Hair’s where it’s at

A gypsy moth caterpillar. (CC-BY-SA-3.0 Materialscientist)

Humans have a long and fruitful history of looking towards nature for ideas to build new technologies or solve problems. From Leonardo Da Vinci studying the flight of birds to develop the earliest “flying machines”, to the Swiss engineer George de Mestral developing Velcro after studying the surface of burrs, nature has long been influencing technologies.

A recent review paper published in the journal Smart Materials and Structures takes an in-depth look at the different “hairy” sensors that a whole host of animals possess. This could help us to develop our own sensors to serve a multitude of purposes from gauging flow turbulence to more efficient liquid-dispensing methods to developing robots that can successfully navigate underwater or underground and other biomedical applications. Such sensors would require many capabilities such as short response times and low detection thresholds – capabilities that already exist in animals.

Many life-forms live in conditions that are constantly changing and so have adapted a wide range of sensory strategies to survive. In the paper, the authors point towards many examples. Mexican blind fish rely on a” lateral line system” to detect movement and vibration in the surrounding water. Crickets use their hairy “cerci” or feelers that provide them with flow information that let them know if another creature is approaching them. Caterpillars also use cerci to detect airborne disturbances that let them know when predators, like flying wasps, are overhead. Meanwhile, bats control their flight by monitoring air-flow conditions via hairs on their wings.

According to the paper, “Among the various flow sensors in nature, the instinctive flow sensors of aquatics and arthropods are the most intensively studied.” In the initial sections the researchers look at the “morphology, function and biomechanics of the lateral line neuromas of aquatics and the fusiform hairs of arthropods are examined to shed light on the development of their artificial counterparts”. In later sections they divide the types of sensors that can be developed into six categories: thermal, piezoresistive, capacitive, magnetic, piezoelectric and optical sensors. They look at various groups around the world that are currently developing some of the different types of sensors considered and the different methods they use. The final discussion looks at how to best optimize such sensors, process the information they would provide and how the field will progress in the future.

So for an insightful look into all sensors hairy, take a look at the paper here.