There is demand for scaling up 3D printing throughput, especially for the multi-photon 3D printing process that provides sub-micrometer structuring capabilities required in diverse fields. In this work, high-speed projection multi-photon printing is combined with spatiotemporal focusing for fabrication of 3D structures in a rapid, layer-by-layer, and continuous manner. Spatiotemporal focusing confines printing to thin layers, thereby achieving print thicknesses on the micron and sub-micron scale. Through projection of dynamically varying patterns with no pause between patterns, a continuous fabrication process is established. A numerical model for computing spatiotemporal focusing and imaging is also presented which is verified by optical imaging and printing results. Complex 3D structures with smooth features are fabricated, with millimeter scale printing realized at a rate above 10−3 mm3 s−1. This method is further scalable, indicating its potential to make fabrications of 3D structures with micro/nanoscale features in a practical time scale a reality.

Printing of high‐resolution three‐dimensional nanostructures utilizing two‐photon polymerization has gained significant attention recently. In particular, isopropyl thioxanthone (ITX) has been implemented as a photoinitiator due to its capability of initiating and depleting polymerization on demand, but new photoinitiating materials are still needed in order to reduce the power requirements for the high‐throughput creation of 3D structures. To address this point, a suite of new thioxanthone‐based photoinitiators were synthesized and characterized. Then two‐photon polymerization was performed using the most promising photoinitiating molecule. Importantly, one of the initiators, 2,7‐bis[(4‐(dimethylamino)phenyl ethynyl)‐9H‐thioxanthen‐9‐one] (BDAPT), showed a fivefold improvement in the writing threshold over the commonly used ITX molecule. To elucidate the fundamental mechanism, the excitation and inhibition behavior of the BDAPT molecule were evaluated using density functional theory (DFT) calculations, low‐temperature phosphorescence spectroscopy, ultra‐fast transient absorption spectroscopy, and the two‐photon Z‐scan spectroscopic technique. The improved polymerization threshold of this new photoinitiator presents a clear pathway for the modification of photoinitiators in 3D nanoprinting. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1462–1475

Nanolithographic printing by direct laser writing (DLW) photopolymerization has attracted increased attention in recent years, as the speed of this printing has increased, while the feature sizes that have been realized have decreased well into the nanoscale regime. Specifically, isopropyl thioxanthone (ITX) has been utilized as one of the common photoinitiators in DLW polymerization processes because of its high-efficiency photoinitiating abilities and its ability to have its initiation properties inhibited through the application of a second wavelength of light. However, improved photoinitiating materials that are built from this successful archetype are required, by both academic and industrial circles, if advanced highthroughput nanomanufacturing techniques are to be implemented. Here, nextgeneration thioxanthone-based photoinitiators with tailored optical and charge transfer properties were computationally designed and subsequently synthesized. Particularly, branches with specifically modulated electron donor and electron acceptor qualities, relative to the ITX core, were coupled to the initial thioxanthone substrate. After having their molecular and optical properties characterized in full, it was evident that these initiators possessed a clear advancement in terms of photopolymerization initiation relative to ITX. As such, a champion photoinitiator chemistry was brought forward to demonstrate enhanced two-photon polymerization DLW such that superresolution properties were exhibited. In this way, we introduce a clear means by which to systematically design future photoinitiators for enhanced two-photon polymerization DLW nanoprinting processes.

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In the present study, 94 dental patients received either monitoring (i.e., paying attention) or blunting (i.e., distraction) coping instructions during treatment. Half of the patients were given the possibility of choice, whereas the other half were offered one of both strategies without choice. A majority of the patients (n=61) indicated that the intervention had resulted in a decrease of their anxiety. Some indications were found for the monitoring strategy to be more effective than the blunting strategy. More specifically, monitoring strategy subjects reported that they had experienced less distress during treatment than blunting strategy subjects. In agreement with this finding, self-efficacy ratings of monitoring strategy subjects were higher than those of blunting strategy subjects. Possibility of choice and coping preference had no substantial influence on effectiveness of the interventions.