Single-Droplet Multiplex Bioassay on a Robust and Stretchable Extreme Wetting Substrate through Vacuum-Based Droplet Manipulation

Constraints on droplet dispensing

A repellent surface can help move a sample with little retention, but an assay also needs liquid to remain at selected locations. Transport and dispensing therefore impose different requirements. The study combines these functions for liquids whose surface tension or viscosity complicates manipulation.

Deformable substrates and selective wetting

The vacuum tip does not aspirate the liquid. It deforms PDMS from below to create a moving local dimple. Droplets travel over the weakly adhesive SPO region, while SPI wettable patterns retain part of the liquid. Separating transport from retention makes pattern size and liquid properties relevant to dispensing, rather than vacuum settings alone.

Dispensing and colorimetric assessment

Dispensing was evaluated by changing wettable-pattern diameter and measuring retained daughter droplets. The assay adds another sequence: enzyme and color reagents are deposited and dried first, sample aliquots are dispensed onto those zones, and the developed color is scanned. Successful droplet motion alone therefore does not establish assay performance; reagent placement, reaction, drying and image readout also matter.

Aliquot volumes and metabolite readout

For 1–2 mm patterns, water daughter droplets ranged from 0.05 to 1 μL; this is not the total starting-sample volume. Separate glucose, uric-acid and lactate zones enabled multiple colorimetric readouts. Glucose in mouse-derived samples was also compared with a meter. These results support integration of dispensing and assay zones, within the tested samples and workflow.

Boundaries of diagnostic interpretation

The mouse-sample comparison does not establish human diagnostic validity. The main text and Methods use different plasma/sera terminology, so this account keeps the sample description neutral. Supplementary information on device details, evaporation and storage stability is outside its scope, leaving deployment and sample-preservation conditions unresolved.

Some target concentrations in Table 1 differ from the values displayed in Fig. 5e. The reported error bound should therefore not be applied uniformly to every analyte.

Different uses of droplet arrays

The related droplet-microarray study examines suspension-cell treatment and imaging. Its samples, timing and endpoints differ from metabolite colorimetry. The abstract-level connection concerns droplet arrays; small volume alone cannot support a comparison of efficiency or accuracy.