Quantitative study of mass transfer in megasonic micro electroforming based on mass transfer coefficient: Simulation and experimental validation

Zhao, Ming; Du, Liqun; Du, Chengquan; Wei, Zhuangzhuang; Ji, Xuechao; Zhang, Bai; Liu, Xuqiang

doi:10.1016/j.electacta.2018.12.018

Cited by 25 publications

(9 citation statements)

References 32 publications

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“…Voids were found in the core of the microstructures with lateral feature sizes smaller than 70 µm, due to a restricted mass transfer in the microcavities of the mold. However, it is believed that microstructures with finer feature sizes and higher aspect ratios can be achieved by further improvements in microscale mass transfer, such as ultrasonic microelectroforming [35], jet electrodeposition [36], microelectroforming under boiling conditions [37], and pulsed current microelectroforming [38].…”

Section: Feature Sizementioning

confidence: 99%

Microelectroforming of freestanding metallic microcomponents using silver-coated poly(dimethylsiloxane) molds

Zhou¹,

Su²,

Li³

2020

J. Micromech. Microeng.

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Microelectroforming is not only a key step of LIGA (Lithographie, Galvanoformung, and Abformung) and LIGA-like techniques, but also a widely used method for fabricating freestanding metallic microcomponents. Currently, the commonly used molds, consisting of photoresist microstructures which are prepared by lithographic techniques and conductive substrates, limit the development of microelectroforming to a certain degree due to their high cost and complicated processing steps. In this paper, a novel low-cost and net-shaped microelectroforming method using silver (Ag)-coated poly(dimethylsiloxane) (PDMS) molds is demonstrated to fabricate freestanding metallic microcomponents. Pristine PDMS molds are first replicated from a microstructured master using soft lithography. Then polydopamine is adhered to the surfaces of the pristine PDMS molds and followed by electroless deposition of Ag nanoparticle coatings. Subsequently, metal atoms are electrodeposited on the Ag-coated PDMS molds to form metallic microcomponents. After microelectroforming, the Ag coatings are peeled off from the molds and adhered to the surfaces of the metallic microcomponents during the demolding process. However, the molds can be repaired repeatedly using electroless deposition of Ag coatings on the polydopamine films, and the Ag coatings adhered to the surfaces of metallic microcomponents can be completely removed by immersion in ammonia water. Therefore, the Ag-coated PDMS molds can be reused several times. The application of this method for fabricating freestanding metallic microcomponents is demonstrated by producing nickel microcomponents. The results show that freestanding nickel microcomponents with precise dimensions and low surface roughnesses can be reliably achieved. We believe that this method has great potential for fabricating metallic microcomponents, microparts, and micropatterns.

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Section: Feature Sizementioning

confidence: 99%

Microelectroforming of freestanding metallic microcomponents using silver-coated poly(dimethylsiloxane) molds

Zhou¹,

Su²,

Li³

2020

J. Micromech. Microeng.

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“…Nevertheless, the formability of microelectroforming is usually restricted by the limited mass transfer in the high-aspect-ratio microcavities of molds [7,8]. Extensive studies have been conducted to improve the mass transfer in the microelectroforming process, such as adding external fields [9][10][11] and changing the current waveform [12,13]. The enhancement effect of these methods decreases with the increase of the aspect ratio of the microstructures, and they have little influence on the mass transfer when the aspect ratio of microcavities is greater than 5 [11,14].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of high-aspect-ratio metallic microstructures by microelectroforming using silver-coated polydimethylsiloxane molds with controllable wettability

Zhou,

Xie,

Wang

et al. 2024

J. Micromech. Microeng.

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Microelectroforming is a specialized electroplating process to prepare functional metallic microstructures. However, the formability of microelectroforming is usually restricted by the limited mass transfer in high-aspect-ratio microcavities of molds. This paper presents a simple and reliable method utilizing silver (Ag)-coated polydimethylsiloxane (PDMS) molds with controllable wettability to enhance the formability of microelectroforming. The surfaces of these molds exhibited reversible water contact angles ranging from 4° to 151° realized through ultraviolet irradiation and heat treatment. The hydrophilicity of the PDMS molds facilitated liquid-phase mass transfer, contributing to the fabrication of complete and defect-free nickel microstructures with high aspect ratios. Subsequently, the hydrophobic PDMS molds reduced the interfacial adhesion between these molds and nickel microstructures, which was beneficial for perfect demolding. Nickel microstructures with an aspect ratio of 10 can be achieved by using the PDMS molds, which significantly enhance the formability of microelectroforming. This method provides a potential method to prepare high-aspect-ratio metallic microstructures.

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“…The study demonstrates that mass transfer in the micro/ nano cavity is mainly by diffusion and internal vortex flow, and as the width decreases from 2.5 to 0.5 mm, fewer streamlines enter the region near the inlet. Zhao 14 quantitatively studied the mass transfer during megasonic (1 MHz) micro electroforming. The simulation results show that as the aspect ratio of the microchannel increases from 1 : 5 to 5 : 1, the corresponding mass transfer coefficient which is a diffusion rate constant related to the mass transfer rate decreases by an order of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Electrodeposition model with dynamic ion diffusion coefficients for predicting void defects in electroformed microcolumn arrays

Jiang

Dong

et al. 2023

Phys. Chem. Chem. Phys.

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Quantitative study of mass transfer in megasonic micro electroforming based on mass transfer coefficient: Simulation and experimental validation

Cited by 25 publications

References 32 publications

Microelectroforming of freestanding metallic microcomponents using silver-coated poly(dimethylsiloxane) molds

Microelectroforming of freestanding metallic microcomponents using silver-coated poly(dimethylsiloxane) molds

Fabrication of high-aspect-ratio metallic microstructures by microelectroforming using silver-coated polydimethylsiloxane molds with controllable wettability

Electrodeposition model with dynamic ion diffusion coefficients for predicting void defects in electroformed microcolumn arrays

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