Rapid and continuous 3-D printing with light

Rapid and continuous 3-D printing with light
(A) Optical setup for two-color SLA by concurrent photopolymerization and photoinhibition. Near UV (365 nm) is superimposed onto patterned blue (458 nm) with a dichroic mirror and projected through a transparent window into a photopolymerizable resin vat. Structures of (B) photoinitiator CQ, (C) co-initiator EDAB, and (D) photoinhibitor o-Cl-HABI. (E) UV-visible spectra of CQ (solid blue line) and o-Cl-HABI (dashed violet line) in tetrahydrofuran (THF). The UV and blue wavelengths used by the two-color AM system are highlighted by the violet and blue vertical bars, respectively. (F) Solid block M (left) and tug boat [model detailed in (31)] (right) printed using the two-color photopolymerization/photoinhibition stereolithography system at 500 and 375 mm/hour, respectively. (G) The polymerization inhibition volume thickness is affected by varying intensity ratios of the incident irradiation wavelengths (IUV,0/Iblue,0) and resin absorbance (hUV). Credit: Science Advances, doi: 10.1126/sciadv.aau8723
Three-dimensional (3-D) printing, also known as additive manufacturing (AM), can transform a material layer by layer to build an object of interest. 3-D printing is not a new concept since stereolithography printers have existed since the 1980s. The widespread availability and cost-effectiveness of the technology have allowed a variety of modern applications in biomedical engineering.

The contemporary process of layer-wise additive manufacture is nevertheless slow and impacts the rate of object fabrication for objects with ridged surfaces. Continuous stereolithographic printing can overcome the limits by increasing print speeds to generate objects with smooth surfaces. Now writing in Science Advances, Martin P. de Beer, Harry L. van der Laan, and co-workers demonstrate a new method for rapid and continuous stereolithographic additive manufacture (SLA) in a single shot by interfacing the raw material with two wavelengths of light.

The materials scientists developed a method using two sources of light; one to solidify the resin and another ultraviolet light to prevent resin curing on the device window during object fabrication. A zone without unwanted solidification (inhibition volumes) allowed efficient use of resins and boosted the speed of 3-D printing in a single exposure, in contrast to layer-wise, conventional manufacture. A variety of materials, including thermoplastics, polymer resins, and inorganic powders have been used as media for additive manufacture (AM), with a variety of methods including material extrusion, to powder bed fusion and binder jetting. In particular, stereolithographic AM (SLA) was of interest in the study since it is based on a patterned illumination source to cure cross-sections of the desired geometry.

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Image courtesy of phys.org