  Liquids serve microcavity research ever since Ashkins studies on optical
resonances in levitating droplets to recent optofluidic resonators. Droplets
can provide optical quality factor (Q) in proximity to the limit restricted by
water absorption and radiation loss. However, water micro-drops vaporize
quickly due to their large area to volume ratio. Here we fabricate a water-air
interface that almost entirely surrounds our device, allowing for more than
1,000,000 recirculations of light (finesse). We sustain the droplets for longer
than 16 hours using a nano-water-bridge that extends from the droplet to a
practically-unlimited distant-reservoir that compensates for evaporation. Our
device exhibits surface tension 8000-times stronger than gravity that
self-stabilizes its shape to a degree sufficient to maintain critical coupling
as well as to resolve split modes. Our device has 98 percents of their
surrounding walls made strictly of water-air interfaces with concave, convex or
saddle geometries, suggesting an arbitrary-shape microfluidic technology with
water-walls almost all-over.
