Contacting solid-state image sensors can
be used for a wide range of applications, well beyond their original
purpose of fingerprint capture [1-3]. This research used a Fujitsu
MBF200 sensor of 12.8 x 15mm active area and 50 x 50 µm spatial
resolution. Each pixel is a fringing field capacitor whose capacitance
value depends on the dielectric constant of the sample material
in contact with it. Capacitance images of 8-bit greyscale resolution
can be captured at rates up to 10 images per second using a USB
connection to a PC.
The sensor was used to study solvent penetration into in-vivo
skin. A small amount of solvent was applied to volar forearm skin
for a predetermined time. After wiping dry, tape stripping was
performed. Contact images were captured before and after solvent
application, and after each strip. With DMSO and Glycerol, the
images show clear contrast between the solvent and normal skin
due to differences of dielectric constant. The results show that
DMSO penetrated deeper than Glycerol, as traces of DMSO were found
to be still visible after 10 strips, whereas Glycerol residues
were found to have disappeared after only 5 strips. The strip sequence
images can be analysed further to yield spatially resolved solvent
concentration depth profiles that reveal skin heterogeneity effects.
1. Leveque, J.L. and Querleux, B. SkinChip,
a new tool for investigating the skin surface in vivo.
Skin Research and Technology 9: 343-347
(2003).
2. Batisse, D., Giron F. and Leveque J.L. Capacitance
imaging of the skin surface. Skin Research and Technology 12:
99-104 (2006).
3. P Xiao, H Singh, X Zheng, E P Berg and R E Imhof, In-vivo
Skin Imaging For Hydration and Micro Relief Measurements. Stratum
Corneum V Conference, July 11-13, Cardiff, UK, 2007.
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