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Issue 18, 2018
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Micro-droplet arrays for micro-compartmentalization using an air/water interface

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Here we present a water-in-air droplet platform for micro-compartmentalization for single molecule guided synthesis and analysis consisting of a flow-system hosting dense arrays of aqueous microdroplets on a glass surface surrounded by air. The droplets are formed in a few seconds by passing a waterfront over the array of hydrophilic spots surrounded by a hydrophobic coating, thus forming a micro-droplet array (MDA). The droplet volumes are tunable from approximately 50 femtoliter to 20 picoliter by adjusting the size of the hydrophilic spots. MDAs consisting of femtoliter volume droplets were stable for more than 24 hours in air at 37 °C in a reversibly sealed flow-system, thus allowing us to perform assays that require long incubations in the droplets. Using differently fluorescing liquids, it was further shown that droplets can be reformed on the same MDA several times by passing a new liquid plug over the surface, and that fluorescence from one reaction can be washed away with little to no carry-over, hence allowing for multistep reactions to be carried out on the system. The MDA created by an air/water interface supported digital immunoassays as was demonstrated by measuring the Aβ42 peptide in cerebrospinal fluid of Alzheimers patients and control patients. To demonstrate a two step droplet assay, first, histidine tagged peptides were expressed in the droplets and bound to the droplet-enclosed surface. Subsequently, the his-tagged peptides were detected using enzyme-conjugated antibodies in a second droplet generation step. As such, the chip demonstrates features necessary for library preparations for high throughput screening applications.

Graphical abstract: Micro-droplet arrays for micro-compartmentalization using an air/water interface

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Supplementary files

Article information

14 Jun 2018
10 Aug 2018
First published
13 Aug 2018

Lab Chip, 2018,18, 2797-2805
Article type

Micro-droplet arrays for micro-compartmentalization using an air/water interface

A. H. Kunding, L. L. Busk, H. Webb, H. W. Klafki, M. Otto, J. P. Kutter and M. Dufva, Lab Chip, 2018, 18, 2797
DOI: 10.1039/C8LC00608C

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