Whiskers are a fantastic natural sensor that enables cats, fish, seals, and many other animals to detect not just direct contact but even air flow indicating an approaching object. In a fascinating example of biomimicry, University of Queensland engineer Pauline Pounds and her colleagues have developed tiny whisker sensors for drones. According to the researchers, the whiskers are well-suited for "navigating through dark, dusty, smoky, cramped spaces, or gusty, turbulent environments with micro-scale aircraft that cannot mount heavier sensors such as lidars." At IEEE Spectrum, Evan Ackerman writes:
The whisker fibers themselves are easy to fabricate—they’re just blobs of ABS plastic that are heated up and then drawn out into long thin fibers like taffy. The length and thickness of the whiskers can be modulated by adjusting the temperature and draw speed. The ABS blob at the base of each whisker is glued to a 3D-printed load plate, which is in turn attached to a triangular arrangement of force pads (actually encapsulated MEMS barometers)...
It can detect forces as low as 3.33 micronewtons, meaning that the researchers had to be careful not to stand too close to the whiskers while making measurements since the force of their breathing would throw things off. This sensitivity allows the whiskers to detect the wave of air generated by objects moving towards them, perhaps not in time for the drone to actually stop, but certainly in time for it to take other steps to protect itself, like cutting power to its motors. The whiskers can also be used to measure fluid flow (a proxy for velocity through the air), and of course, at slow speeds they work as contact sensors.
"Sensitive Whiskers Could Make Small Drones Safer" (IEEE Spectrum)