First observation of the effect of the layer printing sequence on the molecular structure of three-dimensionally printed polymer, as shown by in-plane capacitance measurement

The layer printing sequence in three-dimensional (3D) printing affects the molecular structure of the printed layers, as shown for bottom-up stereolithography printing using an ultraviolet-curable acrylate ester resin. The first printed layer has less molecular alignment than the last printed layer, due to the longer ultraviolet exposure and consequent more curing in the former. Increasing the layer thickness from 12.4 to 26.3 μm decreases this effect, due to the greater molecular alignment for a smaller layer thickness. These results are obtained by measuring the in-plane capacitance for the two opposite surfaces of the printed material. The technique is unprecedented in 3D printing.