Dual-Wavelength (UV and Blue) Controlled Photopolymerization Confinement for 3D-Printing: Modeling and Analysis of Measurements

Abstract

The kinetics and modeling of dual-wavelength (UV and blue) controlled photopolymerization confinement (PC) are presented and measured data are analyzed by analytic formulas and numerical data. The UV-light initiated inhibition effect is strongly monomer-dependent due to different C=C bond rate constants and conversion efficacies. Without the UV-light, for a given blue-light intensity, higher initiator concentration (C10) and rate constant (k’) lead to higher conversion, as also predicted by analytic formulas, in which the total conversion rate (RT) is an increasing function of C1 and k’R, which is proportional to k’[gB1C1]0.5. However, the coupling factor B1 plays a different role that higher B1 leads to higher conversion only in the transient regime; whereas higher B1 leads to lower steady-state conversion. For a fixed initiator concentration C10, higher inhibitor concentration (C20) leads to lower conversion due to a stronger inhibition effect. However, same conversion reduction was found for the same H-factor defined by H0 = [b1C10 − b2C20]. Conversion of blue-only are much higher than that of UV-only and UV-blue combined, in which high C20 results a strong reduction of blue-only-conversion, such that the UV-light serves as the turn-off (trigger) mechanism for the purpose of spatial confirmation within the overlap area of UV and blue light. For example, UV-light controlled methacrylate conversion of a glycidyl dimethacrylate resin is formulated with a tertiary amine co-initiator, and butyl nitrite. The system is subject to a continuous exposure of a blue light, but an on-off exposure of a UV-light. Finally, we developed a theoretical new finding for the criterion of a good material/candidate governed by a double ratio of light-intensity and concentration, [I20C20]/[I10C10].

Enhancing UV Photopolymerization by a Red‐light Preirradiation: Kinetics and Modeling Strategies for Reduced Oxygen Inhibition

“…In the second mechanism, as shown by the proposed scheme in Figure 11, 22 in which the photochemical decomposition of butyl nitrite results in the formation of nitric oxide, [N], an efficient inhibitor of radical-mediated polymerizations, and alkoxide radical (X) for extra polymerization initiation, beside the reactive radical (R). Concurrent with the blue-light photoorthogonal, patterned irradiation, the blue-light-produced initiation radical could be reduced/inhibited by [N], such that photopolymerization confinement (PC) is achieved.…”

“…More detailed kinetics and modeling of PC were published elsewhere. 22 Dual-wavelength strategy for customized additive manufacturing requires the following conditions 22 : (a) a wide range of compatible monomers and coinitiators; (b) the photoinhibition of free-radical chain growth can be rapidly switched on and off by cycling the UV light; and (c) the formulated resins can be spatially confined using concurrent blue and UV irradiation. Single-wavelength, conventional, and diffusion-reliant methods with a large inhibition thickness (IT) and high photoinitiation rates offer a continuous and rapid object printing.…”

“…Initiator, coinitiator, and inhibitor, and the dual-wavelength light intensity and dose (or exposure time). 22 The advantages of dual-wavelength concurrent inhibition and initiation photopolymerization include controllable high vertical print speeds, eliminating the need for thin, oxygen-permeable projection windows, single-step fabrication of cured materials, rapid generation of personalized products, and the reflow into the inhibition volume during printing can be optimized for large cross-sectional area parts. Higher light intensity will accelerate the curing speed, but suffers a smaller curing depth and efficacy (at steady state).…”

Concurrent Modelling and Experimental Investigation of Material Properties and Geometries Produced by Projection Microstereolithography

“…A successful PµSLA system, in general, requires an optimized resin formulation. The current available photosensitive resins consist of a single or a mixture of monomers and oligomers, photoinitiator, photoblocker, and enhancing additives [10,[17][18][19]. The concentration of each component influences the process parameter values selected to achieve the desired material properties and geometrical accuracy [20].…”

Moving Towards a Finer Way of Light-Cured Resin-Based Restorative Dental Materials: Recent Advances in Photoinitiating Systems Based on Iodonium Salts

“…The dynamically developing printing industry is a different direction of the application of photopolymerization, which enables printing on plastic or metal materials. Moreover, in recent years, a particular emphasis has been put on the use of photopolymerization processes for 3D-printing technology [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], including stereolithography in the design and formation of three-dimensional models [34].…”