Self-Healing of Biomineralized Engineered Living Building Materials

Living building materials (LBMs) are an emergent class of structural materials that leverage the biomineralization capability of microorganisms within sand-hydrogel scaffolds to produce living, load-bearing structures. In this study, we produced LBMs using a physically crosslinkable hydrogel-sand scaffold and two microorganisms with different biomineralization pathways—<i>Sy</i><i>nechococcus sp. </i>PCC 7002 (photosynthetic) and <i>S. pasteurii </i>(ureolytic)—and investigated their self-healing capacity. Our results reveal that both <i>Synechococcus sp. </i>PCC 7002 and <i>S. pasteurii</i> demonstrated exceptional viability within all LBMs for more than 20 days. LBM prisms were pre-loaded to 40% of their structural capacity in compression or flexure. Damaged LBMs containing <i>Synechococcus sp. </i>PCC 7002 exhibited a full rebound of their original compressive and flexural strengths, respectively, after three days of healing at 50% relative humidity (RH) (<i>i.e.</i>, ambient conditions). In contrast, LBMs containing <i>S. pasteurii </i>exhibited marginal recovery of their original compressive and flexural strengths, respectively, after three days of healing at 50% RH. The compressive and flexural strengths of all LBMs fully rebounded after seven days of healing at 50% RH. Results substantiate that the self-healing ability of the hydrogel alone plays a critical role in facilitating healing of LBMs, as evidenced by high rebounds in compressive and flexural strengths by the hydrogel-sand scaffold after three or seven days of healing 50% RH.