  Polymer nanocomposite materials based on metallic nanowires are widely
investigated as transparent and flexible electrodes or as stretchable
conductors and dielectrics for biosensing. Here we show that Scanning
Dielectric Microscopy (SDM) can map the depth distribution of metallic
nanowires within the nanocomposites in a non-destructive way. This is achieved
by a quantitative analysis of sub-surface electrostatic force microscopy
measurements with finite-element numerical calculations. As an application we
determined the three-dimensional spatial distribution of around 50 nm diameter
silver nanowires in 100 - 250 nm thick gelatin films. The characterization is
done both under dry ambient conditions, where gelatin shows a relatively low
dielectric constant, epsilon around 5, and under humid ambient conditions,
where its dielectric constant increases up to epsilon around 14. The present
results show that SDM can be a valuable non-destructive subsurface
characterization technique for nanowire-based nanocomposite materials, which
can contribute to the optimization of these materials for applications in
fields such as wearable electronics, solar cell technologies or printable
electronics.
