Dendrite-joining of air-gap-separated PMMA substrates using ultrashort laser pulses

Abstract

We demonstrate joining polymethyl methacrylate (PMMA) substrates by a dendrite pattern of a quenched melt using ultrashort laser pulses. Laser pulses from a 250-fs fiber laser at a repetition rate of 1 MHz were focused at the interface of the two PMMA substrates with an air gap of approximately 14 μm and direct laser joining was accomplished between two pieces of PMMA. Melted PMMA from the laser-irradiated region spread within a gap between the substrates and dendrite morphology of the melt spread outside the direct laser irradiated area of square spiral contour and increased the joining strength. The joint strength was 11 MPa for tensile and 21 MPa for the shear stress. Ultrashort laser pulses are useful to directly join PMMA substrates using localized melting and resolidification with a gap between the substrates.