Fabrication of multi-material dielectric elastomer actuators with the additive manufacturing process of material extrusion

Philipp Beier

Research output: ThesisMaster's Thesis

Abstract

Dielectric elastic actuators (DEA) are versatile devices with various applications, such as in the field of soft robotics or sensor measurement technology. Additive manufacturing (AM) enables the production of various materials with complex geometries in a layer-by-layer process, and material extrusion (MEX) is a highly promising subcategory of it. In this process, filaments are utilised and passed through an extruder to create the component in a sequential manner, layer by layer. There are various methodologies for producing parts made of multiple materials. This study employed a multi-extruder approach to address the issues associated with processing soft materials that are difficult to handle. Materials that contain additives like graphite can potentially contaminate the nozzle, resulting in increased difficulty when attempting to clean it. Therefore, a novel tool was developed to manage four extruders on a single axis. Moreover, they were mounted on two separate movable carriages, each capable of accommodating two extruders. Dual extruders have become well-established in the industry and are widely used in the commercial sector. It is an efficient and simple method to simultaneously process two materials in a single print. In order to verify the precision and consistency of the custom printer, various measurements were performed, including capacitance and the overall thickness of the produced parts. The machine was required to reliably produce layers with a height of 70 ¿m. The deviation reached a maximum of 8%, which is a commendable outcome considering the limitations of the hardware. Another section of the thesis focused on the analysis of various types of polyurethanes (TPU) for the purpose of DEAs. The study examined the impact of varying shore hardness levels and printing orientations on material selection. The investigation revealed that using an infill orientation of either 0° or 90° yielded similar values for both the Young's modulus and flexural modulus. This can be attributed to the seamless melding of the strings, resulting in minimal differences between orientations. Regarding the shore hardness of the materials, they exhibited comparable bending stiffness across a range of 83A to 20D. A significant increase of over 20% in the Young's modulus was observed only when the hardness reached 40D. The moduli of the TPUs used as electric-conductive materials were even higher. This phenomenon may be attributed to the graphite particles, which embed themselves within the gaps in the chains, thereby enhancing the material's rigidity. The DEAs that were produced underwent displacement measurements to determine their functionality. As anticipated following the mechanical test, all actuators exhibited comparable displacements. The findings suggest that the capacitance of the actuator is the main factor influencing the result. When the capacitance is decreased, the displacement is proportionally reduced. Based on the actuators that were tested, a prototype application was designed and manufactured. Three actuators were linked in parallel and served as gripping arms.
Translated title of the contributionHerstellung von Multimaterial-Aktuatoren aus dielektrischen Elastomere mit dem additiven Fertigungsverfahren der Materialextrusion
Original languageEnglish
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Holzer, Clemens, Supervisor (internal)
Award date28 Jun 2024
Publication statusPublished - 2024

Bibliographical note

no embargo

Keywords

  • Additive manufacturing (AM)
  • Dielecttric elastomer actuators (DEA)
  • Multi-material extruder

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