Nature inspired surface/interface engineering towards advanced device applications

Sridhar, Sreepathy (2020) Nature inspired surface/interface engineering towards advanced device applications. Doctoral thesis, Northumbria University.

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Abstract

Nature inspired surface/interface with multi-faceted functions possess promises in the frontier engineering applications in flexible electronics, energy harvesting, autonomous systems, bio-mimicking tissues, micro-fluidics, etc. Understanding the relationship between nature’s architecture and underlying science could bring enabling solutions to overcome the engineering challenges. A nature inspired surface with smart resilient features provides intrinsic complexity and their multiplicity under different stimuli, i.e. chemical, physical, electronic, mechanical and (in some cases) biological properties. By mimicking/harvesting a variety of surface and interfacial features from nature, the final composition will display an integrative design to provide further explorations in deciphering the hidden physics towards advanced device applications in real world.

Specifically, we bring a few engineering examples with chemical/physical approaches to construct artificial nano/micro-structured surface, yield various functional surface for different application scenarios.

• A porous layer has been realised to provide controllable generation of microarchitecture to exhibit an anti-corrosion behaviour under UV exposure with multifaceted characteristics such as profound solar absorptivity, thermal emissivity. By further treating the surface with silane, a hybrid layer has been established with superhydrophobic and anti-icing features which shares innate interests in thermal transport/aero-space engineering.

• The structural conformation/ elastic instabilities of the surface are exploited to devise an extreme switchable configuration to develop a morphing strategy for switchable lipophilic/oleophobic properties. The geometrical shift of soft structure is instructed to create a steady transition of surface topology rendering a unique switchable transition that are widely inspired in sub-sea/offshore engineering for oil and water separation.

• We also develop a highly-replenishable thermal energy harvesting technology via a dynamical elasto-bouncing process of polymeric hydrogel to translate the thermal energy into useful elasto-kinetic energy, then further converted into electrical energy via a simple piezo-material based system, which paves way for a future portable and conformable energy harvesting tool in the regions of extreme geo-thermal residencies and industries.

• Using a one drop filling technique along with interfacial pinning points between hydrophilic and hydrophobic, a unique microfluidic approach is presented to create heterogenous structures. By exploiting the communication between swelling mismatch of different functional groups, driven via in-plane and through thickness heterogeity, a highly complex 3D soft reconfiguration is achieved which is activated by stimulation inputs.

• The theoretical understandings are exploited in the above applied engineering scenarios, such as elastic mechanics, morphing structure, surface/interface interactions and kinetics of of the polymer systems experienced on a hot surface, which offers further insights into the elastic recoiling evolution and tunability of the system for effective energy translation efficiency.

We hope above approaches shed more lights on the nature inspired structure in device engineering, thus, advance the knowledge in the frontier science.

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