Metal additive manufacturing for microelectromechanical systems: Titanium alloy (Ti-6Al-4V)-based nanopositioning flexure fabricated by electron beam melting

Three dimensional printing (3D printing) or additive manufacturing is a promising approach for construction of small-sized, complex structures in microelectromechanical systems (MEMS). This paper reports the design, fabrication and testing of an XY nanopositioning flexure made up of Titanium alloy (Ti-6Al-4V) created for the first time through electron beam melting (EBM), also known as electron beam additive manufacturing (EBAM). Titanium alloys present attractive characteristics including high biocompatibility, distinct strength and corrosion resistance. However, it has been difficult to machine titanium alloys through conventional processes. The use of additive manufacturing has enabled us to build a multidimensional nanopositioning flexure with amplified mechanical displacement and improved bandwidth contained in a compact structure. We first characterized mechanical properties of EBM-printed Ti-6Al-4V cantilevers and compared the results with those of bulk metal cantilevers. Due to the porous surfaces, the printed cantilevers acted as a softer material with an averaged Young's modulus of 41 GPa when considering only the outermost dimensions. By introducing inner widths of 0.51-0.53 mm for the CAD-designed beam width of 0.7 mm, we calculated a Young's modulus of 90-120 GPa, which is comparable to 108-120 GPa reported in literature for bulk Ti-6Al-4V. With the completion of the initial characterization, fabrication of the flexure was then undergone and successfully carried out. Mechanical levers printed within the flexure amplified an actuation from a piezoelectric actuator by a factor of six to displace a positioning platform supported by the network of parallel supporting beams. The maximum displacement of 47.4 mu m was obtained at the driving voltage of 150 V. The resonant frequencies measured for the x and y axes were almost identical 1854 Hz and 1858 Hz, respectively. A digital PID controller enabled laser-based dynamic positioning of the stage. For triangular sweeps at 16 Hz and 122 Hz, the positioning error was within 200 nm and 500 nm with time delays of 0.85 ms and 2.48 ms, respectively. (C) 2016 Elsevier B.V. All rights reserved.