of the micro-transfer printing system will be built. Experimental studies will be conducted and results will be compared with theoretical ones. Through the study of this project, theoretical bases and technical supports will be provided for improving the yield of micro-transfer printing technique and promoting its further application.

微转印技术是利用界面黏附作用将预加工好的微/纳单元从其生长的源基体有序转印至目标基体，形成功能器件的技术，在柔性无机电子器件的制造过程中起着重要作用。该技术提升的关键在于印章/被转印单元界面和被转印单元/基体界面黏附的精确预测和调控。针对此问题，本项目开展面向微转印技术的界面力学行为及黏附调控研究：首先，构建考虑界面间竞争分层机制、分子间作用力和印章及目标基体材料粘弹特性的印章/被转印单元/基体系统力学模型，揭示转移和印制过程中界面力学行为的变化规律，建立界面间竞争分层的判定准则；其次，考虑尺度效应完善表面具有微/纳结构的粘弹性印章/被转印单元黏附接触理论，揭示微/纳结构调控界面黏附的机理，提出印章表面微/纳结构的设计策略；最后，搭建微转印系统界面力学行为测试平台，开展实验研究，对理论模型进行对比论证。通过本项目研究为提高微转印技术的成功率及其进一步推广应用提供必要的理论基础和技术支持。

微转印技术是材料组装和微/纳制造领域的先进方法，其利用界面微观黏附作用，通过粘弹性印章将微/纳单元从其生长的源基体有序转印至目标基体上，最终形成功能器件。但是，由于印章材料的特殊性以及被转印单元的多样性，转印过程的工艺参数控制仍然困难，转印成功率仍有待提升。本项目以预测转印成败和解决转印失败为研究目标，开展了如下研究：（1）建立了印章/球形被转印单元粘弹性黏附接触力学模型，模拟分析发现印章/被转印单元界面最大黏附力随卸载速度、预压载荷和黏附功的增加而增大；提出了以印章/被转印单元界面和被转印单元/基体界面最大黏附力的相对大小作为界面竞争分层的判定准则，研究发现目标基体材料不同，可实现成功转印的界面黏附功和压入深度范围不同，且黏附功越大或压入深度越小，临界剥离速度越大。（2）建立了印章/硅纳米膜界面和硅纳米膜/基体界面内聚力模型，模拟分析发现印章/硅纳米膜界面和硅纳米膜/目标基体界面的断裂韧性均需满足一定范围才可实现成功转印，且印章和目标基体材料均会影响转印成败。（3）建立了结构化粘弹性印章/硅纳米膜界面黏附力学模型，模拟结果发现相同微结构尺寸下，棱锥形微结构的黏附调控比大于圆柱形微结构，更适合用于微转印技术中；黏附调控比随圆柱形微结构和棱锥形微结构尺寸的变化规律呈现完全相反的趋势；随微结构间距的增加，黏附调控比有先减小后增大的趋势，存在使黏附调控效果最佳的微结构间距。（4）搭建了微转印系统界面力学行为测试平台，试验结果发现卸载速度对球形印章/硅界面最大黏附力的影响比其对平印章/硅界面或圆柱形微结构化印章/硅界面最大黏附力的影响要显著；预压载荷对平印章/硅界面或圆柱形微结构化印章/硅界面最大黏附力的影响比其对球形印章/硅界面最大黏附力的影响要显著。本项目的研究成果为提高微转印技术的成功率及其进一步推广应用提供了必要的理论基础和技术支持。