A team of University of California San Diego engineers has developed soft devices containing algae that glow in the dark when under mechanical stress. The devices light up sans electronics — making them perfect for building soft robots to explore dark environments.
The glow’s source is a type of single-celled algae called dinoflagellates. The team took its inspiration for these devices from the bioluminescent waves that sometimes occur at San Diego beaches during red tide.
“This was very interesting to me because my research focuses on the mechanics of materials — anything related to how deformation and stress affect material behavior,” said Shengqiang Cai, Professor of Mechanical and Aerospace Engineering at the UC San Diego Jacobs School of Engineering, and the study’s Senior Author.
Cai teamed up with UC San Diego Scripps Institution of Oceanography Marine Biologist Michael Latz, and they injected a culture solution of the dinoflagellate Pyrocystis lunula inside of a soft, stretchy, transparent material — on the heels of testing a variety of shapes.
When the material is in any way — even softly — pressed, stretched, or deformed, it causes the solution to flow; the mechanical stress from that flow triggers the glow. The inner surface of the material is lined with small pillars for a rough inner texture; this disturbs the fluid flow inside the material and makes it stronger. A stronger flow applies more stress to the dinoflagellates — triggering a brighter glow.
The team also made the devices glow via vibration, drawing on their surfaces, and blowing air on them to make them move — showing a potential to be used for harvesting air flow to produce light. In addition, the team inserted small magnets inside the devices for magnetic steering.
“They are basically maintenance-free,” Cai said. “Once we inject culture solution into the materials, that’s it. As long as they get recharged with sunlight, they can be used over and over again for at least a month. We don’t need to change out the solution or anything. Each device is its own little ecosystem — an engineered living material.”
“When you’re putting living organisms inside a synthetic, enclosed space, you need to think about how to make that space habitable — how it will let air in and out, for example — while still keeping the material properties that you want,” said study First Author Chenghai Li, a Mechanical and Aerospace Engineering Ph.D. student in Cai’s lab.
Li says the key was to make the elastic polymer porous enough for gases like oxygen to pass through without any leakage.
“This is a neat demonstration of using living organisms for an engineering application,” said Latz. “This work continues to advance our understanding of bioluminescent systems from the basic research side while setting the stage for a variety of applications, ranging from biological force sensors to electronics-free robotics and much more.”
Here is an interview (edited for clarity) with Cai.
Tech Briefs: What’s the next step in your research?
Cai: We are trying to integrate the bioluminescent algae into hydrogel matrix to create responsive biohybrid materials, which can then be easily fabricated to different shapes and sizes.
Tech Briefs: When will this technology be commercially available?
Cai: It is very hard to predict. We are still in the stage of proof-of-concept demonstration.
Tech Briefs: Will there be a large market for it?
Cai: We have no idea about it at this point. We are actively seeking novel applications based on our development.
Tech Briefs: How will this further the industry and advance research?
Cai: Our work may enable the development of novel/intelligent robots.
Tech Briefs: Are you working on other such advances? Projects?
Cai: Yes, our ongoing studies are to construct soft robots using the biohybrid approach developed in the current research.
Tech Briefs: Anything else you’d like to add?
Cai: Biohybrid is a recently emerging approach to create novel functionalities. The approach is very promising because we can directly harvest many sophisticated biological functions, which, otherwise, cannot be easily reproduced in the lab.