Guoyong Mao

Dielectric elastomer peristaltic pump module with finite deformation

Inspired by various peristaltic structures existing in nature, several bionic peristaltic actuators have been developed. In this study, we propose a novel dielectric elastomer peristaltic pump consisting of short tubular modules, with the saline solution as the electrodes. We investigate the performance of this soft pump module under hydraulic pressure and voltage via experiments and an analytical model based on nonlinear field theory. It is observed that the individual pump module undergoes finite deformation and may experience electromechanical instability during operations. The driving pressure and displaced volume of the peristaltic pump module can be modulated by applied voltage. The efficiency of the pump module is enhanced by alternating current voltage, which can suppress the electromechanical pull-in instability. An analytical model is developed within the framework of the nonlinear field theory, and its predictive capacity is checked by experimental observations. The effects of the prestretch, aspect ratio, and voltage on the performance of the pump modules are characterized by the analytical model. This work can guide the designs of soft active peristaltic pumps in the field of artificial organs and industrial conveying systems.

Viscoelastic effect on the wrinkling of an inflated dielectric-elastomer balloon

Viscoelasticity plays an important role in the instability and performance of soft transducers. Wrinkling, an instability phenomenon commonly observed on soft materials, has been studied extensively. In this paper, we theoretically investigate the viscoelastic effect on the wrinkle formation of a dielectric-elastomer (DE) balloon subjected to combined electromechanical loads. Results show that the critical voltage for the wrinkle formation of a DE balloon gradually decreases as the material undergoes viscoelastic relaxation and finally reaches a stable value. The wrinkles in the lateral direction always have critical voltages equal to or lower than those in the longitudinal direction. What is more, the nucleation sites of wrinkles always move from the apex to the rim of DE balloon with the viscoelastic relaxation of DE. It takes less time for the DE balloon with higher pressure to reach the stable state. Higher pressure also leads to the stable wrinkle nucleation site moving closer to the fixed edge of the DE balloon. An experiment is conducted to illustrate the effect of viscoelasticity on the wrinkle propagation of a DE balloon, and the results agree well with the model predictions. This study provides a guide in the wrinkling control of a DE balloon and may help the future design of DE transducers. [DOI: 10.1115/1.4039672]

Voltage-controlled radial wrinkles of a trumpet-like dielectric elastomer structure

Wrinkle is usually considered as one failure mode of membrane structure. However, it can also be harnessed in developing smart devices such as dry adhesion tape, diffraction grating, smart window, etc. In this paper, we present a method to generate voltage-controlled radial wrinkles, which are fast response and reversible, in a stretched circular dielectric elastomer (DE) membrane with boundary fixed. In the experiment, we bond a circular plate on the center of the circular membrane and then pull the DE membrane perpendicular to itself via the plate. The stretched DE membrane is a trumpet-like structure. When the stretched DE membrane is subjected to a certain voltage, wrinkles nucleate from the center of the DE membrane and propagate to the boundary as the voltage increases. We adopt a theoretical framework to analyze the nucleation of the wrinkles. A simple wavelength expression is achieved, which is only related to the geometry and the stretch of the DE membrane. Results show that the theory agrees well with the experiment. This work may help the future design of DE actuators in avoiding mechanical instability and provide a new method to generate controllable radial DE wrinkles.Wrinkle is usually considered as one failure mode of membrane structure. However, it can also be harnessed in developing smart devices such as dry adhesion tape, diffraction grating, smart window, etc. In this paper, we present a method to generate voltage-controlled radial wrinkles, which are fast response and reversible, in a stretched circular dielectric elastomer (DE) membrane with boundary fixed. In the experiment, we bond a circular plate on the center of the circular membrane and then pull the DE membrane perpendicular to itself via the plate. The stretched DE membrane is a trumpet-like structure. When the stretched DE membrane is subjected to a certain voltage, wrinkles nucleate from the center of the DE membrane and propagate to the boundary as the voltage increases. We adopt a theoretical framework to analyze the nucleation of the wrinkles. A simple wavelength expression is achieved, which is only related to the geometry and the stretch of the DE membrane. Results show that the theory agrees wel...

Electromechanical behavior of a novel dielectric elastomer sensor for compressive force detection(Conference Presentation)

Dielectric elastomers (DEs) have been extensively studied as DE actuators, DE generators, and DE sensors. Compared with DE actuators and generators, DE sensing application has the advantage that it is no need for high voltage. However, to realize the high sensitivity of the DE sensor, a well-designed structure is essential. A typical DE sensor consists of DE membrane covered by compliant electrodes on both sides. Expanding in the area and shrinking in the thickness of DE membrane subjected to external force will lead to the increasement of the capacitance. We propose a novel DE sensor to detect compressive force. The DE sensor consists of three layers. The two layers of outside can penetrate each other to deform the middle layer and achieve high sensitivity for compressive force measurement. This sensor consists of a series of sensor elements made of DE membrane with out-of-plane deformation. Each sensor element experiences highly inhomogeneous large deformation to obtain high sensitivity. We conduct the experiment to optimize the performance of the sensor element, and also the corresponding theoretical analysis is developed. The effects of the prestretches and the aspect ratios of the sensor element on the sensitivity are achieved. The soft sensor composed of a series of such sensor elements may comply with complicated surfaces and can be used to detect both the total value and the distribution of the compressive force exerted on the surface. Furthermore, the reliability of the sensor element is studied by additional experimental investigation. The experiment shows that the sensor element operates steadily after 2000 cyclic loadings. This study provides guidance for the design and performance analysis of soft sensors. This work has been published in the Journal of Applied Mechanics, 82(10), No. 101004 (2015).