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

Abstract

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.