Sea urchin sperm is surprisingly useful to robotics experts
Sperm has a unique sense direction . Many species have reproductive cells that are tuned to find eggs no matter how far or difficult they travel. Sea urchin sex. First, males and women will release sperm and eggs into the ocean. These spiny seabed critters use a chemical bread crumb trail to find and fertilize eggs in open waters. Engineers are using this attraction method to create smarter, more destination-seeking robots.
A study published December 9 in the journal Physical Review E details the similarities between the trajectory of sea urchin sperm and computer systems that use a type of real-time search approach called extremum seeking. To better understand the behavior of the sperm, engineers from the University of California Irvine and University of Michigan created a mathematical model of its pathway. The authors believe that analyzing the biological nature of the sea urchin could help to design miniature robots that can follow the same cues from other sources.
Since the 1920s, engineers have used extremum seeking as an adaptive control technique to program technologies that help steer or direct systems for maximum function. It has been used to optimize fuel flow in flight-propulsion system, combustion for engines and gas furnaces, as well as anti-lock brake systems in cars. At its basics, a system’s extremum seeking algorithm tracks a signal beacon emitted by a source, says Mahmoud Abdelgalil, who studies dynamics and control at UC Irvine and was the lead author of the paper.
When you think about robotic designs, sea-urchin sex might not be the first thing that comes to your mind. Abdelgalil claims that their reproductive cells are a useful and well-studied biologic model .. Sea urchin sperm uses chemotaxis , to locate an egg. This is where cells respond to chemical stimuli. The sperm-activating protein that sea urchin eggs secrete is a compound called a “sperm-activating” peptide. This interacts with the flagellum of the sperm and controls how it beats. This bends and curves the direction of the sperm in order to get to the egg.
“Sperm do not have a GPS,” Abdelgalil said. They don’t know where the egg is at any given time. They measure the local concentration of the peptide at the current location, then they use that information to move in the direction towards increasing concentration levels – which we like to refer to as the direction of the concentration gradient
An extremum-seeking robot doesn’t have any coordinates or other information about its target’s location. All it knows is that it can follow the dynamic signal from its current position. Abdelgalil was inspired to study sea urchin sperm after he saw a paper that described their behavior under a microscope. The trajectory of the sperm was almost identical to that of a proposed model for an extremum-seeking robot. This simple machine can only control its direction and move forward.
” “As soon as i saw the two images, I realized that these are more or less the exact same,” he said. Abdelgalil and colleagues showed in the new study how key components of sea urchin sperm navigation strategy resemble hallmarks of extremum seeking.
This highly effective searching strategy that evolved over time in nature could be used to fine-tune future system designs and technologies. Minimal sensors and extreme seeking algorithms could be used to steer tiny robots such as those being tested for targeted drug delivery. Abdelgalil states that research groups have already looked into drug delivery microrobot designs using external signals. For instance, Abdelgalil mentions that researchers at ETH Zurich in Switzerland developed a tiny starfish larva-inspired robot that is guided by sound waves and might one day be useful in delivering drugs directly to specific diseased cells in the body. He says, “I hope my research will eventually be applied to studying or designing microrobots which employ extremum seeking autonomy to navigate environments and find infected cells that require drugs.”
Abdelgalil also notes that other organisms seem to have some form of extremum seeking, including bacteria searching for food or algae moving in the direction of light. He says that we can learn from these microorganisms’ behavior to design robots that behave in a defined way even when there is no command to do so.
This can improve the autonomy of robots that are more commonly operated.
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