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Dielectric elastomers are soft actuation materials with promising applications in robotics and biomedical de- vices. In this paper, a bio-inspired artificial muscle actuator with artificial tendons is developed for robotic arm applications. The actuator uses dielectric elastomer as artificial muscle and functionalized carbon fibers as artificial te...
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... a diaphragm actuator (shown in Fig. 2) was built to test the carbon fibers' conductivity and characterize the DE material's working performance. The VHB tape was pre-stretched by about 30%. Both sides of the tape were pasted with carbon black. Two clusters of carbon fibers were attached on each side of the actuator by sticky tape. A calibration weight was put on its center ...
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... Many researchers have spent intensive effort on DE actuators, from theoretical modeling to analysis of DE materials [11,13]. Ye et al have developed an artificial muscle and tendon structure using DE material and carbon fibers [14][15][16], and they investigated nano coating technology for DE material [17]. The unique features of DE material make it possible to use them in different fields. ...
... The chosen material and fabrication method were adjusted from former research work [15][16][17]. The design of the diaphragm actuator is shown in figure 2. A 1.5875 mm thick, 152.4 152.4 mḿ birch-wood plate was used for making a wood frame. ...
Human pulse signal tracking is an emerging technology that is needed in traditional Chinese medicine. However, soft actuation with multi-frequency tracking capability is needed for tracking human pulse signal. Dielectric elastomer (DE) is one type of soft actuating that has great potential in human pulse signal tracking. In this paper, a DE diaphragm actuator was designed and fabricated to track human pulse pressure signal. A physics-based and control-oriented model has been developed to capture the dynamic behavior of DE diaphragm actuator. Using the physical model, an H-infinity robust control was designed for the actuator to reject high-frequency sensing noises and disturbances. The robust control was then implemented in real-time to track a multi-frequency signal, which verified the tracking capability and robustness of the control system. In the human pulse signal tracking test, a human pulse signal was measured at the City University of Hong Kong and then was tracked using DE actuator at Wichita State University in the US. Experimental results have verified that the DE actuator with its robust control is capable of tracking human pulse signal.
... Illustration of artificial muscles in robotic arm application[39]. ...
In this paper, a novel artificial muscle/tendon structure is developed for achieving bio-inspired actuation and self-sensing. The hybrid structure consists of a dielectric elastomer (DE) material connected with carbon fibers, which incorporates the built-in sensing and actuation capability of DE and mechanical, electrical interfacing capability of carbon fibers. DEs are light weight artificial muscles that can generate compliant actuation with low power consumption. Carbon fibers act as artificial tendon due to their high electro-conductivity and mechanical strength. PDMS material is used to electrically and mechanically connect the carbon fibers with the DE material. A strip actuator was fabricated to verify the structure design and characterize its actuation and sensing capabilities. A 3M VHB 4905 tape was used as the DE material. To make compliant electrodes on the VHB tape, carbon black was sprayed on the surface of VHB tape. To join the carbon fibers to the VHB tape, PDMS was used as bonding material. Experiments have been conducted to characterize the actuation and sensing capabilities. The actuation tests have shown that the energy efficiency of artificial muscle can reach up to 0.7% and the strain can reach up to 1%. The sensing tests have verified that the structure is capable of self-sensing through the electrical impedance measurement.
Dielectric elastomers are among the soft active materials that may achieve substantial actuation strains when subjected to a high electric field. The material behavior of such elastomers is greatly influenced by environmental humidity. In this paper, we extend upon our previous dynamic modeling frameworks (Khurana et al. in Nonlinear Dyn 104(2):1227–1251, 2021, Sharma and Joglekar in Comput Methods Appl Mech Eng 344:402–420, 2019) to incorporate the effect of humidity in the material model and investigate its effect on the dynamic electromechanical behavior of a transversely isotropic dielectric viscoelastomer actuator with entangled polymer chains. The governing dynamic equation is developed using the non-conservative Euler–Lagrange equation. The proposed model is used for building insights into the effect of membrane humidity on the dynamic behavior and pull-in instability phenomena of the viscoelastomer actuator over a feasible range of anisotropy and entanglement parameters. The results indicate that dielectric elastomer actuators with higher humidity levels have a higher level of deformation and lower electric field at the pull-in point in the DC dynamic mode of actuation, indicating a favorable impact of material humidity. The reduction of critical electric field due to humidity changes can be minimized by integrating the material anisotropy as per the tropical humidity condition. In addition, the Poincaré maps and phase portraits are also plotted to assess the stability, periodicity of the response as well as resonant behavior of the actuator. It is inferred that the higher humidity level of entangled polymer chains diminishes the resonance excitation frequency, which can be further tuned by incorporating material anisotropy. In general, the current study provides initial steps toward the modern actuator designs taking into account the combined effect of humidity conditions, entanglement, and the anisotropic nature of the membrane, which can be effectively implemented for various futuristic applications in the engineering and medical field.
Binding two separate elastomeric substrates is of great importance for the fabrication of next generation stretchable devices including epidermal electronics and soft robotics. However, it is still extremely challenging to find an adhesive to bind arbitrary elastomers with excellent adhesion strength and reliability without compromising the stretchability of the laminated elastomeric substrates. In this study, a sub-micron-thick (∼500 nm) stretchable adhesive was synthesized by using a vapor-phase deposition method. The stretchable adhesive consists of a copolymer film containing curable epoxy and hydroxyl functionalities with sufficiently low glass transition temperature (Tg) in order to render the adhesive elastomeric. Moreover, depositing the adhesive layer in vapor phase induced an interpenetrating polymer network (IPN) at the interface between the elastomeric substrate and stretchable adhesive layer, which enabled strong binding between arbitrary elastomeric substrates such as polydimethylsiloxane (PDMS), Silbione™, 3M VHB™, and Ecoflex™, with substantially enhanced adhesion stability and high transparency. The adhesion strength was fully retained even after more than 10⁵ times of repeated stretch-release cycles of 50% strain. The IPN-induced stretchable but ultrathin adhesive layer developed in this study will serve as a platform bonding technology for the wide range of soft matter engineering applications.
In optical systems, reflectors are commonly used for directing light beams to desired directions. In this paper, a dielectric elastomer based optical manipulator is developed for 2 degree-of-freedom (2-DOF) manipulation. The DE manipulator consists of a diaphragm with four segments which are controlled in two pairs thus generate 2-DOF tilting motions. Due to its soft and gear-less moving structure, the DE manipulator is light-weight and naturally resistant to mechanical vibrations. Moreover, its non-electromagnetic driven mechanism allows it to work under the environments that are exposed to strong magnetic fields. To design a robust control strategy for the actuator, a physics-based and control-oriented nonlinear model is then developed and linearized around equilibrium point. A feedback control system, which consists of two H-infinity controls, is developed to track two tilting angles along two axes. Experimental results have shown that this manipulator is able to track 0.3 degree 2-DOF tilting angle with 0.03 degree accuracy.
Dielectric elastomers (DEs) have significant applications in artificial muscle and other biomedical equipment and device fabrications. Metallic thin films by thin film transfer and sputter coating techniques can provide conductive surfaces on the DE samples, and can be used as electrodes for the actuators and other biomedical sensing devices. In the present study, 3M VHB 4910 tape was used as a DE for the coating and electrical characterization tests. A 150 nm thickness of gold was coated on the DE surfaces by sputter coating under vacuum with different pre-strains, ranging from 0 to 100%. Some of the thin films were transferred to the surface of the DEs. Sputter coating, and direct transferring gold leaf coating methods were studied and the results were analyzed in detail in terms of the strain rates and electrical resistivity changes. Initial studies indicated that the metallic surfaces remain conductive even though the DE films were considerably elongated. The coated DEs can be used as artificial muscle by applying electrical stimulation through the conductive surfaces. This study may provide great benefits to the readers, researchers, as well as companies involved in manufacturing of artificial muscles and actuators using smart materials.
