Systematic approach to development of pressure sensors using dielectric electro-active polymer membranes

Abstract

Dielectric electro-active polymers (DEAPs) have become attractive materials for various actuation and sensing applications due to their high energy and power density, high efficiency, light weight, and fast response speed. However, commercial development has been hindered due to a variety of constraints such as reliability, non-linear behavior, cost of driving electronics, and form factor requirements. This paper presents the systematic development from laboratory concept to commercial readiness of a novel pressure sensing system using a DEAP membrane. The pressure sensing system was designed for in-line pressure measurements for low pressure applications such as health systems monitoring. A first generation sensor was designed, built and tested with a focus on the qualitative capabilities of EAP membranes as sensors. Experimental measurements were conducted that demonstrated the capability of the sensor to output a voltage signal proportional to a changing pressure. Several undesirable characteristics were observed during these initial tests such as strong hysteresis, non-linearity, very limited pressure range, and low fatigue life. A second generation prototype was then designed to remove or compensate for these undesirable characteristics. This prototype was then built and tested. The new design showed an almost complete removal of hysteretic non-linear effects and was capable of operating at 10 × the pressure range of the initial generation. This new design is the framework for a novel DEAP based pressure sensor ready for commercial applications.

A Review of Dielectric Elastomer Generator Systems

“…[24] Finally, in DE sensors, capacitance variation measurements are exploited to sense a stretch or an applied force. [25] Specifically, the operating principle of a DEG can be described in terms of a cyclic sequence of electromechanical transformations. To give an example, we make reference to a positioncontrolled planar DEG unit subject to uniform stretches on the electrodes plane, driven according to a cycle ( Figure 1a) with the following phases:…”

Comparison of Piezoresistive Monofilament Polymer Sensors

“…EAPs based on elastomers coated with conductive layers have been investigated for flexible force actuator applications. In a sensor configuration, highly flexible capacitive sensors can be created [ 14 ]. A problem though is that capacitive sensing is based on the assumption that the gap between electrodes will change, while the electrical boundary conditions of the electrodes will remain constant [ 15 ].…”

“…For example, if a parallel capacitive sensor is designed using a flexible electrode, the electrode area increases as the sensor is compressed. Then the sensor signal changes due to the decrease in gap distance between the electrodes, as well as due to the change in resistance of the electrode geometry changing [ 14 , 16 ]. With dielectric elastomers one primary research goal is the development of compliant electrodes, where a change in mechanical dimension does not lead to a large change in resistivity of the material [ 17 ].…”

Modeling and control of innovative smart materials and actuators: A tutorial

“…From the electrical point of view DEAP are variable capacitors, whose capacitance is a function of the membrane deformation. DEAP can then be used as deformation or pressure capacitive sensors [6]. Thus, the capacitance measurement can be used to perform sensing while actuating in the so-called self-sensing operation [7] (e.g., sensorless position control).…”