Three-Dimensional Metal Microprinting Based on Controlled Removal of Self-Assembled Monolayers
Coating and Surface Technology
Mechanical Process Engineering
Physical Chemistry of Solids and Surfaces, Material Characterisation
Final Report Abstract
This project was dedicated to develop a novel 3D metal microprinting technique, which can fabricate defect-free micrometal components with higher efficiency than the current techniques. Two strategies were proposed to site-selectively remove the SAM and trigger the electrodeposition. The first strategy is to use micro droplets or meniscus containing suitable reactant to remove the SAM, whereas the second is adopting laser. According to our proposal, the droplets need to be dispended and manipulated in liquid environments. However, most of the current droplets dispensing techniques, such as inkjet printing, can only works in gaseous environments. Therefore, we developed several different new methodologies for dispensing the micro droplets in liquid environments. The first method utilizes the break-up of a liquid meniscus between two equivalent orifices. We found that the break-up of a liquid meniscus always results in the formation of one or several satellite droplets which are much smaller than the feature size of the meniscus. The radius of the dispensed droplets can be 30 times smaller than the radius of the orifice, which allows the generation of micrometer-sized droplets from millimeter-sized orifices. In addition, liquids with viscosities larger than 1000 mPa s can be handled. The proposed method is expected to promote new developments in dropon-demand (DOD) devices for dosing reactive and viscous solutions, emulsions and suspensions or for releasing individual droplets to be used as small reactors. The second method is using the traditional piezoelectric inkjet nozzle but with a totally different droplets dispensing mechanisms with that in gaseous environments. Femtoliter droplets arrays and patterns can be easily printed just by immersing the inkjet nozzle into a carrier liquid which is immiscible with the ink. The droplets pinch-off mechanism was investigated by combining high speed imaging with CFD simulations. The formation of daughter droplets is due to the breakup of the liquid column at the end the drainage phase during piezoelectrical-driven mother drop volume oscillations. It can be used in many applications which need precision dispensing, such as dosing valuable solution into microfluidic carrier streams, printing high resolution droplets patterns for chemical or biological analysis. Besides the above two droplet dispensing techniques in liquid environments, we also developed two droplet dispensing techniques in gaseous environments. The first one is the satellite droplet printing (SDP) technique. Compared to the traditional IJP, the printing resolution can be strongly improved by dispensing and manipulating droplets by a totally different mechanism. By using the same orifice size, the drop volume is reduced in SDP to only several femtoliters while the typical IJP drop volume is in the range of several ten picoliters and above. The second is the pneumatic conveying printing (PCP) technique. The droplets of PCP are generated by the shear action of the air stream, and the droplet-conveying process also can be performed by the same stream. During the pneumatic conveying printing, the pressure inside the pipeline is close to one standard atmospheric pressure and there is no significant pressure fluctuation. PCP technique offers a new harmless way for printing of biological cells, which is applicable to different cell types. We have demonstrated that a focused laser is capable of site-selectively removing the SAM and trigging the electrodeposition. Micro metal columns with size consistent with the size of the laser would growth on the electrode surface in the direction of the laser, indicating the feasibility of the proposed principle. More work regarding the SAM removal mechanisms, electrodeposition mechanisms is needed for finally developing the 3D metal micro printing technique initially proposed.
Publications
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Generating ultra-small droplets based on a double-orifice technique. Sensors and Actuators B: Chemical 2018, 255, 2011-2017
Y. Zhang, B. Zhu, G. Wittstock, D. Li, Y. Liu, X. Zhang
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Inkjet Printing in Liquid Environments. Small, 2018, 14(27), 1801212
Y. Zhang, D. Li, Y. Liu, G. Wittstock
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Printing with satellite droplets. Small 2018, 14(39), 1802583
Y. Zhang, D. Li, Y. Liu, G. Wittstock
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Pneumatic conveying printing technique for bioprinting applications. RSC Adv., 2019, 9, 40910
I. Brand, I. Groß, D. Li, Y. Zhang, A. U. Bräuer
