Printing stable liquid tracks on a surface with finite receding contact angle.

Wen-Kai Hsiao,Graham D Martin,Ian M Hutchings

doi:10.1021/la502490p

Wen-Kai Hsiao, Graham D Martin + Show 1 more

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https://doi.org/10.1021/la502490p

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Abstract

We have used high-speed imaging to study the formation of liquid tracks on a surface with nonzero receding contact angle, by the sequential deposition of liquid drops. For small drop spacing we found good agreement with the track morphology predicted by an existing line stability model. In addition, we confirmed definitively the preferential drop-to-bead fluid flow and the predicted drop spreading variation in the scalloped line and paired bead formation regimes. However, we found that without accounting for drop impact inertia, the model underestimated the maximum drop spreading radii and, hence, the instantaneous track width. In addition, the printed track became stable at larger drop spacing, in contrast to the expected behavior. We believe that the destabilizing effect of a receding contact line may be minimized when track radii, as predicted by volume conservation and drop-bead coalescence dynamics, converge as the drop spacing increases. An increase in viscous dissipation and a reduction of the capillary-driven flow may be the additional stabilization mechanisms. The latter may also be responsible for achieving a stable and symmetrical track when printing with a shorter interval (higher print frequency) at a given drop spacing.

Highlights

With the current advances in 3-D printing and printed electronics applications, functional ink-jet printing has attracted significant research and development efforts
By printing a mixture of water and ethylene glycol to form short tracks on a surface with a finite receding contact angle, we aimed to verify the line stability mechanisms proposed by Soltman and Subramanian and to explore whether it is possible to produce a printed track with mobile contact line that is stable over the time scale of typical ink-jet printing processes
We have carried out a series of high-speed imaging experiments to study the dynamics of liquid track formation on a surface with a nonzero receding contact angle, as typically observed in practical applications

Summary

Introduction

With the current advances in 3-D printing and printed electronics applications, functional ink-jet printing has attracted significant research and development efforts. In contrast to graphical applications in which the printed images are formed by discrete ink deposits derived from single or in some cases multiple drops, printed functional patterns are often continuous features, such as lines or tracks, formed by the merging of individually deposited liquid drops on the surface The functionality of these printed patterns, be it the conductivity of a printed circuit track or the structural integrity of a 3-D printed object, can depend strongly on their geometrical quality. Incorporating the finding of Duineveld, they further mapped the region of stability defined by the equilibrium contact angle, drop spacing, and print velocity

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