Atto plasma cleaner

GPTMS coated glass substrates were prepared by cleaning glass coverslips (diameter 15 mm) in chloroform, isopropanol and water in a sonication bath for 5 min, respectively. The coverslips were dried by N₂ and activated by oxygen plasma treatment (0.2 mbar, 100% O₂, 100 W, 2 min, Atto plasma cleaner, Diener electronic, Ebhausen, Germany). Following this, the coverslips were placed into 1% v/v GPTMS [(3-Glycidyloxypropyl) trimethoxysilane] Toluene solution for 4 h. The silanized glass was washed with deionized (DI) water, then acetone and finally dried with N₂. Coverslips used as control substrates were stored in a desiccator prior to experiments. All chemicals were purchased from Sigma Aldrich, Germany.

We adapted the procedure described by Park et al. [47 (link)]. Briefly, glass slides were first rinsed with 2-propanol and dried using compressed nitrogen (N₂). Around 1.5 mL of AZ 1518 photoresist was drop-casted and a 1.8 µm layer was spin-coated at 4000 rpm for 30 s, followed by a solvent prebaking step at 100 °C for 50 s according to the manufacturer. The designed and laser-printed electrode pattern (Koenen GmbH, Hohenbrunn, Germany) was placed on the spin-coated substrates and exposed at 415 nm for 45 s (exposure dose of 16 mJ·cm⁻¹) using a mercury lamp of type Superlite S 04 (Lumatec, Oberhaching, Germany). The exposed slides were developed in AZ 351B for 15 s, rinsed with distilled water, dried with compressed N₂, and post-baked for 1 min at 115 °C. The developed slides were further subjected to 2 min atmospheric plasma (Atto Plasmacleaner, Diener Electronic, Ebhausen, Germany) followed by drop-casting 10 µL Galinstan and using a glass vial to roller-blade it on the pattern. The Galinstan-coated slides were then left in an acetone bath for 30 min to lift-off the excess Galinstan and photoresist. An amount of 400 mM W salt solution was added on top of the Galinstan pattern and left to react for 24 h, followed by rinsing with distilled water and drying with compressed N₂.