Patterned 3D-printed hydrogel as a novel soilless substrate for plant cultivation
Plant roots need water, micronutrients, and oxygen to maintain cellular metabolism and tissue growth, yet traditional hydroponic systems often lack sufficient oxygen delivery. While 3D printing artificial substrates has been explored to mimic the physical structure of soil, it remains unclear which design parameters are critical for supporting full plant development. Here, we present a synthetic, soilless substrate based on 3D-printed hydrogels incorporating triply periodic minimal surface (TPMS) patterns to create internal air-filled channels. These channels are open to the atmosphere, enabling passive gas exchange throughout the substrate. We tested five TPMS geometries (Lidinoid, Split-P, Schwarz-D, Schwarz-P, and Schoen), each with a near-identical hydrogel volume but with different surface-to-volume ratios. Arabidopsis thaliana seeds germinated directly on the substrates and were monitored for vegetative and reproductive growth over five weeks. Among the designs, the Lidinoid substrate led to the highest number and surface area of leaves, exceeding the aerated hydroponic control in leaf area over most of the time course; it also produced the earliest and most complete flowering, which neither control achieved in the same amount of time. Our results indicate that the surface-to-volume ratio is a key parameter influencing substrate performance; we hypothesise that this reflects its effect on oxygen availability at the root interface, which we did not measure directly. Plants grown on substrates with higher surface areas transitioned to flowering more reliably and rapidly, with flowering efficiency showing a strong positive correlation with surface area. These findings suggest that interconnected air-channel architectures can support full plant development without active aeration, potentially by overcoming the oxygen limitations of traditional hydroponic systems. This work supports the use of additive manufacturing as a powerful tool for engineering soil analogues tailored for indoor agriculture. By combining passive aeration with hydration and nutrient delivery, patterned hydrogels offer a promising, scalable solution for sustainable soilless plant cultivation.