Sunday, November 28

Micro hooks based on plants – sticky herb inspires new types of adhesive structures for sensors and co –

Researchers have taken the Velcro-like adhesive structures of sticky herb as a model for new types of micro-hooks. Their hook structures, printed from resin, isomalt and other substances using 3D printing, adhere to leaf surfaces without damaging them and enable versatile applications. They hold sensors for plant monitoring on the leaf, administer protective products to the plant or even let mini robots crawl over the leaf.

The sticky herb, also called burdock bedstraw, does not bear its name for nothing. It has small bristles or hooks all over its fruits, stems and leaves that help the plant to hold onto other living things. In order to get hold of the sun and grow in the sun, the sticky herb with its bristly leaves almost parasitically attaches itself to other plants. Researchers now want to use this principle to protect plants.

As part of the EU-funded GrowBot project, scientists from the Italian Institute of Technology have developed a type of plaster based on the sticky herb as a model. The plaster has micro-hooks on its underside, which are similar to a Velcro fastener. “These micro-hooks are very versatile and allow us a large number of areas of application,” explains Isabella Fiorello, first author of the study.

Plaster from the 3D printer

In order to develop the artificial micro-hooks, the scientists first analyzed the structure and stability of the natural glutinous hooks. Then they made different variants of these adhesive structures with the help of a 3D printer. Depending on the material from which these are printed, different properties and possible uses resulted.

“The anchoring can be used for in-situ monitoring of the plant’s microclimate, i.e. temperature, humidity and light, or for the controlled release of molecules into the plant’s vascular system,” says Fiorello. The latter happens via micro-hooks made from isomalt, a sugar alcohol. With the help of this substance, the hooks can gently penetrate the cuticle of the leaves and tap into the vessels of the plant.

The researchers were able to administer protective agents or other substances to the plants locally and directly. Another advantage: Isomalt is biodegradable and leaves no traces or waste.

Resin hook sensors

Thanks to the hooks, this five-gram weight can easily be attached to the leaf surface. © Italian Institute of Technology

In addition to isomalt, the researchers also used a photosensitive resin to print microhooks. With the help of these structures, they were able to attach sensors for light, humidity and temperature directly to the plants. The resin hooks are not directly degradable, but offer a strong hold on the leaf surface without damaging it. “This opens up several application scenarios in precision forestry and agriculture,” the researchers say. “This plant-inspired technology can enhance our understanding of ecosystems and thus maintain their delicate balance.”

In addition, the researchers have also developed a micro-robot that is shaped like an upright bracket. It holds on to the leaf surface with sticky weed hooks and moves like a caterpillar. The scientists still see a lot of potential here: “The machines could be used in natural ecosystems, perhaps even in areas with high vegetation that are difficult to access. There they could climb up plants and be anchored between them to enable continuous mobile remote monitoring of the wilderness. ”(Communications Materials, 2021; doi: 10.1038 / s43246-021-00208-0)

Those: Italian Institute of Technology

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