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

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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 structure–function 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.*****