  We report a self-guided and "stimulated" single-crystal growth acceleration
effect in static super-saturated aqueous solutions, producing inorganic
(KH$_2$PO$_4$) and organic (tetraphenyl-phosphonium-family) nonlinear optical
single-crystals with novel morphologies. The extraordinarily fast
unidirectional growth in the presence of complete lateral growth suppression
defies all current impurity, defect and dislocation based crystal growth
inhibition mechanisms. We propose a self-channeling-stimulated accelerated
growth theory that can satisfactorily explain all experimental results. Using
molecular dynamics analysis and a modified two-component crystal growth model
that includes microscopic surface molecular selectivity we show the lateral
growth arrest is the combined result of the self-channeling and a
self-shielding effect. These single-crystals exhibit remarkable mechanical
flexibility in winding and twisting, demonstrating their unique advantages for
chip-size quantum and biomedical applications, as well as for production of
high-yield/high-potency pharmaceutical materials.
