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).
Inspired from the natural invertebrates like worms and starfish, we propose a novel elastomeric smart structure. The smart structure can function as a soft robot. The soft robot is made from a flexible elastomer as the body and driven by dielectric elastomer as the muscle. Finite element simulations based on nonlinear field theory are conducted to investigate the working condition of the structure, and guide the design of the smart structure. The effects of the prestretch, structural stiffness and voltage on the performance of the smart structure are investigated. This work can guide the design of soft robot.
The natural limbs of animals and insects integrate muscles, skins and neurons, providing both the actuating and sensing functions simultaneously. Inspired by the natural structure, we present a novel structure with integrated function of actuating and sensing with dielectric elastomer (DE) laminates. The structure can deform when subjected to high voltage loading and generate corresponding output signal in return. We investigate the basic physical phenomenon of dielectric elastomer experimentally. It is noted that when applying high voltage, the actuating dielectric elastomer membrane deforms and the sensing dielectric elastomer membrane changes the capacitance in return. Based on the concept, finite element method (FEM) simulation has been conducted to further investigate the electromechanical behavior of the structure.
Three dimensional responsive structures have high value for the application of responsive hydrogels in various fields such as micro fluid control, tissue engineering and micro robot. Whereas various hydrogels with stimuli-responsive behaviors have been developed, designing and fabricating of the three dimensional responsive structures remain challenging. We develop a temperature responsive double network hydrogel with novel fabrication methods to assemble the complex three dimensional responsive structures. The shape changing behavior of the structures can be significantly increased by building blocks with various responsiveness. Mechanical instability is built into the structure with the proper design and enhance the performance of the structure. Finite element simulation are conducted to guide the design and investigate the responsive behavior of the hydrogel structures