Tails serve various functions in both robotics and biology, including expression, grasping, and defense. The vertebrate tails associated with these functions exhibit diverse patterns of vertebral lengths, but the precise mechanisms linking form to function have not yet been established. Vertebrate tails are complex musculoskeletal structures, making both direct experimentation and computational modeling challenging. This paper presents Tendon-Actuated Linked-Element (TALE), a modular robotic test bed to explore how tail morphology influences function. By varying 3D printed bones, silicone joints, and tendon configurations, TALE can match the morphology of extant, extinct, and even theoretical tails. We first characterized the stiffness of our joint design empirically and in simulation before testing the hypothesis that tails with different vertebral proportions curve differently. We then compared the maximum bending state of two common vertebrate proportions and one theoretical morphology. Uniform bending of joints with different vertebral proportions led to substantial differences in the location of the tail tip, suggesting a significant influence on overall tail function. Future studies can introduce more complex morphologies to establish the mechanisms of diverse tail functions. With this foundational knowledge, we will isolate the key features underlying tail function to inform the design for robotic tails. Images and videos can be found on TALE's project page: https://www.embirlab.com/tale.

Researchers from Keio University in Japan have created a prototype for a mechanical tail that they say -- not unlike a real, biological tail -- provides the wearer more agility and balance. The tail, dubbed The Arque tail, was presented at conference in Los Angeles last week that brings together emerging technologies in gaming and graphics, Fast Company reports. Arque can augment a wearer's agility by acting as a a counterbalance that shifts weight While a human with a tail may evoke our primate ancestry, researchers say that their version -- a swiveling worm-like device strapped around a user's waist -- is inspired by the Seahorse. Seahorse tails, notes Fast Company, are strong enough to endure attacks from predators but still flexible enough to be used a type of hand that can grip coral and other environmental objects. For proof of a tail's efficacy in helping to gracefully navigate narrow or tenuous landscapes, one might look to the acumen of more domestic animals, like cats.

A group of researchers from Keio University in Japan has created a robotic tail for humans. Called Arque, the robotic tail prototype was designed to do what a real tail does: balance out the rest of the body. The researchers, who are part of Keio's graduate school of media design, presented the work last week at the 2019 SIGGRAPH conference in Los Angeles, which focuses on graphics, gaming, and emerging technology. The appendage was inspired by a seahorse's tail, which is strong enough to withstand predators' bites but still flexible to grip things in its environment, like coral. The researchers' prototype was also designed to fit whoever ends up wearing it: the tail can be adjusted to the wearer's body by adding or removing modular "vertebrae."