Disorders associated with the lower extremity venous system are common and significantly affect the quality of life of a large number of individuals. These disorders include orthostatic hypotension, oedema, deep vein thrombosis and a number of other conditions related to insufficient venous blood return. The common recommended treatment for these disorders is the use of hosiery compression stockings. In this research, an active compression bandage (ACB) based on the technology of dielectric elastomeric actuators (DEA) was designed, prototyped and tested. A customized calf prototype (CP) was developed to measure the pressure applied by the ACB. Experimental results performed with the CP showed that the pressure applied by the ACB could be electrically controlled to be either below or above the pressure exerted by commercially available compression stockings. An analytical model was used to provide the design criteria. A finite element model (FEM) was also developed to simulate the electromechanical behaviour of the DEA. Comparison of the experimental results with the FEM and analytical models showed that the modelling could accurately predict the behaviour of the ACB. The FEM was subsequently used to study how to improve the ACB performance by varying geometrical parameters such as the ACB thickness.

Novel devices based on the use of dielectric elastomer actuators (DEA) have been proposed for a large variety of different applications. In many of these applications, DEAs are envisioned to be in direct or close proximity to the human body. Since DEAs usually require high voltage for their actuation, the safety of individuals operating or using these devices should be ensured. In this paper, safety standards based on safe limits for electrical discharge are investigated. Flat and cylindrical DEA configurations, which are generally considered as the building blocks for the design of DEA-based systems, are investigated in detail. Relevant elements and factors that affect the electrical discharge of DEA devices are analyzed and guidelines to design DEA-based devices that are not of harm for humans are provided. The performed analyses are experimentally validated using flat DEA samples. The safety requirements that should be considered when wrapping DEAs around the body (specifically the legs) are also briefly investigated to provide a practical example of interest for the biomedical community.

A novel soft grasping gripper which is based on dielectric elastomer actuators (DEAs) is presented in this paper. The gripper presents a self-contained and inherently soft approach for grasping objects. A single actuator membrane based on an acrylic elastomer inflates upon application of high electrical voltages. The actuation deformation of the membrane results in a frictional grasp of an underlying object from multiple angles simultaneously. The gripper comprises of a pressurized chamber sealed by the cylindrical DEA and relies on the friction force between the DEA membrane and the object. Mathematical analyses are carried out to simulate the actuation deformation of the DEA membrane and to estimate the grasping force with 3 cylindrical objects of different sizes. Experimental results validate the analytical analyses and show up to around 20% of membrane actuation deformation and 2N of grasping forces.

BackgroundOne of the recommended treatments for disorders associated with the lower extremity venous insufficiency is the application of external mechanical compression. Compression stockings and elastic bandages are widely used for the purpose of compression therapy and are usually designed to exert a specified value or range of compression on the leg. However, the leg deforms under external compression, which can lead to undesirable variations in the amount of compression applied by the compression bandages. In this paper, the use of an active compression bandage (ACB), whose compression can be regulated through an electrical signal, is investigated. The ACB is based on the use of dielectric elastomer actuators. This paper specifically investigates, via both analytical and non-linear numerical simulations, the potential pressure the ACB can apply when the compliancy of the human leg is taken into account. The work underpins the need to account for the compressibility of the leg when designing compression garments for lower extremity venous insufficiency.MethodsA mathematical model is used to simulate the volumetric change of a calf when compressed. Suitable parameters for this calf model are selected from the literature where the calf, from ankle to knee, is divided into six different regions. An analytical electromechanical model of the ACB, which considers its compliancy as a function of its pre-stretch and electricity applied, is used to predict the ACB’s behavior. Based on these calf and ACB analytical models, a simulation is performed to investigate the interaction between the ACB and the human calf with and without an electrical stimulus applied to the ACB. This simulation is validated by non-linear analysis performed using a software based on the finite element method (FEM). In all simulations, the ACB’s elastomer is stretched to a value in the range between 140 and 220 % of its initial length.ResultsUsing data from the literature, the human calf model, which is examined in this work, has different compliancy in its different regions. For example, when a 28.5 mmHg (3.8 kPa) of external compression is applied to the entire calf, the ankle shows a 3.7 % of volume change whereas the knee region undergoes a 2.7 % of volume change. The paper presents the actual pressure in the different regions of the calf for different values of the ACB’s stretch ratio when it is either electrically activated or not activated, and when compliancy of the leg is either considered or not considered. For example, results of the performed simulation show that about 10 % variation in compression in the ankle region is expected when the ACB initially applies 6 kPa and the compressibility of the calf is first considered and then not considered. Such a variation reduces to 5 % when the initial pressure applied by the ACB reduced by half.ConclusionsComparison with non-linear FEM simulations show that the analytical models used in this work can closely estimate interaction between an active compression bandage and a human calf. In addi...

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