Coaxial extrusion processes: Experimental effort toward 4d printed dielectric soft actuators

Abstract

Emerging within the field of advanced additive manufacturing, 4D printing of thermal-responsive systems introduces dynamic transformations to printed products when subjected to thermal stimuli. However, these systems exhibit comparatively sluggish actuation speeds due to the gradual nature of thermal variations. This study addresses this limitation by introducing an approach centred on a sequential stimulus mechanism. By integrating an electro-active mechanism fueled by thermoelectric energy harnessed from the Seebeck effect, the proposed system holds the potential to substantially enhance actuation speed within thermal-responsive domains to 2 sec with actuators of 1mm cross-section. To validate this concept, a custom ink-jet printing setup with distinct nozzles was constructed, and initial ink rheology testing and simulations were conducted. The minimum pressure needed to achieve the shear-thinning behaviour required for printing, as well as the time frame in which the ink is printable, were also defined. The research also focuses on presenting the working principles and establishing configurations and precautions needed when direct ink printing shear-thinning inks such as the printing bed material. It also proposes preliminary work for the automatization of the printing process, especially concerning pressure control.