Comparative study on protocols to prepare slippery liquid-like PDMS coatings - pitfalls and time-savers

Slippery covalently attached liquid surfaces (SCALS, also called quasi-liquid surfaces, liquid-like surfaces, and slippery omniphobic covalently attached surfaces) have recently emerged as a new family of materials with many useful properties --- such as droplet-shedding, anti-icing, and anti-fouling --- and can serve as model systems in studies of wetting, evaporation, and self-assembly phenomena. They are made of nano-thin layers of polymers or oligomers that are liquid at ambient temperature and covalently attached to a smooth substrate. Herein we lay out protocols for preparation of the most common SCALS system: polydimethylsiloxane (PDMS) bound to silica surfaces via silane chemistry. The apparent simplicity of these layers and their methods of preparation is misleading, and obtaining reproducible results requires careful control of the reaction parameters. Exact details of the synthetic methods for SCALS determine the observed results, and reporting them is required for reproducibility and to advance understanding of the field. Here a range of synthetic methods used in the literature were reproduced in three different laboratories across the world, their comparative advantages and disadvantages discussed, and resulting SCALS characterised. For each synthetic method the key parameters that contribute to their performance and ease of reproducibility were identified and optimised.