MicroAngelo Technique: 3D Sculpting of Nanofilms by Spatiotemporal Modulation of Thermocapillary Forces

With just a crude hammer and chisel at the age of 17, Michelangelo sculpted one of the most beautiful 3D marble reliefs ever known - the Madonna of the Steps. Its complex topography, with less than millimeter thickness variations, lends an awe inspiring quality to this masterpiece. Though not an aesthetic parallel, the photolithographic fabrication of today's integrated circuits also relies on complex topographic sculpting of nanofilms wherein light passed through a photomask engraves a pattern into photosensitive layers revealed after chemical treatment. Deep UV can yield feature sizes well below 100 nm, a true marvel as well. Here we present the theoretical foundations and experimental validation of a sculpting technique for contactless, one step patterning of nanofilms called MicroAngelo.This technique relies on spatiotemporal modulation of thermocapillary forces by projection of thermal distributions onto the gas/liquid or liquid/solid interface. Liquid is thereby drawn out-of-plane into desired 3D shapes by enormous surface forces that orient parallel to the moving boundary. The liquid film can track and replicate a moving patterned target until the final shape solidifies in-situ. Theoretical analysis will focus on predictions obtained from linear and weakly non-linear analysis, Lyapunov analysis, parametric resonance, nonlinear evolution, proximity corrections and resolution limits. Experimental analysis will focus on decades of effort by researchers worldwide in identifying the primary physical mechanism and subsequent successful fabrication of complex microlens arrays, linear waveguides, ring resonator shapes, and non-array intricate patterns. We believe these findings evidence the enormous potential inherent in this and alternative 3D microscale lithographic techniques based on film sculpting by powerful surface forces.