Development of Hierarchical Micro/Nano Structured Multi-Responsive Surfaces for Microfluid Applications

刺激响应涂层的最新进展使其能够作为功能元件集成在纳米技术中，如微流体、微电子机械系统(MEMS)，在这些技术中，由于大的比表面积比，界面力强烈地影响着器件的性能。然而，响应性涂层的主要缺点是：(I)缺乏响应性、快速性、选择性和可逆性，(Ii)环境稳定性差，(Iii)对结构-功能关系的了解有限，这些都是设计可靠的多功能表面规则的关键。该计划利用表面化学、聚合物科学和自组装的方法，旨在通过开发和研究新一代响应性层次化微/纳米结构涂层来克服这些限制，这种涂层的物理性能(结构和机械性能)和表面化学可以根据不同的外部刺激(光、温度、pH、离子强度)进行独立和可逆的调整。*所提出的微结构由永久附着在衬底上的2D纳米凝胶阵列组成，其大小和弹性(通过膨胀/收缩行为)可以通过温度或光来调节，从而允许可逆地控制表面形貌(粗糙度)和硬度。纳米凝胶表面将使用聚合物刷子进行功能化，根据所需的自适应精细表面特性，可以使用不同的刺激(pH、离子强度或温度)来独立控制其纳米结构和化学成分。这种显微组织有望增强外层刷层的表面化学效果。该计划将涉及四个方面：(I)开发和优化利用不同聚合物刷子功能化的热响应2D纳米凝胶阵列；(Ii)开发和优化表现出显著膨胀效应的光响应纳米凝胶并将其固定到2D阵列中；(Iii)研究和优化在(I)和(Ii)中开发的涂层对不同刺激的响应行为；以及(Iv)探索作为微流体中流体控制功能元件的潜在应用。*所提出的分级纳米/微结构的各种调制方式将最有可能实现革命性的进步和新技术的创造，特别是在生物医学表面工程和微流控领域，这些领域越来越需要先进的小型功能部件组装。

Recent advances in stimuli-responsive coatings enable their integration as functional elements in nanotechnologies such as microfluidics, Micro Electro-Mechanical Systems (MEMS) where interfacial forces strongly influence the device performance because of the large surface-to-volume ratio. However, responsive coatings are suffering from major shortcomings: (i) lack of responsiveness rapidity, selectivity and reversibility, (ii) poor environmental stability, (iii) limited understanding of the structurefunction relationship, which are all critical to design reliable rules for building multifunctional surfaces. Using approaches from surface chemistry, polymer sciences and self-assembly, the proposed program aims to overcome these limitations by developing and investigating a new generation of responsive hierarchical micro/nano-structured coatings whose physical properties (structure and mechanical properties) and surface chemistry can be tuned independently and reversibly using different external stimuli (light, temperature, pH, ionic strength). ***The proposed microstructure consists of 2D nanogel arrays permanently attached to substrates and whose size and elasticity (via swelling/shrinking behavior) can be modulated by temperature or light allowing surface topography (roughness) and stiffness to be reversibly controlled. The nanogel surface will be functionalized with polymer brushes whose nanostructure and chemistry can be independently controlled using different stimuli (pH, ionic strength or temperature) depending on the desired adaptive fine surface properties. The microstructure is expected to enhance the effect of surface chemistry of the outer brush layer. The program will involve four aspects: (i) development and optimization of thermo-responsive 2D nanogel arrays functionalized with different polymer brushes, (ii) development and optimization of photo-responsive nanogels exhibiting significant swelling effects and their immobilization into 2D arrays, (iii) investigation and optimization of the responsive behavior of the coatings developed in (i) and (ii) towards different stimuli and (iv) exploration of potential applications as functional elements for fluid control in microfluidics.***The various ways the proposed hierarchical nano/micro structures can be modulated will most likely enable revolutionary advances and creation of new technologies, particularly in biomedical surface engineering and microfluidics where advanced assembly of small functional components are increasingly required.*****