This study describes the enhancement of a vacuum actuated soft gripper's grasping capabilities using retractable finger nails and an active re-configurable palm. The finger nail mechanism is pneumatically actuated and enables the gripper to perform complex grasping and manipulation tasks with high repeatability. The retracted nails can exert normal grasping forces of up to 1.8N and enable grasping of objects up to 200μm thick from flat surfaces, while allowing the gripper to execute delicate pinch grasps without complex trajectory or grasp planning. A wide array of robotic grasping tasks that were not possible without nails are also described.

In this paper, the design, fabrication, numerical studies, and preliminary characterization of a multi-fin soft robot are presented. The design is simple, robust, and fully autonomous. The robot has a 216mm body length and displays great potential to achieve uncoupled surge (forwards and backwards), sway, and heave motions. Computational fluid dynamic (CFD) studies are employed to evaluate appropriate fin control approaches and their influence on force generation. By using asymmetric input functions to actuate all fins in phase, the robot can achieve close to pure heave motions while single fin symmetric actuation enables forwards, backwards, and sway motions.

In this study, a single-step additive manufacturing approach to fabricate an array of bio-inspired soft whisker-like sensors is presented. Each whisker is a damped oscillator system that is tuned to a different resonant frequency whose response is characterized through experimentation in an air medium. A 3 × 1 polymer based whisker-array is used to distinguish individual frequency components in mixed-frequency signals, achieving a form of “mechanical Fourier transform”.

Batoids use their large pectoral fins to achieve unique maneuverability and propulsive performance. In this work, the design, fabrication and characterization a soft batoid-like robot is presented. The robot is designed to mimic un-dulatory rajiform locomotion. The design is under-actuated, simple and robust and well suited for propulsive performance experiments thanks to its full autonomy, long battery life, and wireless recharging capabilities. The robot has a 180mm body length, a maximum flapping amplitude of 60deg, and reaches a peak speed of 0.93 body length per second. In order to characterize its swimming kinematics and propulsive forces a special setup was built using an instrumented holder and high speed video. Experiments were conducted to characterize propulsive force generation with varying fin flapping frequencies (from 1hz to 2. 4hz), amplitudes, and wavelengths. The results show that while both flapping frequency and amplitude influence propulsive forces, for the locomotion modes tested, flapping frequency has a stronger effect on both thrust and side forces. Furthermore, larger side forces than thrust forces are produced for the same swimming parameters.

This paper details the design and characterization of a biomimetic flapping actuator inspired by fin-rays of fishes. The flapper design consists of two carbon fiber beams with a thin viscoelastic material sandwiched between them. When the beams are actuated to move relative to each other tangentially, the entire assembly curves out of the plane of symmetry creating a flapping motion. A model for the mechanism is presented, and the model's predictions for flapper deformation and energy consumption are verified with experiments. A closed-form solution is presented for the case of a static flapper with uniform properties along its length. The model is a powerful tool to predict the response of the flapper to changes in material parameters or dimensions. A flapper with varying dimensions along its length is also characterized experimentally, and compared with a uniform flapper.

Pinnipeds (seals, sea lions, etc.) use their whiskers to find and track hydrodynamic trails left by potential prey. Our group recently developed new underwater sensors based on pinniped whiskers, which not only exploit their characteristic geometries but also the dynamics of whisker follicles to improve and tailor sensing capabilities. The sensors are simple, robust, and a straightforward methodology can be used to tailor their sensitivity to different target signals. A lumped parameter model is used to predict sensor performance. The model predictions for static scenarios are compared to experimental results for constant speed measurements. Scalings for static and dynamic measurement scenarios are also given. In both cases the sensors show a strong sensitivity to follicle material properties and whisker length. The results show the sensors can be used for flow sensing and are a promising feedback source for navigation based on near field hydrodynamic features.

This paper outlines the design of a portable manipulator system for use in remote detection and care of hemorrhage using High Intensity Focused Ultrasound (HIFU). We have developed a kinematically redundant manipulator that uses high fidelity force control for safe interaction with human patients. The manipulator is outfitted with a dual imaging and sonication end-effector for hemorrhage detection and treatment. Unlike most available force controlled manipulators, the design presented in this paper has all the actuation embedded inside its body eliminating the need for a base which greatly improves portability. We review the main design features, advantages, and trade-offs of this approach and present experimental data of hemorrhage detection and controlled sonication of biological tissue samples.

The maneuvering performance of a robotic device designed to mimic the swimming motions of Thunniform swimmers is presented. In contrast to existing designs, this design achieves fish like locomotion through the use of a single actuator and a compliant body and tail. Experiments were performed using both biased swimming motions and coasted turns. During these experiments the Compliant Robotic Tuna (CRT) achieved steady swimming speeds of up to 0.37 body lengths/second, average turning rates of up to 12.6 degrees per second, and turning radii as low as 1 body length. In addition, this paper compares the measured maneuvering performance with the predictions of a simplified rigid body model that was derived using both theoretical and empirical techniques. The swimming motions studied in this paper were achieved using open loop mechanisms. Therefore the potential for performance improvements exists.

The self-propelled swimming performance of two prototypes designed to mimic the kinematics of real fish swimming at high Reynolds numbers is presented. The design methodology uses structural compliance instead of discrete assemblies to achieve desired kinematics. Experiments took place at Reynolds numbers between 15×103 and 90×103. A prototype with a thick peduncle, low aspect ratio caudal fin, and uniform material distribution throughout its flexible tail, reached a maximum forward velocity of 0.11ms− 1 that coincided with a maximum thrust of 0.2N. A second prototype with a thin peduncle, high aspect ratio caudal fin, and nonuniform material distribution throughout its tail, reached a maximum forward velocity of 0.31ms− 1 that coincided with a maximum thrust close to 0.11N. Peak velocities and thrusts occured at driving frequencies between 2.7Hz and 3.5Hz for the type of kinematics used, and corresponded to Strouhal numbers close to 1.75 and 0.8 respectively. Mechanism motions were achieved in open loop, hence improvements can be made by implementing closed loop control to correct errors in desired kinematics. Finally, this study shows that simpler, more robust mechanisms, as the ones accomplished with our new design methodology, can display similar or better performance than the state of the art.