Tails are used throughout the animal kingdom to help with balance or to grip objects. Humans don't have such a thing, so scientists at the Keio University Graduate School of Media Design have built one to improve the agility of wearers.

There are of course animated robotic tails already manufactured, mostly for cosplay purposes, but the Arque wearable from Junichi Nabeshima, MHD Yamen Saraiji and Kouta Minamizawa is designed for more serious applications.

Inspired by the structure of the grippy, curly end of a seahorse, the prosthetic tail is made up of spring-loaded joints that form connected vertebrae, with pneumatic artificial muscles running through the cavity catering for movement.

The prototype is 71 cm (28 in) long and 11.5 cm (4.5 in) wide, and weighs 1.6 kg (3.5 lb), but the design allows for longer or shorter tails to be created. An air compressor is used to actuate the muscles, which results in movement in eight different directions. This means that it's not yet a stand-alone device, but could be made so in the future as technology improves.

With the Arque, a wearer's center of gravity could be altered by swinging the tail, in much the same way as a monkey jumping from one branch to another might use its tail to adjust balance mid-flight. A body tracker worn on the upper body of the user estimates the center of gravity and the tail is positioned accordingly. This could improve overall agility, or perhaps help the infirm to be more mobile.

The team says that the tail could also provide more realistic full body haptic feedback for folks in a virtual reality environment, to alter their balance to better match what's happening in the virtual world, such as walking in strong winds for example.

The project was recently presented at SIGGRAPH 2019, and a paper is available to view online. The video below has more.