Digital light processing in a hybrid atomic force microscope: In Situ, nanoscale characterization of the printing process

Higgins, Callie I.; Brown, Tobin E.; Killgore, Jason P.

doi:10.1016/j.addma.2020.101744

Cited by 9 publications

(7 citation statements)

References 23 publications

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“…One should note that the polymerization is not homogenous within the bulk, as the radiation decays exponentially from the surface to the inner part of the material (see Equation (8)) [ 43 ]. Therefore, the degree of polymerization is not the same on the two sides of the polymerized layer, the bottom side (which is directly exposed to radiation) and the top side; the difference generally depends on the thickness.…”

Section: Resultsmentioning

confidence: 99%

“…Gong et al [ 39 ] developed a mathematical model for optical dose (irradiance × time) delivered as a function of cure depth, including voids for microfluidic applications. Further, in-situ characterization techniques are reported, such as ultrasonic imaging [ 40 , 41 , 42 ], atomic force microscopy [ 43 ], and FTIR spectroscopy [ 44 , 45 ] for real-time prediction of polymerization and quick optimization of parameters before printing with polymer-based additive manufacturing.…”

Section: Introductionmentioning

confidence: 99%

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Rational Design and Characterization of Materials for Optimized Additive Manufacturing by Digital Light Processing

Chaudhary

Akbari²,

Antonini³

2023

Polymers

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Additive manufacturing technologies are developed and utilized to manufacture complex, lightweight, functional, and non-functional components with optimized material consumption. Among them, vat polymerization-based digital light processing (DLP) exploits the polymerization of photocurable resins in the layer-by-layer production of three-dimensional objects. With the rapid growth of the technology in the last few years, DLP requires a rational design framework for printing process optimization based on the specific material and printer characteristics. In this work, we investigate the curing of pure photopolymers, as well as ceramic and metal suspensions, to characterize the material properties relevant to the printing process, such as penetration depth and critical energy. Based on the theoretical framework offered by the Beer–Lambert law for absorption and on experimental results, we define a printing space that can be used to rationally design new materials and optimize the printing process using digital light processing. The proposed methodology enables printing optimization for any material and printer combination, based on simple preliminary material characterization tests to define the printing space. Also, this methodology can be generalized and applied to other vat polymerization technologies.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rational Design and Characterization of Materials for Optimized Additive Manufacturing by Digital Light Processing

Chaudhary

Akbari²,

Antonini³

2023

Polymers

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“…To accomplish this, we employed a custom-built instrument (Figure S5), where a spatial light modulator (SLM) is used to selectively direct light from a 405 nm LED to the sample plane of an AFM. 14 This selective illumination from below can be used to create light patterns that are used in DLP and allows for in situ interrogation during photopolymerization. The test requires only a few microliters of resin, which could dramatically reduce the costs associated with novel resin formulation.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Having characterized the cantilever response to liquids of known viscosities, we turned to the spatially restricted digital light processing (DLP) exposure of a photopolymer resin. To accomplish this, we employed a custom-built instrument (Figure S5), where a spatial light modulator (SLM) is used to selectively direct light from a 405 nm LED to the sample plane of an AFM . This selective illumination from below can be used to create light patterns that are used in DLP and allows for in situ interrogation during photopolymerization.…”

Section: Resultsmentioning

confidence: 99%

“…AFM/SLA Photorheology and Photopolymerization. To perform in situ measurements of the photopolymerization reaction, a custom-built instrument 14 that enables simultaneous light patterning and AFM measurements was used (Figure S5). Briefly, 405 nm light (M405LP1, Thorlabs) is projected to the sample plane of an inverted optical microscope (Olympus PLN) via the side port.…”

Section: ■ Methodsmentioning

confidence: 99%

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Voxel-Scale Conversion Mapping Informs Intrinsic Resolution in Stereolithographic Additive Manufacturing

Brown

Malavé

Higgins

et al. 2020

ACS Appl. Polym. Mater.

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In high-resolution stereolithography, printed parts deviate significantly from the projected photomask because of the reaction complexity on the voxel scale. To better understand the reaction process, we have developed a technique to measure local photopolymerization rates using a nanocylinder-tipped atomic force microscope cantilever. The drag force experienced during cantilever oscillations can be correlated to the viscosity and extent of reaction. Fluid dynamics simulations show micrometer-scale measurement localization, and the resonance-based measurement allows submillisecond temporal resolution. In a thiol−ene resin exposed to patterned light, oligomer diffusion length scales are significant compared to the size of printed structures. Consequently, part resolution is dictated by the competition between polymerization and diffusion. Because of the radical polymerization mechanism, increasing the light intensity at a constant dose decreases the local conversion, even though the diffusion length decreases. In the case of printed test structures with features matching the measured diffusion lengths, increased light intensity causes increased geometric aberration from the projected mask. Overall, the results indicate a need for enhanced control over polymerization and diffusion to obtain dimensionally accurate and mechanically homogeneous parts.

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In-situ ultrasonic monitoring for Vat Photopolymerization

Vallabh

Zhang

Zhao

2022

Additive Manufacturing

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Digital light processing in a hybrid atomic force microscope: In Situ, nanoscale characterization of the printing process

Cited by 9 publications

References 23 publications

Rational Design and Characterization of Materials for Optimized Additive Manufacturing by Digital Light Processing

Rational Design and Characterization of Materials for Optimized Additive Manufacturing by Digital Light Processing

Voxel-Scale Conversion Mapping Informs Intrinsic Resolution in Stereolithographic Additive Manufacturing

In-situ ultrasonic monitoring for Vat Photopolymerization

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