What all is needed to fabricate a new sensor component, using microneedles as a case study. Raw concept idea, expected specifications, defining the uncertainties, when to include the foundry. Collaboration is vital to identify the unknowns in function and fabrication and to prepare needed design variants to derisk the prototypes and achieve informative results as early as possible. And with first results come specification refinement, what should the end function really be? Learning through a biomedical micro needle implant project.