Design, Optimization and Production of Smart Surfaces by Additive Manufacturing for Medical Applications

Smart surfaces have attracted wide attention from research due to their special functionality, which typically cannot be achieved by a bulk material. Despite the clear potential and benefits, they have not gained widespread industrial relevance due to some fundamental challenges associated with the design, production and choice of materials to be used. In this thesis, mask-projection vat photopolymerization (VPP) was chosen as a possible technology, as it shows advantages over currently applied methods by being able to improve on factors such as fidelity, cost, complexity and its applicability to produce multi-scale,  multifunctional surfaces for high-end engineering tools like medical devices.

To apply VPP in surface manufacturing a comprehensive study on the genesis of smart surfaces and mechanisms governing photopolymerization-based manufacturing was performed. Based on the current most advanced developments, the most significant factors regarding both functionality and manufacturability were established. Furthermore, a fully open, high-resolution VPP system was employed as the main tool for surface manufacturing. To optimise the implementation of improvements the process chain was decomposed and the development of each phase was applied.

The first optimisation phase was the pre-processing stage of the chain - design and material selection. The construction of the surfaces was performed, taking into account the aspects of functionality and  manufacturability. Functionality-oriented design investigated the influence of the dimensions and shapes of critical features of the surface on the selected property (hydrophobicity). Next, the behaviour of smart surfaces on inclined structures mimicking real-life medical devices was tested. The dimensions were then adjusted to the resolution and constraints of the VPP system, i.e. the projector and vertical stage subsystems.

The last part of the chapter presents the material selection process.Design optimisation was followed by the development of the processing part, which included fabrication and post-processing. First, the methodology for the determination of the process window was outlined followed by identification of the weak points of the applied setup. With an iterative hardware upgrade, significant progress in terms of functionality and manufacturability ease was achieved. In the postprocessing phase, the influence of the cleaning and post-curing parameters were established, leading to the determination of the optimal settings.

The last part of the thesis depicts the evaluation of applied methods. The assessment of the employed techniques, parameters and hardware upgrade was undertaken, taking into account the functionality  improvement. Next, the characterisation methods relevant for the practical application of used materials were selected and performed. Lastly, the determined properties and optimised surfaces were applied in advanced applications.

The work performed in this thesis led to a significant improvement in the case of both functionality and manufacturability of smart surfaces. The obtained results showed that through a decomposition of the process chain and iteratively employed enhancements it is possible to improve special properties and accuracy. Moreover, the employment of surfaces in advanced applications revealed that it is possible to add value to the devices where specific functionality is required. Based on the undertaken work, this thesis proposes solutions that could be mainly used for surfacewater interaction, however, they can be applied for other  functionalities too.