We propose a novel process for locally fabricating free-form metal structures embedded in a fused silica mould. This process is based on micro-pressure infiltration principle that works as follows. First, a silica glass mold consisting on an arbitrarily-shaped 3D cavity is fabricated by femtosecond laser illumination and selective etching. Second, the mold and metal pellets that will form the infiltrant are heated up in a vacuum furnace. Once the metal melts and covers the open cavities entrance, a gas is fed into the furnace, pressurizing the metal-gas interface and resulting in the metal infiltration. After cooling down, the freeformed metal volume can be recovered by dissolving the molds or kept inside depending on the final applications. Here, we expand the flexibility of this process by replacing the furnace, by direct-laser heating of the metal combined with a localized pressurizing scheme, instead of applying the pressure on the whole substrate.

A cavity is fabricated by femtosecond laser illumination and subsequent chemical etching. At the bottom of the cavity, two channels having square cross-section are formed. The cavity is first filled with a pure copper powder then locally put under vacuum. A continuous-wave infrared laser is then used to heat the metal through the glass substrate. After melting the copper, the cavity is pressurized locally up to 5 bar. The process is observed dynamically with a CMOS-camera in the coaxial direction of the laser beam. The molten copper in the cavity was infiltrated in the channel. The infiltration speed is at least faster than 30 ms. In the filled area, the copper is homogeneous and no void were observed. The technique will be utilized for the study of the micro die casting process.