Scientists Draw Inspiration From Catchweed To Create Biodegradable Velcro

An anonymous reader quotes a report from Ars Technica: Velcro is an ingenious hook-and-loop fastener inspired by nature -- specifically, cockleburs. Now scientists at the Italian Institute of Technology are returning the favor. They have created the first biodegradable Velcro -- inspired by climbing plants -- and used it to build small devices to help monitor the health of crop plants and deliver pesticides and medicines as needed, according to a November paper published in the journal Communications Materials. Co-author Isabella Fiorello and her colleagues were interested in developing innovative new technologies for monitoring plants in situ to detect disease, as well as delivering various substances to plants. However, few such devices can be attached directly to plant leaves without damaging them. The best current options are sensors attached with chemical glues, or with clips. There are also micro-needle-based patches under development able to penetrate leaves for disease detection. Fiorello et al. found inspiration in the common catchweed plant (Galium aparine). It can form dense, tangled mats on the ground, and while the plants can grow up to six feet, they can't stand on their own and instead must use other plants for support. For this purpose, catchweed plants rely on a 'unique parasitic ratchet-like anchoring mechanism to climb over host plants, using microscopic hooks for mechanical interlocking to leaves,' the authors wrote.

The Italian team closely studied that micro-hook structure and then used a high-resolution 3D printer to create artificial versions, using various materials -- including photosensitive and biodegradable materials made from a sugar-like substance known as isomalt. Their artificial reproductions proved quite capable of attaching to many different plant species, just like their natural counterparts. As an initial application, the team designed a device that could penetrate a plant cuticle with minimal invasiveness, thereby enabling the plant to be monitored and treated, if necessary. The isomalt microhooks attach to the vascular system of leaves and then dissolve inside, because isomalt is soluble. Fiorello et al.'s experiments demonstrated that their artificial micro hooks can be used as a plaster for targeted, controlled release of pesticides, bactericides, or pharmaceuticals onto the leaves. This would greatly reduce the need for broad application of pesticides. And since the plaster dissolves once it's applied, there is no additional waste.

The team also printed hooks made out of a photosensitive resin and assembled them together with sensors for light, temperature, and humidity to make intelligent clips to enable wireless monitoring of the plant's heath. The clips attach to individual leaves, transmitting data wirelessly thanks to customized computer software. The prototype proved resistant to windy conditions and was capable of making real-time measurements for up to 50 days. The devices could be used for small-scale botanical applications, or they could be scaled up. For instance, farmers could distribute many such devices to better map and monitor wide cultivation areas, according to the authors. Finally, Fiorello et al. developed a micro-robotic system capable of moving over the surface of leaves using micro steps, copying the ratchet-like motion of the catchweed plant. Similar actuation mechanisms have previously been demonstrated in Stanford University's SpinyBot -- capable of scaling hard, flat surfaces thanks to arrays of miniature spines on its feet -- and the University of California, Berkeley's CLASH robots, which are capable of climbing up loose suspended cloth surfaces, like curtains.

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