Physicalization helps the user understand complex data intuitively. Especially when confronted with complex, multidimensional datasets as in the smart home environment, classic graphical user interfaces struggle to visualize data in a way compatible with the paradigm of Calm Technology and new means of displaying data need to be explored, to decrease the cognitive burden on the user. Shape changing interfaces (SCI) using smart materials can change their appearance under electrical stimuli and provide the means to physicalize the data found in the smart home from sensors, appliances or others. Within the scope of this work, a smart display using dielectric elastomer unimorph actuators (UDEA) is developed, which can be used to explore how dielectric elastomers (DE) can be used for an SCI. A dynamic model of previous work has been adapted to the updated geometry. Reproducible production of the actuators is one focus of the current work. A novel sheet-to-sheet process for manufacturing multilayer DE-laminates is presented. Manual processing of the laminates to actuators is described and effects of human error on actuator performance in this process is assessed and found to be low to ensure reproducible fabrication. Finally the system design is presented and discussed. The developed display allows controlling 15 independent shape changing devices and will allow to gain more knowledge about physicalization of data using DE actuators.
This contribution proposes a vaporization and recovery system for the contactless printing of solvent-based electrodes. The developed system prevents swelling effects, which frequently occur when solvent-based electrode material interacts with the elastomer film. In addition, this novel system features recovery of the vaporized solvent by extraction. For this purpose, the heat transport and vaporization process is theoretically analyzed to design and realize the system. Finally, various tests are conducted with the integrated jetting system to evaluate the functions and performance of the developed system.
In general, materials for dielectric elastomer (DE) transducers, i.e. elastomer and electrode materials, are characterized by their electromechanical behavior. Whereas previous works frequently focus on the mechanical characterization of the elastomer material, this contribution deals with the mechanical characterization of two electrode materials, ELASTOSIL ® LR 3162 (EL 3162) and POWERSIL® 466 (PS 466), as well as the elastomer material ELASTOSIL ® 2030 (EL 2030). The mechanical behavior of the elastomer and electrode materials is determined by elastic and viscous properties such as creep and relaxation. In addition, the electrode materials, exhibit a significant rate-independent hysteresis, which is well-known for filled elastomer materials. A material model based on rheological, mechanical elements is introduced to describe these material properties, and experimental investigations are done to perform a parameter identification for the material model. Experimental investigations show a higher Young’s modulus, higher viscous losses, and an additional rate-independent hysteresis for the electrode materials compared to the elastomer material. In conclusion, the impact of the material properties of the electrode materials on the DE-transducer performance by thinning the elastomer film is discussed.
In this contribution, 3D printing of elastomer layers is investigated. 3D printing gains emerging interest due to its versatility in geometry as well as the ability of producing thin layers and therefore is a promising fabrication method for dielectric elastomer transducers (DETs). Direct Ink Writing (DIW) is a specific type of 3D printing based on the extrusion of fluidic elastomer with middle viscosity, which is the used printing technology in this work. The printing requirements for DETs are defined and by varying the process parameters, printing tests are conducted. Finally, the layers are analyzed and the results are discussed. The main results are printing of a single layer elastomer with 40 µm thickness and three elastomer layers printed on top of each other.
Transducers based on dielectric elastomers (DEs) consist of a polymer as dielectric between two compliant electrodes and can convert electrical into mechanical energy and vice versa. The geometry significantly determines the performance of DEs, which is mainly reflected by the static and dynamic behavior of pressure and strain. The goal of multilayered dielectric elastomer stack-transducers (DETs) is to maximize the force while maintaining a reasonable deflection. To scale the voltage down to 1 kV the thickness of the elastomeric film must be reduced. For this purpose, a roll-to-sheet lamination process has been adopted by modifying an existing process in order to use elastomeric films with a thickness of 20 µ m, applied with electric field strength up to 50 V/ µ m. In a first step, 10 films are laminated in a semi-automated process resulting in submodules. Fully functional submodules are stacked to form a multilayered stack-transducer up to hundreds of thin films. The production process can be divided into 5 partial processes which are described in detail. The goal of each manufacturing step as well as challenges are presented. With this outline, the outcome of the mentioned manufacturing approach of thin film-based multilayered DE stack-transducers is investigated. The roll-to-sheet lamination approach to produce DETs via submodules provides a good basis for further research in this field.
This paper investigates a droplet based dispensing method for the application of compliant electrode layers for Dielectric Elastomer (DE) transducers and presents the characterization of the deposited electrodes. It is a non-contact, robust and in terms of the material requirements versatile method. As electrodes, three different carbon black based materials are prepared for the deposition by adjusting their fluid properties. The working principle of the deposition method is introduced and the deposition parameters are determined. Subsequently, the electrode materials are deposited on the very thin dielectric elastomer film. The electrical and mechanical properties of the deposited electrodes are experimentally characterized. A surface resistance of 4.1 kΩ at 4.5 µm thickness is measured and no significant stiffening is observed up to 20 % elongation. The investigated deposition technique is able to deposit the particle filled electrode materials with a relatively wide viscosity range without contact and a homogeneous thickness of under 5 µm within the deposited area.
Dielectric elastomer (DE) transducers consist of a dielectric elastomer layer coated with flexible electrodes on both surfaces. Apart from the dielectric film, the properties of the electrodes affect the electromechanical behavior of the DEtransducers as well. Electrodes must be able to sustain conductivity at large deformations, must exhibit a low stiffness and provide sufficient adhesion to the DE-layer. Different processing technologies exist for application of electrodes suitable for DE-transducer. Among them, the inkjet printing technique gained attention in recent years as a very precise and purely non-contact deposition method to fabricate thin electrode layers. In contrast to other methods, e. g. using a shadow mask in case of spraying, the inkjet technique is very versatile and allows a fast adjustment of the processed electrode geometry. In order to describe the requirements of the inkjet printing process and ink adaptation itself, we present a theoretical description of those processes accompanied with the definition of parameters, which need to be considered during experimental processing. Furthermore, we present first results of our adaptation of an ink formulation and an inkjet printing procedure. For this purpose a commercial electrode paste, Elastosil LR 3162, made of carbon black-silicone composite, was adapted to the inkjet printing process. In first experimental studies, the adapted ink was inkjet printed onto dielectric elastomer layers by varying the inkjet printing parameters. Different measurements were performed in order to characterize separate dots as well as continuous lines and areas of the inkjet printed electrodes. The electrode thicknesses and its shapes were recorded by surface-profile measurements. The electrical properties of the printed electrodes as well as their mechanical influence on the elastic properties of the elastomer layers were measured under continuous and cyclic mechanical stretching.
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