Bidirectional Plant‐Microneedle Responses to Guide Biomaterial Design

ABSTRACT Designing biomaterials compatible with plants and specific payloads enables new technologies for precision agriculture, including targeted and dose‐controlled agrochemical delivery that overcomes the runoff, drift, and cuticular exclusion limiting conventional methods. However, broader implementation requires a systematic understanding of the complex interactions among payloads, biomaterial properties, and plant responses to establish design principles that support a sustained biotic–abiotic interface. Using microneedles made of different polymers and microstructures, this study investigates plant–biomaterial interactions to develop effective compound delivery strategies. Biodegradation studies show that microneedle biomaterials impart distinct mechanical strength, hydrophilicity, and surface charge, influencing the release of bioactive cargo. Transcriptomic analyses reveal a largely shared acute response to microneedle injection, with some material‐ or structure‐dependent variation in immunity and metabolism. Mid‐term biochemical responses show corresponding differences in membrane integrity and antioxidant activity. Despite these responses, microneedle treatments caused minimal effects on plant growth, chlorophyll content, stomatal conductance, and quantum efficiency of photosystem II. Finally, we demonstrate how biomaterial properties influence agrochemical delivery using hydrophilic plant growth regulator gibberellic acid (GA 3 ) and hydrophobic herbicide pelargonic acid (PA), into tomato and lettuce, respectively. These findings establish principles for engineering plant‐biomaterial interfaces to accommodate payloads with diverse characteristics while ensuring plant safety.