Fig. 4
Elastomeric, strain-actuated microfluidic purge system. a Demonstration of strain-induced suction in a serpentine microchannel embedded in PDMS to induce flow of a liquid dye (ΔV = change in volume). Scale bar: 1 cm. b 3D finite-element analysis of embedded microchannels with a cross section of 500 × 250 µm after straining to 50% indicates a capability to extract 44 µl of liquid. c Volume extraction as a percentage of initial pump volume and dependence on cross-sectional dimensions. d Total volume extracted and dependence on cross-sectional dimensions. e Volume extracted from the collection channel during multi-cycles straining of a resettable device. Covering the outlet hole and applying lateral strain to the pull tab extracts sweat. Uncovering the outlet and subsequently releasing the strain purges the sweat from the device via the outlet. f Collected sweat in a resettable epifluidic device. Scale bar: 1 cm. g Covering the outlet and extending the pull tab extracts sweat into the pump channel. Inset: Strain distribution during 100% strain of the pull tab (7.75 mm lateral deformation). h Uncovering the pump outlet and releasing the strain purges the extracted sweat via the pump outlet.
