Although dielectric elastomers have been extensively studied recently, to date there has been little research into application of dielectric elastomer actuators to undersea robots. This letter focuses on development of a jellyfish robot using a dielectric elastomer actuator, which exhibits muscle-like properties including large deformation and high energy density. We carry out experiments to test the actuator’s deformation and force. Theoretical simulations are conducted to analyze the performance of the actuator, which are qualitatively consistent with the experiments. The preliminary studies show that this jellyfish robot based on dielectric elastomer technology can move effectively in water. The robot also exhibits fast response and high capacity of payload (compared to its self-weight).

A Soft Jellyfish Robot Driven by a Dielectric Elastomer Actuator

Untethered, controllable, mobile microrobots have been proposed for numerous applications, ranging from micro-manipulation, in vitro tasks (e.g., operation of microscale biological substances) to in vivo applications (e.g., targeted drug delivery; brachytherapy; hyperthermia, etc.), due to their small-scale dimensions and accessibility to tiny and complex environments. Researchers have used different magnetic actuation systems allowing custom-designed workspace and multiple degrees of freedom (DoF) to actuate microrobots with various motion control methods from open-loop pre-programmed control to closed-loop path-following control. This article provides an overview of the magnetic actuation systems and the magnetic actuation-based control methods for microrobots. An overall benchmark on the magnetic actuation system and control method is also discussed according to the applications of microrobots.

/pdf/magnetic-actuation-based-motion-control-for-microrobots-an-2rtj6k5r9o.pdf

Magnetic Actuation Based Motion Control for Microrobots: An Overview

Five unique soft robotic jellyfish were manufactured with eight pneumatic network tentacle actuators extending radially from their centers These jellyfish robots were able to freely swim untethered in the ocean, to steer from side to side, and to swim through orifices more narrow than the nominal diameter of the jellyfish Each of the five jellyfish robots were manufactured with a different composition of body and tentacle actuator Shore hardness A three-factor study was performed with these five jellyfish robots to determine the impact that actuator material Shore hardness, actuation frequency, and tentacle stroke actuation amplitude had upon the measured thrust force It was found that all three of these factors significantly impacted mean thrust force generation, which peaked with a half-stroke actuation amplitude at a frequency of 08 Hz

https://iopscience.iop.org/article/10.1088/1748-3190/aadcb3/pdf

Thrust force characterization of free-swimming soft robotic jellyfish.

Soft robot is a kind of machine form with flexible deformation capability. Making flexible actuators has recently become a hot research topic in the field. In this study, we demonstrated the facile fabrication of a soft electromagnetic actuator using liquid metal coil of Ga-In alloys, and designed several illustrative mechanical devices, such as jellyfish like robot, soft fishtail and flexible manipulator. Measurements of the liquid metal coil’s electrical properties confirmed that the liquid metal coil was mechanically stable under 48% uniaxial strains. Furthermore, the resistance of the liquid metal coil is stable under 60° bending deformation. Tests on the liquid metal coil’s driving properties confirmed that the liquid metal coil (55 mm×55 mm×1 mm) could reach the maximum displacement amplitude of 21.5 mm with the current of 0.48 A. It was shown that the electromagnetic interaction between the magnet and the liquid metal coil enables the coil as a highly efficient actuator. The mechanisms lying behind were interpreted and future applications of such system were discussed.

Liquid metal spiral coil enabled soft electromagnetic actuator

Jellyfish are energy-efficient swimmers due to the muscle-powered flapping of their soft bell that facilitates a unique energy recapture mechanism. In this paper, we present a bio-inspired jellyfish robot named Poly-Saora that mimics the swimming behavior of the jellyfish species Black sea nettle (Chrysaora achlyos). An assembly-based fabrication method is used to create the Poly-Saora that is developed mainly with polymeric materials (95% of the robot by volume). Twisted and coiled polymer (TCP) actuators are successfully implemented in this robot and show great potential for underwater applications. The influence of different parameters such as the amplitude of the input power, the actuation frequency, and the lifecycle of the actuator are investigated underwater. A full characterization of 6-ply TCP muscles is demonstrated. An actuation strain of ~10 % is achieved in water at a frequency of 0.1Hz and 50 kPa load. When integrated into the jellyfish, the TCP was able to bend a single bell by 17˚. Poly-Saora was able to swim a vertical distance of 180 mm in 220 s with four TCP actuators each confined in a separate conduit. The robot mimics the swimming behavior of a real jellyfish by contracting the bell segments through the activation of the actuators, which generates forced water circulation under the bell in a pulsating rhythm, consequently creating a vertical movement of the robot. Overall, Poly-Saora is presenting a model of an underwater system that is driven by stimuli-responsive polymer materials and has unique advantages over conventional rigid robots due to their lightweight, muscle-like structures, silent actuation and ease of manufacturing. This robot can be used for safe interaction with other underwater species and their natural habitats when fully developed.

https://iopscience.iop.org/article/10.1088/1361-665X/ab7738/pdf

Poly-Saora robotic jellyfish: swimming underwater by twisted and coiled polymer actuators

Among the various kinds of actuations for biomimetic robots, the electromagnetic actuation (EMA) method has been regarded as the one with the most potential. This paper proposes a jellyfish-like swimming mini-robot actuated by an EMA system in three-dimensional (3D) space. The jellyfish-like mini-robot has four flexible fins, each of which is equipped with a permanent magnet for electromagnetic actuation; the robot’s body is 17 mm long and 0.5 mm thick. Our EMA system was able to generate a uniform magnetic field in a desired direction in 3D space, which could bend the fins of the jellyfish-like mini-robot. Therefore, a cyclic change in the uniform magnetic field, in the EMA system, would synchronize the fluctuation of the fins and could generate a propulsion force for the robot, in the desired direction. In order to maximize the propulsion force of the jellyfish-like mini-robot, the waveform and frequency of the input current in the EMA system are optimized. Consequently, our jellyfish-like mini-robot was able to generate maximum propulsion force when a square waveform input current (13 A magnitude and 10 Hz frequency) was applied to the EMA system. Finally, the jellyfish-like mini-robot with the EMA system was able to perform various 3D swimming motions.

http://iopscience.iop.org/article/10.1088/0964-1726/21/5/057001/pdf

A jellyfish-like swimming mini-robot actuated by an electromagnetic actuation system

For the actuation of mini-robots, electromagnetic based actuation (EMA) methods were proposed EMA system has many advantages for the wireless actuation of mini-robots This paper introduces our proposed biomimetic swimming mini-robots such as tadpole robot and jellyfish robot The biomimetic swimming mini-robots could be driven by an external alternating magnet field using three pairs of Helmholtz coils The swimming mini-robots consist of a buoyant robot body, permanent magnets, and fins Especially, the tadpole mini-robot has a single fin which is directly linked to the permanent magnet and the jellyfish mini-robot has multiple fins which have a permanent magnet at the end of fin The external alternating magnetic field from three pairs of Helmholtz coils could generate the propulsion and steering force of the tadpole mini-robot and the jellyfish mini-robot in 2- and 3-dimensional (-D) space Firstly, we demonstrated the fabrications of the EMA coil system and the mini-robots Secondly, we summarized the locomotive algorithms of the mini-robots using EMA Thirdly, we setup the control system for the EMA driven mini-robots, which consists of EMA coils, dual cameras, controller, power amplifier, and conventional joystick Through various experiments, we evaluated the locomotion algorithms the swimming mini-robots using EMA system Finally, we demonstrated the performances of the swimming mini-robots in 2-D and 3-D space

Biomimetic swimming mini-robots using electro-magnetic actuation (EMA) system

As demands of microrobots in medical applications increases, micro-actuators for the microrobots are actively studied. However, miniaturized motors cannot be easily applied to microrobots owing to the limitations of their sizes and generating forces. Therefore, a new functional smart material for microrobots should be developed. Among various smart materials, we focused on a ferro-actuator using ferrofluid. The ferro-actuator is regarded as a smart material and can show large displacements, excellent repetition performances, and relative small actuation forces. In this paper, a cellulose is used to make a paper backbone membrane because it has superior properties compared with any others conventional papers. The cellulose paper backbone membrane is easily fabricated as complex shapes and shows a large displacement in a magnetic field. In detail, patterned ferropaper actuator is made of cellulose acetate using general MEMS procedure and PDMS molding method. Finally, through bending experiments and alignment experiments of the fabricated ferropaper actuator using an electromagnetic actuation (EMA) system, the patterned ferropaper actuator was characterized.

Youngho Ko

Papers

A jellyfish-like swimming mini-robot actuated by an electromagnetic actuation system

Biomimetic swimming mini-robots using electro-magnetic actuation (EMA) system

Characteristics of Patterned Ferropaper Actuator based on Cellulose using Electromagnetic Actuation System