Fabrication and characterization of titanium-alloy 3D printed solenoid inductors and their sensor applications

Recent progress in 3D printing has brought many interests in developing functional devices in various applications by enabling the exploration of complex 3D structures. This paper presents the first fully metal printed standalone 3D solenoid microinductors using a high-power laser with a biocompatible Ti-alloy. Fine powder-based 6AL-4V Eli Titanium was directly printed using an automated gantry laser system with 60 µm resolution to form the inductors without any substrate. A substrate-less 10-turn solenoid as a testbed was printed out and characterized, and additional designs of 20 and 40 turn inductors were further explored. The wire of the inductor was designed to have a 700-micron square cross-section and a winding gap of 300 microns. The successfully fabricated 10-turn titanium-alloy solenoid inductor showed an average inductance of 130 nH, a low-frequency resistance of 0.8 ohms at 0.3 MHz, and a quality factor of 10.5 at 30 MHz respectively. Additional electrodeposition of copper to the 10-turn inductor demonstrated process compatibility with the conventional micromachining process. The standalone inductor printing method saves a significant volume from where the conventional substrate dimensions often take more than the volume of the device. Also, the standalone inductor can directly be used as a sensor device. Examples of force-displacement sensing applications were presented using the 10-turn and 19-turn round edge solenoid inductors.