Solid Ethanol as a Renewable, Low-Toxicity, Electron-Beam Direct Write, and Biomedical Material.

3D ice lithography (3DIL) is an emerging direct-write technique that fabricates intricate 3D structures using frozen precursors. Here, we report the use of ethanol as a renewable and low-toxicity precursor for 3DIL, intended for the first time for the fabrication of intricate porous microstructures for in vitro and in vivo biomedical applications. The first nanoindentation analysis of 3DIL materials reveals mechanical properties (Young's modulus 2-4 GPa) comparable to biocompatible polymers. TEM shows that the material is an amorphous carbon that undergoes controlled graphitization under annealing at very high temperatures (1300°C). Due to its chemical composition, mechanical properties, and stability in water, cross-linked ethanol scaffolds support in vitro endothelial cell adhesion and proliferation with high confluency. Patterned neurostimulation electrodes implanted in mouse brains elicit no significant increase in astrocytic or microglial activation, indicating excellent in vivo biocompatibility. Additionally, we present for the first time the use of optically transparent substrates and the first patterning of neurostimulation electrodes using 3DIL. This study positions 3DIL using ethanol as a versatile, direct-write technique using renewable precursors to produce novel microdevices in biomedical engineering.