Aluminum Hydroxide Nano- and Microstructures Fabricated Using Scanning Probe Lithography with KOH Ink

Abstract

Using scanning probe lithography (SPL) with KOH ink, this study fabricates aluminum hydroxide (Al(OH) 3 ) nano-and microfeatures on a gold (Au) film that has been deposited on an aluminum (Al) layer. Hydroxyl ions (OH − ) from the KOH ink loaded onto the Au film can react with the underlying Al layer to form Al(OH) 3 structures due to the decrease in the pH of the reacting solution. 1 In this process, Al(OH) 3 solidification is governed by the pH of the KOH ink solution, which is affected by its volume. Suitably small volumes (down to hundreds of attoliters) of the KOH ink solution can be applied to the substrate surface using dippen nanolithography (DPN) and polymer-pen lithography (PPL). Using DPN and PPL printing with the solid (i.e., gel) and liquid phases of KOH ink, sub-micron-(minimum ≈300 nm) and micron-sized (≥4 μm) Al(OH) 3 features can be obtained, respectively. The fabrication of Al(OH) 3 structures using the proposed pHdependent solidification process can be achieved with relatively small volumes in ambient conditions without requiring a previously reported molding process. 1,2

From Droplets to Devices: Recent Advances in Liquid Metal Droplet Enabled Electronics

“…Among many attractive properties of liquid metal droplets (LMDs)-high electrical and thermal conductivities, [46,47] low melting point, [48] low viscosity [1,2,[4][5][6] and negligible biotoxicity [2,12,[49][50][51] -the high reactivity of LMDs poses many promising applications. [13] Eutectic gallium indium (EGaIn), which consists of 85.8 wt% Ga and 14.2 wt% indium (In), and Galinstan, which consists of 78.3 wt% Ga, 14.9 wt% In, and 6.8 wt% tin (Sn) are two representative classes of liquid metals that are widely studied.…”

“…[1] An intriguing characteristic of these metals is their capability to form droplets, which opens up novel opportunities for their use in microscale and nanoscale applications. [2][3][4][5][6] Liquid metal droplets (LMDs) combine the advantageous properties of liquid metals with the benefits offered by their miniaturized form factor dominated by high surface tension, high mobility, and mechanical robustness. These include a high surface-to-volume ratio that enables functionalization, distinct rheological characteristics, and unique interactions with other materials.…”