Alleviating Distortion and Improving the Young’s Modulus in Two-Photon Polymerization Fabrications

Abstract

Two-photon polymerization enables the extremely high resolution three-dimensional printing of micro-structures. To know the mechanical properties, and better still, to be able to adjust them is of paramount importance to ensuring the proper structural integrity of the printed products. In this work, the Young’s modulus is measured on two-photon polymerized micro-cantilever bars. Optimizing the scanning trajectory of the laser focus points is important in alleviating distortion of the printed bars. By increasing the laser power and decreasing the inter-voxel distances we can double the Young’s modulus. Post-curing with ultraviolet light can approximately quadruple the Young’s modulus. However, the resulting modulus is still only about 0.3% of that of the bulk polymerized material.

Effect of micron-scale manufacturing flaws on the tensile response of centimeter sized two-photon polymerization microlattices

“…2(b)]. This increase agrees with results from other mechanical studies performed on unit-block [20][21][22] and single voxel-line objects. [23,24] The increase of the modulus was attributed to higher degrees of conversion and larger voxel cross-sectional dimensions resulting from increased light intensity.…”

Assessing the Viscoelasticity of Photopolymer Nanowires Using a Three-Parameter Solid Model for Bending Recovery Motion

“…Interestingly, the differences diminished when operating similar micro-coils on air or in a vacuum [11]. The same buffer solution effect was observed for micro-cantilevers [12,13]. By contrast, elastic moduli near to bulk values were reported for micro-cantilevers [14] and nanowires [15] operated at dry conditions.…”

“…The elastic moduli size-scaling reported for micro-and nano-sized objects was ambiguous. Depending on the conditions, both increasing [11,16] and decreasing [10,12,13,17] elastic moduli were observed towards smaller object dimensions. As discussed recently by Lad-ner et al [16], the competing impacts of enhanced polymer chain alignment and the lower degree of conversion in smaller features may explain the contradictory results.…”

Bending dynamics of viscoelastic photopolymer nanowires

“…26,27 The question arises whether or not the viscous character of the uncured resin and the penetrated solvent affects the mechanical properties of the nanostructures prepared by TPP-DLW. Optical tweezers, 18,21,28 nanoindentation equipment, 24,25 atomic force microscopes, 17,19,29 and, more recently, micro-electro-mechanical systems (MEMS)-based tensile testers 20 and nanorobotic systems 22 were utilized to follow the photopolymer response to the applied mechanical stress. With a few exceptions, all the results used for elastic modulus evaluation were obtained at quasisteady conditions.…”