Designing with decay: From environmental transformation to programmed degradation in a yeast-cellulose biohydrogel for circular architectural applications

Abstract As architectural design paradigms shift from century-lasting, fossil-based construction materials toward regenerative, biogenic solutions with much shorter life cycles, a novel opportunity opens for design with material temporality and transformation. Taking a fully biobased yeast-cellulose-alginate-glycerol composite hydrogel as a case, this study examines how physical and visual properties change under air, soil, and water exposure by measuring mass loss, shrinkage, deformation, embrittlement, and color change in manually and robotically extruded constructs from this material. The results reveal distinct patterns of swelling, contraction, structural distortion, surface brittleness, and chromatic shifts that affect the designs across different exposure conditions. Together, these patterns establish a preliminary knowledge basis for architectural design that could accommodate these transitions, demonstrated in a speculative, conceptual architectural design proposal leveraging transformation and decay as part of the design. By situating material temporality as informative rather than detrimental, the study exemplifies how environmentally responsive biomaterials can support circular architectural biodesign.