Solderable Multisided Metal Patterns Enables 3D Integrable Direct Laser Written Polymer MEMS

Advancing highly integrated micro sensors and actuators calls for the ability to scale down three-dimensional structures while ensuring efficient electrical interconnectivity. This necessitates addressing a pressing need to develop novel techniques for shrinking components and facilitating seamless interconnectivity to the miniature structures. Here, we demonstrate a three-step fabrication method to produce 3D prints fabricated by direct laser writing (DLW) via two-photon polymerization (TPP), with multisided evaporated metal patterns. The three steps consist of printing the core structure and shadow mask shell (SMS) on sacrificial Dextran 70, evaporating metal onto the desired side(s), and then releasing the core and SMS in water. To showcase this process’ capabilities, we produced a simple characterization structure featuring two electrical vias, an out-of-plane serpentine resistor, and four solderable electrodes. With this test structure, three firsts were achieved for the TPP community: (1) The deposition of metal patterns onto opposing sides of a DLW structure; (2) the flip-chip soldering of said structure to a PCB; and (3) the verification of electrical continuity through its two microvias.