An elephant’s trunk is an extraordinary tool that combines immense power with remarkable dexterity. With its muscular, boneless structure, an elephant can deftly peel a banana or pick a peanut from its shell.
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According to a paper published in the journal PNAS Nexus, studies of the trunk's powerful, flexible and sensitive properties could provide scientists with data to feed into the next generation of advanced soft robotics.
Lucia Beccai, from the Istituto Italiano di Tecnologia (IIT), and colleagues obtained a trunk from a single adult Asian elephant (Elephas maximus) that died of natural causes at Zurich Zoo, Switzerland, in 2020.
The authors evaluated 35 samples across the specimen using biomechanical testing, histology and a suite of imaging techniques, along with computational modelling.
Their findings revealed that the trunk’s skin is not homogeneous, but has a stark dichotomy. The dorsal skin operates like a tough yet sensitive, armour-like shield which is 3.14 times stiffer than the underside. The ventral skin, by contrast, is a highly flexible, sensitive surface for grasping.
The low stiffness of the ventral skin allows it to conform to objects, maximising contact area and forming a steady grip. Beneath the surface of the trunk’s ventral skin are dome-shaped dermal papillae.
The future of robotics
Specialist modelling shows that these structures act like a subsurface mechanical lens, concentrating and amplifying mechanical stress where sensory nerves are located.
The researchers found that the trunk combines protection and sensitivity in a way that could be useful for robotics. Engineers may be able to use similar designs to build robotic grippers that can sense light touches without damaging delicate sensors.
