Taiwan: UV, Blue & Red Photo-Confinement in 3D Printing

IMTS

Share this Article

Taiwanese scientists are researching ways to overcome obstacles in photolithography, detailing their findings in the recently published paper, ‘3-Wavelength (UV, Blue, Red) Controlled Photo-Confinement for 3D-Printing: Kinetics and Modeling.’

Historically, photolithography has been limited in prototyping to fabrication of thin layers of material created via single wavelength light. To expand such techniques, the researchers explored two-color (UV and blue light), direct-write photolithography.

Currently, photopolymerization confinement (PC) is a common technique for continuous printing in additive manufacturing, offering a way to fabricate structures at high linear velocities, along with using only a single exposure.

Streamlined 3-Wavelength PC requires the following:

  • Photoinhibition light (UV)
  • Numerous, compatible monomers and co-initiators
  • Photoinhibition of free-radical chain-growth
  • Spatially confined, formulated resins
  • Elimination of inhibitor species in the dark or after UV exposure
  • Large polymerization inhibition depth adjacent to the projection window
  • Continuous part production

Schematics of photochemical pathways of a 3-wavelength photopolymerization, in which crosslinkers are formed via three pathways: the photoinitiator A (under a blue light), B (under a UV light), and oxygen-mediated C (under a red light). The initiation radicals R, [1O2] and [X] initiate the monomer [M] polymerization; whereas the inhibition radical [N] reduces the active radical R. Also shown is the co-initiator (D) which reacts with the triplet state of A (A*) forming an intermediate radical (R’) and a reactive radical (R), initiating crosslinkers; terminations may be resulted by the interaction among R’, R and [N]. The blue-light conversion could be enhanced by pre-irradiation of the red-light which reduces the oxygen-inhibition effect; whereas it could be reduced by the inhibitor [N], as a switch-off mechanism. Right hand side shows the couplings among R and (R’, N, M, 3O2), in which the oxygen inhibition is governed by the rate constant, k”.

“In dual-wavelength systems, the IT may be reduced by decreasing irradiation intensity and thus increase the print speeds as polymerization proceeds closer to the projection window,” stated the researchers. “For a given resin composition, the IT depends on the ratio of inhibitor to initiator absorbance, quantum yield of the radicals, reaction rates among the radicals and monomers, initiator, co-initiator and inhibitor, and the light intensity and dose (or exposure time).”

If the light is varied by pixel, the system can also complete topographical patterning on the surface with a single exposure layer. For a perpendicular scheme, photopolymerizations have been noted as confining ‘in depth the regional polymerized resin,’ with blue and UV lights causing respective polymerization initiation and inhibition.

Oxygen profiles under the irradiation of red-light only (left); blue and red light (right); but in the absence of UV-light (or B2=0 ), for various initial oxygen concentration of [O2]0=(0.5,1.0, 2.0, 4.0)%, for curve (1,2,3,4); and [A]0=[B]0 = 1%; B1=B3=0.05 (1/s/%); and rate constants (k,k’,k”,kT)= (8,1, 0.1,0.5) ((1/s). profiles of blue-light (without UV-light) for (left Figure) C10= (0.05, 0.1, 0.2, 0.4) %, for curve (1,2,3,4), for fixed b1=0.1 ; and (right Figure) b1=(0.015,0.05,0.15,0.5) , for fixed C10=0.2 %; for C30=0.5 %, [M]0 = 0.2%, k’ =1.0, kT=0.5 , k57= (k5/k7)=k68= (k6/k8)= k” = 35 (1/s).

Overall, the researchers realized that for an efficient PC, they required both a strong N-inhibition for uncured regime with a low conversion, and a weak S-inhibition for high conversion under either the blue light, or the blue- and red-light initiation.

A reverse feature was noted when [B] was higher than the transition value—leading to higher conversion as predicted by the research team’s formula:

“This is one of the new findings of this modeling study, which, however, requires further experimental justification,” stated the authors.

Conversion profiles (left) and H-function (right), under the irradiation of 2-light (blue and UV), without oxygen ([O2]0.=0) or the red-light (B3=0 ), for various initial concentration of [B]0 = (0, 0.5, 1.0, 3.0)1%, for curves (1,2,3,4); and for (B1, B2)= (0.05, 0.003), and [A]0 = 1%.

“Higher oxygen concentration leads to a lower conversion, which could be enhanced by reducing the S-inhibition via a red or blue-light pre-irradiation,” concluded the researchers. “The strategy for an efficient PC could be achieved by tailoring the two competing factors, N-inhibition and S-inhibition, independently via the steps of: (i) red-light pre-irradiation for minimal S-inhibition (oxygen-inhibition); and (ii) followed by a combined irradiation of UV and blue light, under the criterion for efficient PC to achieve reduced confinement depth, and high print speed.”

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘3-Wavelength (UV, Blue, Red) Controlled Photo-Confinement for 3D-Printing: Kinetics and Modeling’]

Share this Article


Recent News

3D Printing News Briefs, March 2, 2024: 3D Printed Firearms, FDA Clearance, & More

3D Printing Financials: Materialise Reports Growth in 2023 with Medical Segment Success



Categories

3D Design

3D Printed Art

3D Printed Food

3D Printed Guns


You May Also Like

3D Printing Financials: Xometry’s Year of Growth and Challenges

Finishing 2023 amid broader economic challenges that have troubled many in the 3D printing sector, Xometry (Nasdaq: XMTR) reported a solid 31% increase in the fourth quarter revenue, reaching $128...

3D Printing Financials: 3D Systems Misses Revenues by 9.32%, Targets 2027 for Clinical Human Lung Trials

In the latest financial unveiling, 3D Systems (NYSE: DDD) shared its fiscal report for the last quarter of 2023 and the entire year, shedding light on its struggles and strategic...

3D Printing Webinar and Event Roundup: February 25, 2024

It’s another busy week of webinars and events in the AM industry, including Silicone Expo Europe in Amsterdam, an open house for Massivit in North America, and the AM for...

Materialise Expands Jaw Surgeries with End-to-End Medical 3D Printing Treatment

Imagine the discomfort of experiencing pain every time you eat, or the constant radiating pain in your head due to this condition—it would be incredibly distressing. One reason why joint...