"Prior art is any evidence that your invention is already known.
Prior art does not need to exist physically or be commercially available. It is enough that someone, somewhere, sometime previously has described or shown or made something that contains a use of technology that is very similar to your invention." European Patent Organization https://www.epo.org/learning-events/materials/inventors-handbook/novelty/prior-art.html
To thoroughly investigate a design idea, a comprehensive approach that explores the design from a number of practical angles is needed.
Prior Art: Patents and scholarly literature describing existing designs similar to the idea that you have.
Regulatory Environment: What rules and regulations will apply to your design idea and manufacture process? In the US? In Europe? In Asia? What standards apply to your design idea? How do those standards impact specific detailed design decisions? What materials are required to meet industry standards?
Stakeholder constraints and criteria: Who are the stakeholders for this design? What constraints or criteria do they have for this design project?
Bioprocesses and medical fundamentals:What constraints are placed upon the design by existing known medical fact? In what areas will knowledge about body processes need to be extended in order to complete and/or perfect the design?
Economic/Busines/Marketing environment, including costing: What is the potential market for this design/process/product? What are the available funding sources for brining your idea to market? What will the cost of production and materials be for your design?
Materials/Manufacturing Process: What tools and techniques of manufacturing will be used in your design? What innovations in manufacture or materials are a possibility?