A team of engineers from the University of California, San Diego has developed soft devices containing algae that glow in the dark when subjected to mechanical stress. The devices glow without electronics – making them ideal for building soft robots to explore dark environments.
The source of the glow is a type of single-celled algae called dinoflagellates. The team was inspired for these devices by the bioluminescent waves that sometimes appear on San Diego beaches during red tide.
“This was very interesting to me because my research focuses on the mechanics of materials — everything to do with how strain and stress affect the behavior of a material,” said Shengqiang Tsai, a professor of mechanical and aerospace engineering in UC San’s School of Engineering Diego Jacobs and senior author of the study.
Cai teamed up with marine biologist Michael Latz of UC San Diego’s Scripps Institution of Oceanography, and they injected a culture solution of the dinoflagellate Pyrocystis lunula inside a soft, stretchy, transparent material — after testing different shapes.
When the material is in any way—even mildly—pressed, stretched, or deformed, it causes the solution to flow; the mechanical stress of this flow triggers the glow. The inner surface of the material is lined with small columns for a rough inner texture; this disrupts the flow of liquid inside the material and makes it stronger. The stronger flow applies more stress to the dinoflagellates – triggering brighter light.
The team also made the devices light up by vibrating, painting on their surfaces and blowing air on them to make them move – showing the potential to be used to collect airflow to produce light. In addition, the team inserted tiny magnets into the magnetic control devices.
“Basically, they’re maintenance-free,” Kai said. “Once we inject a culture solution into the materials, that’s it. As long as they are recharged by sunlight, they can be used again and again for at least a month. We don’t need to change the decision or anything like that. Each device is its own little ecosystem – engineered living material.
“When you put living organisms in a synthetic, confined space, you have to think about how to make that space habitable — how it’s going to let air in and out, for example — while still maintaining the material properties you want,” said study first author Chenghai Li. PhD in Mechanical and Aerospace Engineering. student in Cai’s lab.
Li says the key is to make the elastic polymer porous enough that gases like oxygen can pass through without any leakage.
“This is a great demonstration of using living organisms for an engineering application,” Latz said. “This work continues to advance our understanding of bioluminescent systems from the basic research side, while laying the groundwork for a variety of applications ranging from bio-force sensors to electronics-free robotics and much more.”
Here is an interview (edited for clarity) with Cai.
Technical pants: What is the next step in your research?
Tea: We attempt to integrate bioluminescent algae into a hydrogel matrix to create responsive biohybrid materials that can then be easily manufactured in various shapes and sizes.
Technical pants: When will this technology be commercially available?
Tea: It is very difficult to predict. We are still in the proof-of-concept demonstration stage.
Technical pants: Will there be a big market for it?
Tea: We have no idea about that at this stage. We are actively looking for new applications based on our development.
Technical pants: How will this help industry and research?
Tea: Our work may enable the development of new/intelligent robots.
Technical pants: Are you working on other similar advances? projects?
Tea: Yes, our current studies are to construct soft robots using the bio-hybrid approach developed in the present study.
Technical pants: Anything else you want to add?
Tea: Biohybrid is a recently emerging approach to create new functionalities. The approach is very promising because we can directly harvest very complex biological functions that otherwise cannot be easily reproduced in the laboratory.