Glass-Channel Molding Assisted 3D Printing of Metallic Microstructures Enabled by Femtosecond Laser Internal Processing and Microfluidic Electroless Plating

3D printing of metallic microstructures is highly desirable for many practical applications such as microelectronics, terahertz photonics, microelectromechanical systems, and electrochemisty. Unfortunately, high resolution microprinting of 3D metal structures with widely tunable feature sizes, high conductivities, high melting points, and highly smooth surfaces remains challenging for current microfabrication technologies. Herein, 3D printing of metallic microstructures of feature sizes ranging from ≈10 to ≈200 μm by combining femtosecond laser micromachining of 3D glass microchannels and microfluidic electroless plating is demonstrated. The proposed technique allows for producing 3D metallic structures of almost arbitrary geometries embedded in glass since the continuous flow of the plating solution enables controllable deposition of metal films inside the through microchannels. Moreover, freestanding metallic 3D microstructures are fabricated by removing the glass matrix with a wet chemical etching. As a nonthermal processing, the surface roughness of the fabricated metallic structures is as low as ≈20 nm. The 3D microstructures can be made of either silver or copper covered with a thin layer of silver, which are shown to have a high conductivity. As a proof-of-concept demonstration, a 3D metal scaffold structure with a size of ≈5 × 5 × 2 mm³ is printed.