  Solutions of macromolecules can undergo liquid-liquid phase separation to
form droplets with ultra-low surface tension. Droplets with such low surface
tension wet and spread over common surfaces such as test tubes and microscope
slides, complicating \textit{in vitro} experiments. Development of an universal
super-repellent surface for macromolecular droplets has remained elusive
because their ultra-low surface tension requires low surface energies.
Furthermore, nonwetting of droplets containing proteins poses additional
challenges because the surface must remain inert to a wide range of chemistries
presented by the various amino-acid side-chains at the droplet surface. Here,
we present a method to coat microscope slides with a thin transparent hydrogel
that exhibits complete dewetting (contact angles $\theta\approx180^\circ)$ and
minimal pinning of phase-separated droplets in aqueous solution. The hydrogel
is based on a swollen matrix of chemically crosslinked polyethylene glycol
diacrylate of molecular weight 12 kDa (PEGDA), and can be prepared with basic
chemistry lab equipment. The PEGDA hydrogel is a powerful tool for \textit{in
vitro} studies of weak interactions, dynamics, and internal organization of
phase-separated droplets in aqueous solutions.
