  Rate of a reaction is enhanced by increase in temperature, partial pressure
or the concentration of reactants, and/or via use of a catalyst or an enzyme.
Whereas the former increases the probability of collision rate between
different molecules, the latter provides an alternate reaction path that
diminishes the activation energy barrier for reaction, both effects increase
the reaction rate. The deformability of the substrate on which a reaction
occurs is not known to affect this rate. In contrast, by carrying out reduction
of Gold and Silver salt on soft, crosslinked layers of poly(dimethylsiloxane)
(PDMS), we show here that surface tension driven deformation of the solid too
can increase the reaction rate. The PDMS contains SiH groups as organosilanes
which reduces the salt thereby producing the corresponding metallic
nano-particles. When an aqueous solution of the salt is dispensed as a sessile
drop on a sufficiently soft PDMS layer, nano-particles get generated at ~3
times the rate over which when the salt solution is dispensed as a pool on the
same surface. Unlike the pool, the drop has a three-phase contact line, where
it pulls up the solid forming a ridge. By balancing the resultant surface
stresses at the vicinity of this ridge, we have estimated the excess surface
free energy associated with it. We show that this excess energy can diminish
the activation energy barrier and increase the reaction rate to the extent that
would have been achieved by increasing the reaction temperature by over 30o C.
