Collaborative design prototyping in transdisciplinary research: An approach to heterogeneity and unknowns

•Research through design engages in complex research problems by applying design methods.•Design prototyping supports integration and knowledge co-production in transdisciplinary teams.•The interweaving of design thinking and design doing has transformative potential.•Design prototyping appoaches the unknowns of complex problems through openness and iteration.•Conceptual desings complement linguistic expressions through language of forms.