ALD MATERIALS

Editorial Feature

Michigan Team take control of 3D print colors by modifying inorganic films in ALD coatings

Recently, a new application for atomic layer deposition was reported by Neil Dasgupta and his research group in collaboration with the research groups of Prof. L. Jay Guo (Electrical Engineering & Computer Science) and Kira Barton (Mechanical Engineering), both of whom are at the University of Michigan, Ann Arbor.

In this study, they were able to change color patterns on the surface of 3D printings when ALD was used to adjust an inorganic film.

Nickel, zinc oxide, and a thin copper layer were used in this deposition, while the thickness adjustment was focused on the zinc oxide layer. With a thickness of 40 nm of ZnO, the 3D printed object showed a red color and, at 80 nm, a blue color.




Image from abstract: Integrating Structural Colors with Additive Manufacturing Using Atomic Layer Deposition, Benjamin A. Rorem, Tae H. Cho, Nazanin Farjam, Julia D. Lenef, Kira Barton, Neil P. Dasgupta, and L. Jay Guo, ACS Applied Materials & Interfaces 2022 14 (27), 31099-31108, DOI: 10.1021/acsami.2c05940


The advantage of this insight is that inorganic structures, such as ZnO, allow more stability in colors at elevated temperatures, which is not the case for conventional painting. They demonstrated the thermal stability of these structural colors at elevated temperatures (up to 300oC), where many polymeric paints would not survive. This enables application in harsh environments while maintaining the surface color of the object.

To achieve such, the University of Michigan team (Benjamin A. Rorem,  Tae H. Cho, Nazanin Farjam, Julia D. Lenef, Kira Barton, Neil P. Dasgupta, and L. Jay Guo),  printed multiple colors on a single sample using electrohydrodynamic jet (e-jet) printing. Afterward, they employed a metal-dielectric-metal (MDM) stack to enhance the vibrancy and purity of the color compared to simply coating a single ALD layer. The team also shows how this can be integrated with the printing of polymers for area-selective ALD (AS-ALD), leading to the "color printing" of AS-ALD materials.

According to Professor Dasgupta, this work demonstrates the power of using conformal ALD coatings to impart color onto 3-D printed surfaces and objects, permitting a precise tuning of the color of the printed surface across the visible spectrum, which can be easily adjusted by changing the thickness of the ALD coating.

Neil told us that ALD presents unique advantages for coating complex 3-D geometries with high aspect ratios, such as the non-planar topologies of metal 3-D printed objects. In contrast, traditional paints would have a difficult time infiltrating the micro/nanopores and topological features, especially at small length scales.

Professor Dasgupta also noted that the combination of ALD and 3-D printing is a powerful platform to enable the manufacturing of macroscopic 3-D objects with tunable surface properties, which may be different from those of the underlying bulk material.

When asked about the drawbacks and limitations of the technique, Neil affirmed that cost and throughput are always important considerations with ALD compared to other methods, so the appropriate selection of precursors and process conditions are essential variables to consider while ensuring manufacturability.
 
Professor Neil Dasgupta completed a B.S. in Mechanical Engineering from the University of Illinois at Urbana-Champaign in 2005, an M.S. in Civil and Environmental Engineering at Stanford University in 2006, and a Ph.D. in Mechanical Engineering with a minor in Materials Science and Engineering at Stanford University in 2011. He has been working in the area of ALD for advanced nanomanufacturing with an emphasis on applications in energy and sustainability for 17 years.




Professor Neil Dasgupta, image from Umich.


Currently, Neil is an Associate Professor and Miller Faculty Scholar,  Department of Mechanical Engineering and Department of Materials Science & Engineering, University of Michigan, where he leads a research group with 24 members, focusing on major research themes including next-generation batteries, solar energy, catalysis, bio-inspired materials, and nanomanufacturing.




Dasgupta Research Group, image from their group page.

 

According to Professor Dasgupta, a significant focus of his group in the coming years is focusing on scale-up and manufacturability. In particular, they are excited about their work in spatial ALD, which can enable high-throughput coating of surfaces in a continuous manner. Moreover, they also focus on low-cost and high-throughput processes to enable new uses of ALD beyond the traditional semiconductor applications.

References:


Integrating Structural Colors with Additive Manufacturing Using Atomic Layer Deposition, Benjamin A. Rorem, Tae H. Cho, Nazanin Farjam, Julia D. Lenef, Kira Barton, Neil P. Dasgupta, and L. Jay Guo, ACS Applied Materials & Interfaces 2022 14 (27), 31099-31108, DOI: 10.1021/acsami.2c05940


Professor Dasgupta group webpage: https://dasgupta.engin.umich.edu/people/current-members/


Collaborators' group webpages: http://www.guogroup.org/ and https://brg.engin.umich.edu/

 

Written by Tiago Belé

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