Depiction of (a) a droplet's shape at rest the change in its shape when it is subject to low frequency vibration. The particles that accumulate will stay at rest when the vibration ceased. When (b) an evacuation flow is generated, it will bring a microsphere of radius R located a distance x with velocity v p . This particle velocity is hydrodynamically dependent on the flow velocity v(x) corresponding to the non-uniform distribution of velocity profile at a radial distance from the droplet center.
Description of basic (left) and modified (right) wells created out of adhesive cut-out pieces on a glass slide. A cross-sectional view of the modified well is shown below. Deposition of droplet with suspended glass beads in each well followed by placement on a shaker vibrating at low frequency produces ring particle patterns.
Sequence of images (a) to (d) depicting the change in droplet shape as consequence of a paper wick inserted into the middle of the droplet. At various stages, changes to the contact angle and diameter of contact with the solid surface can be seen.
Measurements of diameter of liquid contact with the solid surface and contact angle at various times after the paper wick is inserted into the middle of the droplet. The former is normalized to the diameter at time = 0.
An example sequence of microscope high speed video images showing particles being drawn to the droplet center when a paper wick is inserted (a)–(b). At the later stages, the three phase contact line moves from the well edge towards the center of the droplet (c)–(d). This applies the well architecture shown on the left of Fig. 2.
An example sequence of microscope high speed video images showing particles being drawn to the droplet center when a paper wick is inserted (a)–(b). At the later stages, the three phase contact line moves from the center of the droplet to the edge of the well (c)–(d). This applies the well architecture shown on the left of Fig. 2.
Schematic depiction of (a) contact line developing from the edge of the well towards the droplet center, and (b) contact line developing from the droplet center towards the edge of the well.
Accumulation of glass beads in a ring after evacuation of liquid from the well architecture (right of Fig. 2).
The deposition of colored liquid (representative of an analyte) to fill only the region occupied by the accumulated beads in the modified well.
When an analyte is deposited to contact the patterned beads, it will be assumed to cover up to the diameter D of the bead ring (a). This gives a volume usage of V s . With the stepped surface architecture (b), the analyte volume V r can be taken to fill the width in the architecture d in an almost torus-like shape.
Plots of ratio of analyte volume usage expected with and without the stepped architecture for various values of d/D. It can be seen that there is significant reduction in the volume of analyte usage with the stepped architecture.
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