An image from The Economist article is above. Clearly in submarine, UUV, AUV, seabed or harbour defense applications, "whisker" sensors may be useful to detect unnatural water flows. This may particularly be regular propeller movement vortices. "Whiskers" may be most useful in places like the Baltic Sea, where AIP is frequently used by Sweden and Germany, to minimize passive sonar detectable diesel emissions.
Whiskers are so prominent and regular on seals that they must be very valuable in detecting fish movement in totally opaque (eg. muddy) and low or no light environments.
So I located a 3DPRINT.COM article of January 17, 2018. The following is an abridged version which begins:
“3D Printed Sensor Mimics Seal Whiskers to Detect Underwater Vortices
The word pinniped refers to semi-aquatic fin- or flipper-footed mammals, including to seals, sea lions and walruses. These creatures also have whiskers, which...serve an important purpose – they help the pinnipeds track their prey underwater by sensing the vortices left behind by the movement of said prey. A group of researchers in the Department of Mechatronics Engineering at in South Korea believe that a sensor based on the pinnipeds’ method of hunting could be valuable for soft robotics and underwater exploration, [Pete Comment: And to detect submarine and AUV water movement] they set out to create one using 3D printing.
The research was described in a paper entitled “Fully 3D Printed Multi-Material Soft Bio-Inspired Whisker Sensor for Underwater-Induced Vortex Detection,” which you can read ...” The artificial whisker was 3D printed with polyurethane as well as graphene, which was printed in four patterns using a multi-head 3D printer.
“The four graphene patterns (90° apart) on the polyurethane cylinder enable the flow detection in all directions (0–360°). The length and diameter of the polyurethane cylinder and graphene patterns are 160 × 8 mm and 60 × 0.3 mm, respectively,” the researchers explain. “The conductivity of the printed graphene pattern is 0.6 Ω-cm. With a maximum deformation distance of 5 mm in any direction (0–360°), a substantial change in resistance is observed (from 5.09 × 10 to 6.03 × 10 Ω). The change in resistance in four directions (up, down, left, and right) is studied in an underwater environment.”
“.. The dual-extruder 3D printer was used to print the sensor itself, using the first head, out of polyurethane purchased from , while the second head printed the graphene patterns from filament bought from . After printing was complete, the base and the patterns were connected using copper tape. Copper tape was also used to solder signal wires, and a final 1mm water protection polyurethane layer was dip coated and cured with UV light.
The researchers then tested the sensors, using them to detect the vortices by digitizing the analog signals that indicate resistance changes and sending them to a microcontroller. They concluded that the design and fabrication of the whisker sensor is simple, quick, low cost, and easily deployable in commercial applications, as well as delivering good sensitivity and mechanical reliability. Some further development is needed; however, the study was overall a successful one...
Authors of the paper include Jahan Zeb Gul, Kim Young Su, and Kyung Hyun Choi.”
SEE WHOLE 3DPRINT.COM ARTICLE WHICH HAS DIAGRAMS
In 2015 Dr. Heather Beem explained the mechanics of artificial whiskers.