Figure 1.
Live Collembola and their cuticle structure.
(a) Several specimens of Onychiurus sp., the scale bar is 1 mm. (b) SEM image showing the cuticle structure of Onychiurus sp.. A pattern of large, secondary granules (solid arrow) are shown and in between these a pattern of small, primary granules (dashed arrow), the primary granules are connected by ridges.
Figure 2.
Scanning Electron Microscopy (SEM) images of species 10 and 12.
Left: species 10 A. laricis Right: species 12 X. maritima. The images, at 10 000X magnification, show structures typical for the dorsal metasoma. Species 12 has a typical structure of triangular granules, connected by ridges, organized in a hexagonal pattern. Species 10 has markedly enlarged granules, in a variation of forms, organized in a varied pattern closer to square than hexagonal.
Table 1.
Contact Angle Measurement.
Figure 3.
SEM images of FIB cross sections of species 10 and 12.
Left: species 10 A. laricis magnification 8 000X, Right: species 12 X. maritima 15 000X magnification. The images show sections of the cuticle where a prism shaped part has been removed by FIB milling, while the structuring around it was protected by a layer of platinum, to reveal cross sections of the granules. A single granule is highlighted by a white circle in each image. In species 10 there is no evidence of overhang, in species 12 overhang is present.
Table 2.
Surface Structure Characteristics.
Figure 4.
Measurement of structural parameters.
The schematic shows how the structural parameters ,
,
,
,
and
were measured from SEM images.
Figure 5.
Measured contact angles compared to predicted contact angles.
Measured advancing () and receding (
) contact angles with one standard deviation error bars as compared to the values predicted by the Wenzel (
), Cassie-Baxter (
) and the Choi (
) equations. The minimum limit for contact angles considered superhydrophobic is denoted by a dotted line at
. Rows marked with an asterisk (*) denote predicted values based on secondary granules.
Figure 6.
Measured contact angles hysteresis compared to contact angle hysteresis predicted by the Dufour method.
The maximum limit for contact angle hysteresis considered superhydrophobic is denoted by a dotted line at . Rows marked with an asterisk (*) denote predicted values based on secondary granules.
Table 3.
Calculated Parameters.
Figure 7.
The contact angle is defined as the angle between the droplet, and the substrate at the contact line. The receding contact angle
is the contact angle for a droplet with a receding contact line, e.g. for a shrinking droplet, while the advancing contact angle
is the contact angle for an advancing contact line, e.g. a growing droplet. Surfaces that when in contact with water display a contact angle of less than
are hydrophilic, surfaces with contact angles of more than
are hydrophobic and surfaces with both advancing and receding contact angles of more than
as well as contact angle hysteresis less than
are superhydrophobic. The inset shows a sessile droplet in contact with a springtail.