Laser Induced Forward Transfer-Based Micro-3D Printing of NiTi Alloy

Abstract

In this work, Laser-induced forward transfer (LIFT) is deployed for micro-3D printing to deposit NiTi alloy using CO2 laser (λ = 10.6 µm) in the form of the solid phase. The transparent silicon wafer (with laser wavelength) is used as the donor substrate and Polydimethylsiloxane (PDMS) as a sacrificial layer that absorbs the laser energy and induces a thrust force for the transfer mechanism. Over the sacrificial layer, NiTi alloy thin film is deposited with DC sputtering technique at working pressure 2 × 10–3 mbar and stand-off distance 5 cm. After the donor preparation, the micro-3D printing is deployed at laser fluences 1270 mJ/cm2 at different (100 mm, 130 mm, 160 mm) focusing distances from the lens (f = 100 mm). It is observed that due to the high energy density of the laser beam at 100 mm distance, the pixel gets ablated from the top surface while at 160 mm distance the energy is insufficient for the complete transfer. Then the spot overlap is varied with 30%, 60%, and 90%, and observed that with an increase in overlap % the pixel density increases leading to a continuous line pattern. The deposited geometry's surface morphology has been analyzed using a scanning electron microscope (SEM) and optical microscope. EDS is performed to confirm the elemental composition of the deposition and observed that Ni and Ti are nearly equal in wt % with Si, and C due to the dissociation of PDMS sacrificial layer. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.