Mold-free fabrication of 3D microfeatures using laser-induced shock pressure

This paper reports on the fabrication of microfeatures on metallic foils using laser-induced shock forming without the assistance of micromold patterns. A mold-free laser shock forming technique, Flexible Pad Laser Shock Forming (FPLSF) has been developed and demonstrated to fabricate near-spherical microcraters on thin copper foils through the laser-generated plasma shock inducing plastic deformation on the copper foil. It is found that the crater formation strongly depends on the laser energy fluence applied to ablate an ablative overlay which is on top of the copper foil for plasma shock generation. Microfeatures with deformation depth of 80 μm to130 μm and radius of 485 μm to 616 μm were formed on 25 μm thick copper foils for the laser fluence of 7.3 J/cm2 to 20 J/cm2 while using aluminum foil as the ablative overlay and silicone rubber as a flexible support instead of a micromold. Fabrication of crater arrays on copper foils was also demonstrated successfully.