Italian researchers have created a novel 4D-printed biodegradable soft robot shaped like a seed that changes shape in response to changes in humidity and can navigate through the soil. The device has great potential as a new way of monitoring the environment.
4D printing is the process of using 3D printing to create objects that can change their shape or properties in response to environmental factors such as light and temperature. The technology has been used previously to create self-assembling, programmable material technologies.
Now, 4D technology has been used to create a soft robot capable of analyzing the soil. Drawing inspiration from the seed structure of the South African geranium (Pelargonium appendiculatum), which changes shape in response to environmental humidity, researchers at the Istituto Italiano di Tecnologia in Genova made the first biomimetic, biodegradable seed robot.
“Our studies started from the observation of nature, with the aim to imitate the strategies of living beings or their structures and replicate them in robotic technologies with low environmental impact in terms of energy and pollution,” said Barbara Mazzolai, corresponding author of the study.
The seeds of the Gerianaceae family of flowering plants, which includes geraniums, exploit their hygroscopic (humidity-activated) properties by detaching themselves under the right environmental conditions. After detaching, they change shape and independently penetrate the soil, increasing the chances of germination.
After thoroughly investigating the structure and biomechanics of the natural seed, researchers replicated it using a combination of 3D printing and electrospinning techniques. Electrospinning is a method of fiber production that uses electric force to draw charged polymers up to fiber diameters, in the order of some hundred nanometers.
The researchers used fused deposition modeling (FDM) to print a substrate layer comprised of polycaprolactone (PCL), a biodegradable thermoplastic polyester, that was activated using oxygen plasma to make it more water-attracting (hydrophilic). Then they added to the substrate electrospun hygroscopic fibers composed of a polyethylene oxide shell and a cellulose nanocrystal core.
On testing, the soft robot explored a soil sample, adapting its shape to interact with its roughness and cracks. It was very energy efficient and could lift around 100 times its weight.
The below video, produced by Istituto Italiano di Tecnologia, demonstrates how the robot seed responded to the soil during testing.
The novel device offers a new way of unobtrusively monitoring the planet, say the researchers.
“With this latest research, we have further proved that it is possible to create innovative solutions that not only have the objective of monitoring the well-being of our planet, but that do so without altering it,” Mazzolai said.
The researchers are hopeful that the device’s low cost, simple design and data-collecting capabilities will be particularly useful in remote areas.
“These biodegradable and energy-autonomous robots will be used as wireless, battery-free tools for surface soil exploration and monitoring,” said Luca Cecchini, first author of the study. “This bioinspired approach has allowed us to create low-cost instruments that can be used to collect in-situ data with high spatial and temporal resolution, especially in remote areas where no monitoring data are available.”
The study was published in the journal Advanced Science.
Source: Istituto Italiano di Tecnologia
