Biodegradable Flying Sensors Revolutionize Environmental Data Collection

Their job is to monitor the state of the forest floor ecosystem, for example, and they shatter into pieces when their work is done. A bioglider modeled after the Java cucumber shoots seeds tens of meters into the air. Empa researchers developed these sustainable flight sensors from potato starch and wood waste.

Alexander von Humboldt, Charles Darwin and Ernest Shackleton embarked on years of arduous voyages of exploration, collecting spectacular impressions hitherto unknown. Today, the pioneers of modern environmental observations are being taken over by faster, more modern data collectors that record critical environmental parameters in real-time and without risk. That is why his Empa researchers at the Institute for Sustainability Robotics in Dubendorf are developing low-cost, sustainable sensors and flight devices. This sensor and flight device can collect environmental data in an energy efficient, dense and autonomous manner, even in inaccessible locations. The so-called bio he is a glider. Ingredients: Potatoes, wood chips, dyer’s lichen.

forest litmus paper

Like leaves rolling to the ground in autumn, they sail silently to the forest floor. A bioglider with built-in sensors. However, the “bio” label is applied to thin flight devices in two ways. They are inspired by biology as they are modeled after the flying seeds of the Java cucumber, but they are also biodegradable. Drones are smart as they release sensor seeds that report data on soil moisture and acidity, for example, until they eventually rot and become one with the forest floor.

A team of Empa researchers Fabian Wiesemüller and Mirko Kovac of the Sustainability Robotics lab hopes to use data from smart seeds to monitor forest soil conditions and their biological and chemical balances. The first sensor is used to measure pH values ​​with conventional litmus paper. Here, the lichen-derived dye reacts with acid, changing color from purple to red. “Changes in the color of sensors on the forest floor are recorded by drones flying over the area,” Wiesemüller explains.

sensor in full bloom

The sensor is covered with a protective film so that it is protected until it is used and collects data only at critical moments. This is a tricky “contra hood” that releases the sensor as soon as it rains. During work breaks, take a robust protective position. However, as soon as the sensor starts working, the protective film reacts very sensitively. If there is rain or moisture in the air, it will open like a flower. Working with Gustav Nyström’s team at Empa’s Institute of Cellulose & Wood Materials, researchers have developed this protective mechanism based on nanofibrillated cellulose from wood residues. It is treated with gelatin to form a microscopic polymer film that reacts to atmospheric moisture. When the rain clouds clear, the polymer bloom closes after about 30 minutes until the next cycle. To ensure that the “flowers” open symmetrically, the polymer film is also coated with a very thin layer of shellac, a natural resin-like substance excreted by plant lice. Prevents uneven expansion of polymer materials when exposed to moisture.

… on potato wings

The biosensor’s vehicle is a glider, the material of which consists of conventional potato starch, comparable to edible paper. This means you just need to print the glider and press it into the Javanese cucumber seed shape. Including sensors, the glider weighs just 1.5 grams and has a wingspan of 14 cm. “The biology-inspired design aims to allow the glider to descend for as long as possible,” robotics researcher Wiesemüller of his explains the choice of the glider’s geometry. With his Empa in Dubendorf and Imperial his College London drone airfield, Wiesemüller was finally able to optimize the flight behavior and stability of the first prototype. At the airfield, the bioglider managed to achieve a glide ratio of 6. This corresponds to a horizontal distance of 60 meters when the glider takes off from a height of 10 meters.

A race against time begins when the ultralight measuring device hits the ground. Nature starts working on it while the sensor measures the pH value every time it rains. After 7 days under laboratory conditions, the soil organism has already decomposed the wings, and after 3 weeks he breaks apart the sensor. This is how the bioglider’s natural ingredients find their way back to nature. According to Wiesemüller, the acid sensor is just an early proof of concept, followed by other types of sensors that can determine tree, water and soil conditions in real time.

dust to dust

Now researchers are going one step further. Their goal is to use fully biodegradable sensor drones to record the impact of climate change on different habitats. In the spirit of “digital ecology,” such robots can accurately predict the state of their environment, take appropriate precautions, and decompose into their parent substances in nature. So far, not all parts of such environmental drones are available in high-quality biodegradable versions. Researchers at Empa are now working with a multidisciplinary team to fly drones using an eco-friendly framework based on highly porous cellulose and gelatin materials. Bio Findings from his glider project are also incorporated here.

bio-inspired robot

They need to repair buildings and measure environmental pollution in inaccessible areas. For these tasks, artificial helpers must take inspiration from nature. Biologically-inspired flying objects still have much to learn from role models to be able to act independently in complex environments. After all, nature has spent hundreds of millions of years perfecting the properties of living organisms. Asian vines scatter their seeds with transparent wings in the wind. Like the original, the Smart Sensor Seed has a wingspan of 14 cm. Instead of a core seed, the bioglider carries sensors to collect environmental data.

Original: Delicate, industrious, fleeting

Than: Swiss Federal Institute for Materials Science and Technology