Soft robotic hands and grippers are increasingly attracting attention as robotic end effectors. Compared with their rigid counterparts, they are safer for human-robot and environment-robot interactions, easier to control, and more compliant, and they cost and weigh less. Design studies of soft robotic hands have focused mostly on the soft fingers and bending actuators. However, the palm is also an essential part in grasping. In this work, we propose a novel design for an inexpensive soft humanoid hand with pneumatic soft fingers and a soft palm. The configuration of the soft palm is based on a modular design that can be applied to actuate different kinds of existing soft fingers. The splaying of the fingers, bending of the whole palm, and abduction and adduction of the thumb are implemented by the palm. Moreover, we present a new design of soft finger, called the hybrid-bending soft finger (HBSF), that can both bend in the grasping axis and deflect in the side-to-side axis, achieving human-like motion (Figure 1). The functions of the HBSF and soft palm are evaluated both in simulation, using the Simulation Open Framework Architecture (SOFA) framework, and experimentally. Six finger designs with 1-11 longitudinal segments are analyzed. The versatility of the soft hand is evaluated and demonstrated experimentally by its grasping of objects according to Feix's taxonomy. The results demonstrate a great diversity of grasps, with 31 of the 33 grasp types of the taxonomy performed successfully with the proposed design, showing promise for grasping a large variety of objects with different shapes and weights.

Soft robotics shows considerable promise for various underwater applications. Soft grippers as end-effectors are particularly useful for compliant and robust grasping compared to rigid mechanisms. In this work, we describe the design, fabrication and operation of a soft robotic hand driven by water hydraulics for underwater grasping. The proposed design has, in addition to the five fingers of a human hand, an extra soft thumb arranged symmetrically in an active soft palm. The soft fingers are designed with four chambers to enable bidirectional bending and deflection motions. We propose a novel elastic fiber reinforced structure to enhance and constrain the flexion movements of three palm actuators. The versatility of the underwater robotic hand is evaluated by implementing the human grasping gestures of the Feix taxonomy. Furthermore, we present a low-cost one-camera-multiple-mirrors imaging approach for capturing the grasps from multiple viewpoints simultaneously.

Animals and plants have numerous active protections for adapting to the complex and severe living environments, providing endless inspiration for extending the service life of materials and machines. Conch, a marine animal living near the coast and chronically suffering from the erosion of sand in water, has adapted to the condition through its anti-erosion conch shell. Romanesco broccoli, a plant whose inflorescence is self-similar in character, has a natural fractal bud’s form. Coupling the convex domes on the conch shell and the fractal structure of Romanesco broccoli, a novel valve core structure of a water hydraulic valve was designed in this paper to improve the particle erosion resistance and valve core’s service life. Three models were built to compare the effect among the normal structure, bionic structure, and multi-source coupling bionic structures, and were coined using 3D printing technology. A 3D printed water hydraulic valve was manufactured to simulate the working condition of a valve core under sand erosion in water flow, and capture the experimental videos of the two-phase flow. Furthermore, based on the water hydraulic platform and one-camera-six-mirror 3D imaging subsystem, the experiment system was established and used to compare the performance of the three different valve cores. As a result, the results showed that the coupling bionic structure could effectively improve the anti-erosion property of the valve core and protect the sealing face on the valve core from wear. This paper presents a novel way of combining advantages from both animal (function bionic) and plant (shape bionic) in one component design.

Water hydraulics relief valves are essential components of hydraulic systems. These valves maintain the desired pressure and thereby prevent other components from being damaged. During operation of the relief valve, the water flow often cavitates in the valve port owing to the rapid decline in pressure, affecting the stability and safety of the hydraulic system. To improve relief valve performance, an optimal design of the valve was determined. Using a computational fluid dynamics approach, the effects of the valve core design and the nonsmooth groove structure of the valve seat on the jet flow structure were modeled and tested. The anti-cavitation structure was optimized parametrically, and the ideal valve port structure was determined. Tests were conducted to compare cavitation in the water hydraulics relief valve with and without the anti-cavitation structures. Results of these tests showed evident enhancement of cavitation performance.

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr₂O₃, Al₂O₃, T_i2O₃. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al₂O₃ cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies.

Soft robots apply compliant materials to perform motions and behaviors not typically achievable by rigid robots. An underwater, compliant, multi-segment continuum manipulator that can bend, swallow, disgorge is developed in this study. The manipulator is driven by McKibben water hydraulic artificial muscle (WHAM). The mechanical properties of the WHAM are tested and analyzed experimentally. The kinematics model, which concerns about the variable diameter structure of the soft grippers, are established to simulate the behaviors of the manipulator among the bending, swallowing and disgorging procedure. A mouth-tongue collaborative soft robot assembled with another single-segment soft robot arm is presented. And its functions are experimentally testified. The distinctive functions were verified according to the experimental results.