3D ice lithography and post-processing using gold organometallic precursor

3D ice lithography (3DIL) is an emerging method for fabricating polymeric 3D objects with submicrometer patterns. However, there are no studies on 3DIL using metal-containing precursors. In addition, unlike numerous post-processing studies of two-photon polymerization (2PP) and focused electron beam-induced deposition (FEBID), there are no 3DIL post-processing investigations. Here, we present a 3DIL process using an organometallic precursor (gold dimethyl acetylacetonate, Au(acac)Me 2 ), and its first post-processing study. We investigated 3D processing parameters and post-processing using Ar-, air annealing, and O 2 plasma. X-ray photoelectron spectroscopy (XPS), atomic force microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy were used for materials analysis. Our results show (i) 3DIL processed materials exhibit thermoset properties, as they decompose rather than melt at elevated temperatures; (ii) free metal atoms diffuse and form clusters, here, gold nanoparticles with a diameter of around 10 nm were formed; (iii) oxygen treatments remove carbon-based ligands while leaving noble metals behind. Also, Ar annealing leads to less material loss than air annealing, while O 2 plasma generates oxidized Au states and efficiently removes carbon ligands. Ar annealing at 600 °C reduces the carbon XPS signals significantly and increases the gold XPS signal by ten times, giving a good purification effect but with a high material removal of around 95%. We printed large Au metalorganic 3D structures (>1000 times larger volume than FEBID), which suggests 3DIL bridges the gap between the capabilities of 2PP and FEBID. The unique capabilities of organometallic compounds to detect environmental changes can position 3DIL for sensing applications, and 3DIL is a safe and non-toxic technique to manufacture nanoparticle-containing 3D structures, which may have applications in many fields such as nanophotonics, drug delivery, and catalysis.