Contaminant Adhesion (Aerial/Ground Biofouling) on the
Skin of a Gecko
Gregory S. Watson, Bronwen W. Cribb, Lin Schwarzkopf, Jolanta A Watson
Supplementary Material
XPS characterization of the gecko
There were no clear differences between the three areas from the dorsal, ventral and head
areas of the gecko. Detailed scans of the N 1s region, Si 2s and 2p and S 2p and S 2s were
collected (figure S1). The spectra were corrected for charge shift, by taking the adventitious
C 1s component to be 284.6 eV. The binding energy for the N 1s peak was 399.8  0.2 eV.
That value is consistent with the N being part of an organic compound (e.g. keratin inorganic compounds give binding energies of 405-407 eV). Likewise the Si 2p binding
energy, 101.6  0.2 eV is consistent with it being organic because an oxide species would
have a binding energy of 103.8 eV. Finally, the S 2p binding energy, 163.70.2 eV is
consistent with it being part of an organic environment (because an oxide species would have
a binding energy in the range 166-169 eV). The S species is putatively present as a disulfide
bond that cross-links the fibres, while the N species is part of the fibre structure.
Supplementary Figures
Figure S1. Data obtained with the XPS which demonstrates a binding energy for the N1s
peak of 399.8 ± 0.2 eV. The S2p binding energy of 163.77 ± 0.2 eV is shown in the inset. The
scans were obtained on the skin surface of the gecko.
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Figure S2. Orientation of a gecko demonstrating the ability of the lizard to contort the body.
The heavily folded trough regions may potentially stretch (A) and fold (B) to accommodate
such movement of the lizard.
Figure S3. Photographs of insect species used as topographical comparisons to the gecko
skin: (a) Cicada, Tamasa tristigma; (b) Butterfly, Eurema hecabe; (c) Lacewing, Myrmeleon
acer; (d) Flower wasp, Scolia soror; and (e) Bladder Cicada, Cystoma saundersii.
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Figure S4. Photographs showing the gecko (Hemidactylus frenatus, an Asian House Gecko)
resting in an inverted horizontal (on ceiling) position (a) and a vertical wall (b). Both
positions demonstrate the gecko’s resting position with its underside in contact with the
surfaces in both positions thereby increasing its overall contact area.
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