Viscoplastic Lines: Printing a Single Filament of Yield Stress Material on a Surface

TL;DR

This paper investigates the spreading behavior of a single yield stress filament on a surface, deriving a scaling law and validating it through experiments relevant to advanced printing technologies.

Contribution

It introduces a new scaling law for filament spreading and compares theoretical predictions with experimental results in the context of viscoplastic printing.

Findings

The scaling law accurately predicts the final filament width.

Experimental measurements align well with the theoretical model.

Discrepancies are discussed with potential causes identified.

Abstract

This study presents the spreading of a single filament of a yield stress (viscoplastic) fluid extruded onto a pre-wetted solid surface. The filaments spread laterally under surface tension forces until they reach a final equilibrium shape when the yield stress dominates. We use a simple experimental setup to print the filaments on a moving surface and measure their final width using optical coherence tomography. Additionally, we present a scaling law for the final width and determine the corresponding pre-factor using asymptotic analysis. We then analyse the level of agreement between the theory and experiments and discuss the possible origins of discrepancies. The process studied here has applications in extrusion-based thermoplastic and bio-3D printing.