Triplet Upconversion under Ambient Conditions Enables Digital Light Processing 3D Printing

Abstract

The rapid photochemical conversion of materials from liquid to solid (i.e., curing) has enabled the fabrication of modern plastics used in microelectronics, dentistry, and medicine. However, industrialized photocurables remain restricted to unimolecular bond homolysis reactions (Type I photoinitiations) that are driven by high-energy UV light. This narrow mechanistic scope both challenges the production of high-resolution objects and restricts the materials that can be produced using emergent manufacturing technologies (e.g., 3D printing). Herein we develop a photosystem based on triplet−triplet annihilation upconversion (TTA-UC) that efficiently drives a Type I photocuring process using green light at low power density (<10 mW/cm 2 ) and in the presence of ambient oxygen. This system also exhibits a superlinear dependence of its cure depth on the light exposure intensity, which enhances spatial resolution. This enables for the first-time integration of TTA-UC in an inexpensive, rapid, and high-resolution manufacturing process, digital light processing (DLP) 3D printing. Moreover, relative to traditional Type I and Type II (photoredox) strategies, the present TTA-UC photoinitiation method results in improved cure depth confinement and resin shelf stability. This report provides a user-friendly avenue to utilize TTA-UC in ambient photochemical processes and paves the way toward fabrication of next-generation plastics with improved geometric precision and functionality.

Silicon-photonics-enabled chip-based 3D printer

“…Finally, we will demonstrate the proposed holographic optical-phased-array-based pixel architecture to implement a true single-shot volumetric 3D printing system, heterogeneously integrated with a co-designed CMOS electronics chip 30 , 33 , 34 , thus enabling solidification of entire 3D objects at once using a hand-held printer. In tandem with future iterations of the chip, we will also modify the visible-light-curable resins for compatibility with holographic 3D printing; specifically, we will work towards resins with decreased absorption and increased viscosity that operate via two-photon absorption 67 . Together, these additional innovations to both the chip and the resins will allow us to demonstrate the complete volumetric chip-based 3D printer vision.…”

Supramolecular Annihilator with DPA Parallelly Arranged by Multiple Hydrogen-Bonding Interactions for Enhanced Triplet–Triplet Annihilation Upconversion

“…There are several mechanisms to achieve UC emissions, such as multistep excitation of lanthanides ions [1], two-photon absorption [2], and second-harmonic generation [3], among which UC based on triplet-triplet annihilation (TTA) [4][5][6][7] is attracting continuous attention due to its unique advantages of tunable excitation wavelengths and high quantum efficiency. Thus, this has wide application potentials, ranging from photocatalysis [8,9], bio-imaging and bio-sensing [10][11][12][13], and drug release [14,15], to 3D printing [16,17]. The triplet sensitizer and annihilator are the essential components for TTA-UC, and a diagram illustrating the mechanism of TTA-UC is shown in Figure S1, in which the triplet-triplet energy transfer (TTET) process from the sensitizer to the annihilator and triplet-triplet annihilation (TTA) between the triplet annihilators are two pivotal processes for TTA-UC, both of which follow a Dexter mechanism.…”