Examples of shapes made from the novel soft, living materials, which glow in response to mechanical stress. Image: UC San Diego Jacobs School of Engineering.A team led by researchers at the University of California (UC) San Diego has developed soft yet durable materials that glow in response to mechanical stresses such as compression, stretching or twisting. The materials derive their luminescence from single-celled algae known as dinoflagellates.
The researchers report their work, which was inspired by the bioluminescent waves observed during red tide events at San Diego’s beaches, in a paper in Science Advances.
“An exciting feature of these materials is their inherent simplicity – they need no electronics, no external power source,” said Shengqiang Cai, a professor of mechanical and aerospace engineering at the UC San Diego Jacobs School of Engineering and senior author of the paper. “We demonstrate how we can harness the power of nature to directly convert mechanical stimuli into light emission.”
This study was a multi-disciplinary collaboration involving engineers and materials scientists in Cai’s lab, marine biologist Michael Latz at UC San Diego’s Scripps Institution of Oceanography and physics professor Maziyar Jalaal at the University of Amsterdam in the Netherlands.
The primary ingredients of the bioluminescent materials are dinoflagellates and a seaweed-based polymer called alginate. The researchers mixed these elements to form a solution, which was then processed with a 3D printer to create a diverse array of shapes, such as grids, spirals, spiderwebs, balls, blocks and pyramid-like structures. The 3D-printed structures were then cured as a final step.
When the materials are subjected to compression, stretching or twisting, the dinoflagellates within them respond by emitting light. This response mimics what happens in the ocean when dinoflagellates produce flashes of light as part of a predator defense strategy. In tests, the materials glowed when the researchers pressed on them and traced patterns on their surface. The materials were even sensitive enough to glow under the weight of a foam ball rolling on their surface.
The greater the applied stress, the brighter the glow. The researchers were able to quantify this behavior and developed a mathematical model that could predict the intensity of the glow based on the magnitude of the mechanical stress applied.
The researchers also demonstrated techniques to make these materials resilient under various experimental conditions. To reinforce the materials so they could bear substantial mechanical loads, the researchers added a second polymer, poly(ethylene glycol) diacrylate, to the original blend. Also, they found that coating the materials with a stretchy rubber-like polymer called Ecoflex provided protection in acidic and basic solutions. With this protective layer, the materials could even be stored in seawater for up to five months without losing their form or bioluminescent properties.
Another beneficial feature of these materials is their minimal maintenance requirements. To keep working, the dinoflagellates within the materials just need periodic cycles of light and darkness. During the light phase, they photosynthesize to produce food and energy, which are then used in the dark phase to emit light when mechanical stress is applied. This behavior mirrors the natural processes at play when the dinoflagellates cause bioluminescence in the ocean during red tide events.
“This current work demonstrates a simple method to combine living organisms with non-living components to fabricate novel materials that are self-sustaining and are sensitive to fundamental mechanical stimuli found in nature,” said Chenghai Li, a mechanical and aerospace engineering PhD candidate in Cai’s lab and first author of the paper.
The researchers envision that these materials could potentially be used as mechanical sensors to gauge pressure, strain or stress. Other potential applications include soft robotics and biomedical devices that use light signals to perform treatment or controlled drug release.
However, there is much work to be done before these applications can be realized. The researchers are working on further improving and optimizing the materials.
This story is adapted from material from the University of California, San Diego, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.