Open nanofluidic films with rapid transport and no analyte exchange for ultra-low sample volumes.

Moving to ultra-low (<100 nL) sample volumes presents numerous challenges, many of which can be resolved by implementation of open nanofluidic films. These nanofluidic films are fabricated using a hexagonal network of gold-coated open microchannels which capture all of the following innovative advantages: (1) sample volumes of <100 nL cm-2; (2) zero analyte exchange and loss with the film materials; (3) rapid and omni-directional wicking transport of >500 nL min-1 per square of film; (4) ultra-simple roll-to-roll fabrication; (5) stable and bio-compatible super-hydrophilicity for weeks in air by peptide surface modification. Validation includes both detailed in vitro characterization and in vivo validation with sweat transport from the human skin. Sampling times (skin-to-sensor) of <3 min were achieved, setting new benchmarks for the field of wearable sweat sensing. This work addresses significant challenges for sweat biosensing, or for any other nano-liter regime (<100 nL) fluid sampling and sensing application.