Recurrent Braiding of Thin McKibben Muscles to Overcome Their Limitation of Contraction.

This study presents a novel idea of rebraiding thin McKibben muscles to overcome their limitation of contraction. The thin McKibben muscles, presented in the authors' previous work, have the flexibility that allows them to be braided. According to the experimental results of our previous research, the original single muscles have a contracting ratio of 28%, and the corresponding value for the muscles braided once is 37%. In this research, we achieved 41% contraction of thin McKibben muscles by braiding twice. The contraction ratio increases if the muscles are braided more. They will then overcome their limitation of contraction. In this report, several prototypes of muscles with different braiding times are designed, fabricated, modeled, and tested. As a result, the increase in the contraction ratio was confirmed from both a theoretical and an experimental point of view; the results were promising. We believe that recurrent-braided thin McKibben muscles will considerably help improve and develop various soft robotic applications in cases where a high contraction ratio is required.

Active Textile Braided in Three Strands with Thin McKibben Muscle.

This article presents an active textile braided in three strands with thin McKibben muscle. The fabrication of a textile using thin McKibben muscle as thread can be accomplished using a unique braiding method, developed in this study, to provide an active textile that shrinks along the transverse surface direction. This textile-type actuator is suitable as a type of soft robotic actuator for application in wearable robots and musculoskeletal robots because it is extremely lightweight, flexible, and easily applied to robot structures. In this article, the design and characteristics of a braided muscle in three strands, acting as the basic component of an active textile, as well as the design and static characteristics of the active textile, are presented. In addition, theoretical models are proposed for the active textile, and their theoretical characteristics are accordingly derived. The static characteristics of active textiles woven using various design parameters were then evaluated through experiments and modeling. The active textiles were found, both theoretically and experimentally, to provide a greater contraction ratio than a single muscle strand.

A Modular Soft Robotic Wrist for Underwater Manipulation.

This article presents the development of modular soft robotic wrist joint mechanisms for delicate and precise manipulation in the harsh deep-sea environment. The wrist consists of a rotary module and bending module, which can be combined with other actuators as part of a complete manipulator system. These mechanisms are part of a suite of soft robotic actuators being developed for deep-sea manipulation via submersibles and remotely operated vehicles, and are designed to be powered hydraulically with seawater. The wrist joint mechanisms can also be activated with pneumatic pressure for terrestrial-based applications, such as automated assembly and robotic locomotion. Here we report the development and characterization of a suite of rotary and bending modules by varying fiber number and silicone hardness. Performance of the complete soft robotic wrist is demonstrated in normal atmospheric conditions using both pneumatic and hydraulic pressures for actuation and under high ambient hydrostatic pressures equivalent to those found at least 2300 m deep in the ocean. This rugged modular wrist holds the potential to be utilized at full ocean depths (>10,000 m) and is a step forward in the development of jointed underwater soft robotic arms.

A Dexterous, Glove-Based Teleoperable Low-Power Soft Robotic Arm for Delicate Deep-Sea Biological Exploration.

Modern marine biologists seeking to study or interact with deep-sea organisms are confronted with few options beyond industrial robotic arms, claws, and suction samplers. This limits biological interactions to a subset of "rugged" and mostly immotile fauna. As the deep sea is one of the most biologically diverse and least studied ecosystems on the planet, there is much room for innovation in facilitating delicate interactions with a multitude of organisms. The biodiversity and physiology of shallow marine systems, such as coral reefs, are common study targets due to the easier nature of access; SCUBA diving allows for in situ delicate human interactions. Beyond the range of technical SCUBA (~150 m), the ability to achieve the same level of human dexterity using robotic systems becomes critically important. The deep ocean is navigated primarily by manned submersibles or remotely operated vehicles, which currently offer few options for delicate manipulation. Here we present results in developing a soft robotic manipulator for deep-sea biological sampling. This low-power glove-controlled soft robot was designed with the future marine biologist in mind, where science can be conducted at a comparable or better means than via a human diver and at depths well beyond the limits of SCUBA. The technology relies on compliant materials that are matched with the soft and fragile nature of marine organisms, and uses seawater as the working fluid. Actuators are driven by a custom proportional-control hydraulic engine that requires less than 50 W of electrical power, making it suitable for battery-powered operation. A wearable glove master allows for intuitive control of the arm. The manipulator system has been successfully operated in depths exceeding 2300 m (3500 psi) and has been field-tested onboard a manned submersible and unmanned remotely operated vehicles. The design, development, testing, and field trials of the soft manipulator is placed in context with existing systems and we offer suggestions for future work based on these findings.