Smarter farming: Silk needles heal crops with precision

Agricultural chemicals sprayed over vast plant fields rarely stay where growers intend. Researchers estimate that as much as half of each application drifts into soil, water, or the atmosphere – raising costs for farmers while burdening ecosystems.

A collaboration between MIT and the Singapore-MIT Alliance for Research and Technology offers a radically different approach: hollow microneedles spun from natural silk protein that inject fertilizers, nutrients, or sensing probes directly into plant tissues.

This technique pairs surgical precision with a fabrication process so simple it can be done outside a clean room, yet robust enough for large-scale production.

Silk needles for smarter farming

“Agrochemicals are important for supporting our food system, but they’re also expensive and bring environmental side effects, so there’s a big need to deliver them precisely,” explained Benedetto Marelli, the study’s senior author and an associate professor of civil and environmental engineering at MIT.

Traditional foliar spraying addresses entire canopies even when only specific plants – or particular tissues – need treatment.

The new silk microneedles bypass that waste, ferrying liquids directly into a plant’s vascular network, where they can be distributed internally with minimal losses to the surrounding environment.

A new way to feed plants

The research builds on medical microneedle technology originally devised for painless human vaccinations. Earlier work from Marelli’s group proved that solid silk needles could pierce plant epidermis, but those prototypes carried only minuscule doses.

To deliver commercially relevant volumes, Yunteng Cao and Doyoon Kim created a hollow version without the clean-room lithography medical devices usually require. They mixed purified silk fibroin with a saline solution and cast the blend into tiny conical molds.

As the water evaporated, salt crystallized inside the cones. Washing away the salt left behind either a central lumen or microscopic pores, depending on salt concentration. Despite their lightweight structure, the needles still had enough strength to penetrate stems.

“It’s a pretty simple fabrication process. It can be done outside of a clean room – you could do it in your kitchen if you wanted,” Kim said.

Using silk needles to heal crops

Iron deficiency, or chlorosis, stunts growth in many crops and can significantly reduce tomato yields. Sprays often fail because iron oxidizes before it enters the roots or leaves.

The team demonstrated that their hollow needles could infuse iron chelate directly into chlorotic tomato stems, reversing yellowing while using far less material than conventional soil or foliar supplements.

Because the silk matrix biodegrades over several days, the needles acted like slow-release capsules, sustaining iron delivery as the plant recovered.

Enriching crops with vitamins

Biofortification – boosting the nutritional content of crops – typically involves genetic engineering or post-harvest additives.

The researchers tested whether the silk microneedles could embed vitamin B12, a nutrient scarce in plant foods, into developing tomatoes. Injections into green stems resulted in ripe fruit containing measurable B12, hinting at a field-based route for nutrient enrichment.

Co-author Daisuke Urano noted that detailed assessments showed “minimal adverse effects from microneedle injections in plants, with no observed short- or long-term negative impacts,” suggesting the method could scale without compromising crop health.

Crop diagnostics and silk needles

The team also used the needles as diagnostic probes. Hydroponic tomatoes growing in cadmium-tainted nutrient solution can absorb the toxic metal long before visual symptoms appear.

By inserting microneedles and later analyzing the absorbed sap, the researchers detected cadmium within fifteen minutes and monitored its rise over eighteen hours.

Current imaging methods only reveal stress after growth falters, and pulling sap manually is laborious. A microneedle array could act as an “IV line,” continually sampling fluid for on-farm analytics.

Robotic treatment for plants

At present, technicians place the needles by hand, but Marelli envisions mounting them on robotic arms or autonomous drones that already patrol high-tech farms. Such systems could target individual plants flagged by imaging or soil sensors, applying nutrients or pesticides only where needed.

“We want to maximize the growth of plants without negatively affecting the health of the farm or the biodiversity of surrounding ecosystems,” Marelli said. “There shouldn’t be a trade-off between the agriculture industry and the environment. They should work together.”

While agriculture is the immediate focus, the underlying manufacturing technique could benefit human medicine.

Hollow polymeric microneedles loaded with drugs or vaccines can offer painless, self-administrable alternatives to hypodermic needles. Cao noted salt-templating can customize pore size and shape for controlled release in both skin and plant stems.

Precise crop injections with silk needles

Global demand for food is climbing even as arable land and freshwater resources strain under climate change and pollution. Precision tools that conserve inputs while protecting surrounding ecosystems are crucial, and silk microneedles offer a versatile platform.

The technology cuts waste and boosts crop care by infusing treatments, enriching nutrients, and enabling fast, in-plant diagnostics.

If automated at scale, farmers could soon replace broad sprays with pinpoint injections, feeding a growing world more responsibly and efficiently.

The study is published in the journal Nature Nanotechnology.

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