A dissolving patch delivers beneficial microbes into leaves and stems, speeding growth in vegetables while using over 15 per cent less biofertiliser than soil application
Researchers at the National University of Singapore (NUS) have developed dissolving microneedle patches that deliver living “biofertiliser” straight into plant tissue. In greenhouse tests, Choy Sum and Kale grew faster — by shoot biomass, leaf area and height — while using over 15 per cent less biofertiliser than standard soil inoculation.
The approach points to more precise fertiliser delivery, less waste and potentially lower off-target environmental impact, with near-term fit for urban and vertical farms and for high-value crops that benefit from controlled dosing.
Biofertiliser, which contain beneficial bacteria and fungi that help crops absorb nutrients and tolerate stress, are usually added to soil. There, they must compete with native microbes and can be hindered by acidity and various other conditions. Much of the input never reaches the roots. By placing beneficial bacteria or fungi directly into leaves or stems, the new method developed by the NUS team bypasses those hurdles and accelerates early gains.
“Inspired by how microbes can migrate within the human body, we hypothesised that by delivering beneficial microbes directly into the plant’s tissues, like a leaf or stem, they could travel to the roots and still perform their function, but much more effectively and be less vulnerable to soil conditions,” said Assistant Professor Andy Tay from Department of Biomedical Engineering at the College of Design and Engineering at NUS, and Principal Investigator at the Institute for Health Innovation & Technology (iHealthtech), who led the work. The study was published in Advanced Functional Materials on 13 September 2025.
Gentle delivery
The team fabricated plant-tuned microneedles from polyvinyl alcohol (PVA), a biodegradable, low-cost polymer. For leaves, a 1 cm by 1 cm patch carries a 40 by 40 array of pyramids about 140 μm long, while a short row of roughly 430-μm needles suits thicker stems. Microbes are blended into the PVA solution, cast into tiny moulds and locked in the needle tips. Pressed by the thumb or with a simple handheld applicator that spreads force evenly, the needles slip into plant tissue and dissolve within about a minute, releasing their microbial cargo.
In laboratory tests, the patch barely disturbed plant tissue or function. Shallow indentations in leaves faded within two hours; chlorophyll readings remained stable; and stress-response gene expression, which briefly rose after insertion, returned to baseline within 24 hours. The patches maintained high microbial viability after storage for up to four weeks – this means the patches can be prepared in advance – and importantly, loading concentration translated to delivered dose, which enables controlled application that is difficult to achieve in soil. A 3D-printed applicator provided uniform insertion across large leaf areas and could become an integral component in future robotic automation.
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