  Effects of substrate temperature, substrate wettability and particles
concentration are experimentally investigated for evaporation of a sessile
water droplet containing colloidal particles. Time-varying droplet shapes and
temperature of the liquid-gas interface are measured using high-speed
visualization and infrared thermography, respectively. The motion of the
particles inside the evaporating droplet is qualitatively visualized by an
optical microscope and profile of final particle deposit is measured by an
optical profilometer. On a non-heated hydrophilic substrate, a ring-like
deposit forms after the evaporation, as reported extensively in the literature;
while on a heated hydrophilic substrate, a thinner ring with an inner deposit
is reported in the present work. The latter is attributed to Marangoni
convection and recorded motion of the particles as well as measured temperature
gradient across the liquid-gas interface confirms this hypothesis. The thinning
of the ring scales with the substrate temperature and is reasoned to stronger
Marangoni convection at larger substrate temperature. In case of a non-heated
hydrophobic substrate, an inner deposit forms due to very early depinning of
the contact line. On the other hand, in case of a heated hydrophobic substrate,
the substrate heating as well as larger particle concentration helps in the
pinning of the contact line, which results in a thin ring with an inner
deposit. We propose a regime map for predicting three types of deposits namely,
ring, thin ring with inner deposit and inner deposit - for varying substrate
temperature, substrate wettability and particles concentration. A first-order
model corroborates the liquid-gas interface temperature measurements and
variation in the measured ring profile with the substrate temperature.
