Evaporation of water in a microfluidic channel under magnetic field

TL;DR

This study demonstrates that applying a magnetic field significantly enhances water evaporation in microfluidic channels by affecting nuclear spin isomer populations, with up to 140% increase observed.

Contribution

It reveals a novel magnetic effect on water evaporation in microfluidics, linked to nuclear spin isomer dynamics, which was previously unexplored.

Findings

Magnetic field increases evaporation rate by up to 140%.

Magnetic influence alters ortho-para water vapor ratio.

Evaporation exceeds that in open beakers despite saturated atmosphere.

Abstract

The evaporation of drops of water placed at the center of long poly(methyl methacrylate) microfluidic channels with a rectangular cross section of 0.38 mm2 is studied by simultaneously monitoring the shapes of two samples, one is in a 300 mT magnetic field, the other is in no field. A magnetic enhancement of the evaporation rate of up to 140 % is observed, which can be understood by treating the ortho and para nuclear isomers of water vapor as quasi-independent gasses with an ortho:para ratio in fresh vapor close to 2:3. It would take much longer than the 2 - 4 h duration of an experiment in the channel, for the ratio to approach the 3:1 equilibrium value. Magnetic field influences evaporation rate by equalizing the isomeric populations in the vapor phase. The atmosphere in the channel is saturated with water vapor yet the evaporation rate far exceeds that in open beakers.