= Wilhelm Barthlott
{c}
= W. Barthlott
{c}
{synonym}
\b[W. Barthlott], or \b[Wilhelm Barthlott], investigated the structure and function of plant surfaces using <scanning electron microscopy>. His group connected microscopic surface features with water repellency and self-cleaning, giving the <lotus effect> an experimental basis and motivating technical surface designs.<Wilhelm Barthlott curriculum at Lotus-Salvinia>[Curriculum, plant-surface microscopy and research program]{ref}
With <C. Neinhuis>, Barthlott compared plant surfaces after adding particles and applying controlled artificial rinsing. The measured function was particle removal by rolling droplets, interpreted together with surface microrelief and water repellency.<Purity of the sacred lotus, or escape from contamination in biological surfaces by W. Barthlott and C. Neinhuis>[Abstract, contamination/rinsing experiment and mechanism]{ref} The later team interview describes how botanical observations motivated materials research rather than beginning from an already specified industrial design.<Unverschmutzbare Werkstoffe: Team 1 1998 by Deutscher Zukunftspreis>[interview, plant-surface microscopy and transfer to technical materials]{ref}
An original force-balance illustration explains why easy rolling matters. Model a droplet of mass $m$ on an inclined surface as having a fixed retention force $F_r$. Downhill motion can begin when $mg\sin\alpha>F_r$, where $\alpha$ is the tilt. For stipulated $m=10\,\mathrm{mg}$, $g=9.81\,\mathrm{m\,s^{-2}}$ and $F_r=20\,\mu\mathrm N$, the threshold is
$$
\alpha=\arcsin\!\left(\frac{20\times10^{-6}}{10^{-5}\times9.81}\right)\approx11.8^\circ.
$$
This simplified threshold is not a measured value for a lotus leaf. It shows that droplet mass and retention both affect motion; a high static <contact angle> alone does not supply the needed force balance. Real retention also depends on surface defects, droplet geometry and wetting history.
\Image[https://www.lotus-salvinia.de/images/DSCF0056.jpg]
{title=Wilhelm Barthlott, portrait linked from his individual Lotus-Salvinia research profile}
{width=240}
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