Additive manufacturing of self-healing polymers for soft robotics applications

Abstract

With nature as their main source of inspiration, soft robotics is a fast growing field of research. Their inherent softness and flexibility allows for safe interaction with their environment, but makes them also fragile. Whereas traditional (soft) robots are unable to repair themselves after damage, new research in the field of self-healing polymers for soft robotics shows promising results. Self-healing robotic actuators have been successfully developed using elastomeric polymer
networks based on thermoreversible Diels-Alder bonds. Up until now, these self-healing actuators are manufactured using a process called shaping-through-folding-and-self-healing, which is labour intensive and limits the design options. In this thesis, a proof of concept for additive manufacturing of self-healing elastomeric polymers is presented. In this work, Fused Filament Fabrication, also known as 3D-printing, is considered. For the development of this process, a
first step is to obtain gilament for the 3D-printer. This is accomplished by an extrusion process that is optimized specically for the Diels-Alder networks. The optimization exists of finding several parameters and overcoming the observed failure phenomena. The second step is the 3D-printing itself, which strongly depends on the quality of the obtained filament. This technique was adapted and optimized to make 3D-printing of flexible Diels-Alder elastomers possible. The
material was successfully printed and it was proven through experimental verification that the mechanical and chemical properties of the material remain equal before and after the filament extrusion and printing process. However, some limitations remain in the printing process, such as printing overhang, due to the chemical nature of the material. The self-healing properties show also their benefit on the quality of the print: due to the healing, the layer marks that are typical for 3D-printed parts disappear and the parts are airtight. This allowed to print several proofs of concept for soft robotic actuators. 3D-printing of the self-healing actuators allows for a wider range of designs, faster prototyping, and the use of multiple self-healing materials with different mechanical properties within the same design. In addition, the Diels-Alder elastomer networks have the advantage of being completely recyclable, a property used and illustrated throughout this thesis.

Date of Award	7 Jul 2018
Original language	English
Supervisor	Bram Vanderborght (Promotor) & Guy Van Assche (Co-promotor)