Although members of the fish species Astyanax fasciatus cannot see, they sense their environment and the movement of water around them with gel-covered hairs that extend from their bodies. Their ability to detect underwater objects and navigate through their lightless environment inspired a group of researchers to mimic the hairs of these blind cavefish in the laboratory.
While the fish use these hairs to detect obstacles, avoid predators and localize prey, researchers believe the engineered sensors they are developing could have a variety of underwater applications, such as port security, surveillance, early tsunami detection, autonomous oil rig inspection, autonomous underwater vehicle navigation, and marine research.
"These hair cells are like well-engineered mechanical sensors, similar to those that we use for balance and hearing in the human ear, where the deflection of the jelly-encapsulated hair cell measures important flow information," said Vladimir Tsukruk, a professor in the Georgia Tech School of Materials Science and Engineering. "The hairs are better than active sonar, which requires a lot of space, sends out strong acoustic signals that can have a detrimental effect on the environment, and is inappropriate for stealth applications."
In a presentation on March 20 at the American Physical Society meeting, researchers from Georgia Tech described their engineered motion detector that mimics the underwater flow measurements made by the blind cavefish. This research was sponsored by the Defense Advanced Research Projects Agency (DARPA).
Tsukruk and graduate students Michael McConney and Kyle Anderson conducted preliminary experiments with a simple artificial hair cell microsensor made of SU-8, a common epoxy-based polymer capable of solidifying, and built with conventional CMOS microfabrication technology. They found that the cell by itself could not achieve the high sensitivity or long-range detection of hydrodynamic disturbances created by moving or stationary bodies in a flow field. The hair cell needed the gel-like capsule – called the cupula – to overcome these challenges.
"After covering the hair cell with synthetic cupula, our bio-inspired microsensor had the ability to detect flow better than the blind fish. The fish can detect flow slower than 100 micrometers per second, but our system demonstrated flow detection of several micrometers per second," said Tsukruk, who also holds an appointment in Georgia Tech's School of Polymer, Textile and Fiber Engineering. "Adding the cupula allowed us to detect a much smaller amount of flow and expand the dynamic range because it suppressed the background noise."
In addition, the hydrogel encapsulation protects the sensors and increases their ability to withstand deformation due to impact. It also helps the hairs better withstand the marine environment by resisting corrosion and microorganism growth.Before the research team began synthesizing the gel-like material in the laboratory, they used optical microscopy and confocal fluorescence microscopy to determine the size, shape and properties of real cavefish cupula. One type of cupula they found was cylindrical-shaped, with a height approximately five times larger than its diameter. The tallest part of the cupula was far enough away from the surface that it was exposed to free-flowing water and could bend with the hair to detect changes in flow.
"This method of adding one droplet at a time allowed us to control the width and height of the cupula and the distance from the bottom of the cupula to the base of the hair," said McConney.
While the researchers found that placing the synthetic cupula closest to the sensor platform enhanced the durability and lifetime of the capsule, they captured the best flow measurements when the cupula structure started halfway up the hair and extended past the hair by 50 percent.
They achieved the best flow results with fabricated hairs that were 550 micrometers long with dried cupula that started 275 micrometers above the base of the hair and extended 275 micrometers above the hair, giving the total hair-cupula structure a height of 825 micrometers.
To date, the researchers have fabricated an array of eight microsensors and shown that the array is able to detect an oscillating object underwater. They are currently looking for industrial partners to efficiently scale-up the research by fabricating arrays of thousands of these sensors and testing them in real marine environments.
Abby Vogel | EurekAlert!
Further reports about: > Astyanax fasciatus > Ferchau Engineering > active sonar > autonomous underwater vehicle navigation > blind cavefish > early tsunami detection > flow measurement > flow sensors > gel-covered hairs > hair structures > jelly-encapsulated hair cell > lightless environment > marine environment > marine research > movement of water > port security > sensing motion > surveillance > underwater objects
Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie
Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
20.02.2017 | Materials Sciences
20.02.2017 | Health and Medicine
20.02.2017 | Health and Medicine