Production of titanium oxide added graphene composite slippery surfaces and determination of smart material performance

Smart materials are materials that respond intelligently to environmental changes, such as external stimuli (temperature, humidity, electric fields, magnetic fields, light, etc.), and can alter their shape, size, or properties in response to these effects. The ability of smart materials to respond intelligently to external stimuli is crucial, especially in dynamic and environmentally sensitive fields such as medical devices, robotic systems, automatic control systems, and energy efficiency applications. The use of composite materials as smart materials is important due to their potential to respond to different stimuli or generate more efficient responses. Therefore, graphene, with its superior properties such as excellent optical transparency, thermal conductivity, and elastic modulus, and titanium dioxide (TiO2), with its exceptional photocatalytic, electrical, mechanical, and chemical durability, have been used as composite material combinations. This aims to combine the superior properties of graphene and titanium dioxide for enhanced performance. This thesis aims to produce Graphene-TiO2 slippery surfaces with varying degrees of hydrophobicity and roughness, analyze their performance, and determine their smart responsive behavior capacities in response to external stimuli. To achieve the objectives of the thesis, Graphene-TiO2 composite surfaces were first produced by coating flat, rough, and micro-patterned substrates with GO-TiO2 dispersions at different TiO2 doping ratios, followed by reduction through chemical, chemical+thermal, thermal, or thermal+chemical methods. Micro-patterned surfaces were produced on PDMS substrates replicated from Si-wafer master molds using lithography. Subsequently, slippery surfaces were generated by impregnating lubricating liquids to ensure the stability and self-healing capability of the Graphene-TiO2 surfaces. Finally, the sliding performance of the produced Graphene-TiO2 slippery surfaces was analyzed, and manipulations were performed to control the speed and orientation of liquid droplets on the surfaces using low-voltage electrical stimuli as an external factor. To better understand the slippery surface performance and smart response behavior, parameters such as lubricant viscosity, test liquid type, droplet volume, and the applied electrical potential were examined. As a result of the conducted studies, it was found that the liquid droplet on the produced Graphene-TiO2 slippery surfaces could be controlled and moved in a controlled manner through external stimulus control. In conclusion, it has been demonstrated that the smart control of droplet movement on slippery surfaces can be achieved by optimizing surface properties from the substrate and composite, lubricant viscosity and type, and surface conductivity. Graphene-TiO2 slippery surfaces have the potential to serve as a new smart material for applications in micro-harvesting, microfluidic systems, and sensors.