Interaction effects between fungi and hydrogel antifungal coating under microgravity-induced diffusion limitation

The long-term performance of antifungal coatings in microgravity is critical for spacecraft applications, yet how altered mass transport regulates fungus–coating interactions and coating degradation remains unclear. Here, a hydrogel antifungal coating (SDM) on aluminium alloy coupons was evaluated against Aspergillus brasiliensis during a 90-day parallel experiment conducted aboard the China Space Station (CSS) and under ground conditions. We reveal that microgravity-induced diffusion limitation does not simply enhance or suppress antifungal performance but reshapes fungus–coating interfacial interactions. Restricted transport reduced fungal colonisation, while incomplete hydration-layer formation under microgravity resulted in a lower anti-biofilm adhesion rate (52.83%) than that under ground conditions (57.44%). Meanwhile, fungal stress adaptation increased organic acid production, but limited interfacial transport reduced the accumulation and action of corrosive metabolites, mitigating coating degradation. Consistent with this mechanism, chemical structure analysis showed attenuated carbonyl-related degradation signals in space-exposed coatings, whereas ground coupons exhibited more pronounced structural deterioration. These findings reveal a diffusion-controlled mechanism governing the antifungal and degradation behaviour of functional coatings under microgravity.