Electrochemical mass transfer experiments are performed in a channel in which one wall is made of a soft polymer gel. Mass transfer is enhanced up to 25% relative to rigid walls when the ratio of viscous to elastic forces on the gel increases above a critical value. The enhancement is attributed to a hydrodynamic instability occurring at the fluid-gel interface. The results suggest that soft elastic boundaries could serve as a mechanism for improving mixing and transport in the laminar flows characteristic of microfluiclic devices and other small-scale geometries. (C) 2008 Elsevier Ltd. All rights reserved.