ACS Applied Polymer Materials, January 2020, DOI:10.1021/acsapm.9b01181

3D Printed Microdroplet Curing: Unravelling the Physics of On-Spot Photopolymerization


Vishal Sankar Sivasankar 1, Harnoor Singh Sachar 1, Shayandev Sinha 2, Daniel R. Hines 3, and Siddhartha Das1
1 CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
2 The Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142, USA
3 Laboratory for Physical Sciences, College Park, Maryland 20740, USA

Abstract:

Droplet-based direct-write printing (one form of 3D printing) methods, like inkjet printing, aerosol jet printing (AJP), etc., have changed our ideas about bottom-up additive manufacturing. AJP is capable of 3D printing by depositing microdroplets that lead to certain benefits in 3D printing of microscale structures. Here, we study the in situ photopolymerization-based curing of a microdroplet. The droplet is simultaneously spreading and curing, which leads to the rise of two time scales, the spreading time scale (τs) and the photopolymerization time scale (τp). When τs ≪ τp, the spreading occurs very fast and is independent of polymerization. If the time scales are of the same order (τs ∼ τp), the spreading is significantly affected by the polymerization. For this case, a progressive increase in the viscosity of the drop during the spreading ensures a much slower spreading and also a much weaker extent of spreading (i.e., the spreading ceases at a much smaller spreading radius of the drop). This complex thermofluidics is eventually manifested as distinct differences in the time-dependent velocity, temperature, and curing (or equivalently, monomer concentration) profiles within the drop between the two cases.

This article is available online here and to CALCE Consortium Members for personal review.

[Home Page] [Articles Page]
Copyright © 2020 by CALCE and the University of Maryland, All Rights Reserved