Dry Etching with Nanoparticles: Formation of High Aspect‐Ratio Pores and Channels Using Magnetic Gold Nanoclusters

Abstract Methods for generating nanopores in substrates typically involve one or more wet‐etching steps. Here a fundamentally different approach to produce nanopores in sheet substrates under dry, ambient conditions, using nanosecond‐pulsed laser irradiation and magnetic gold nanoclusters (MGNCs) as the etching agents is described. Thermoplastic films (50–75 µm thickness) are coated with MGNCs then exposed to laser pulses with a coaxial magnetic field gradient, resulting in high‐aspect ratio channels with tapered cross sections as characterized by confocal fluorescence tomography. The dry‐etching process is applicable to a wide variety of substrates ranging from fluoropolymers to borosilicate glass, with etch rates in excess of 1 µm s^–1. Finite‐element modeling suggests that the absorption of laser pulses by MGNCs can produce temperature spikes of nearly 1000 °C, which is sufficient for generating photoacoustic responses that can drive particles into the medium, guided by magnetomotive force.