  Within a unified formulation, encompassing self-electrophoresis,
self-diffusiophoresis, and self-thermophoresis, we provide a simple integral
kernel transforming the relevant surface flux to particle velocity for any
spheroid with axisymmetric surface activity and uniform phoretic mobility. We
define efficacy, a dimensionless efficiency-like quantity expressing the speed
resulting from unit absolute flux density on the surface, which allows a
meaningful comparison of the performance of different motor designs. For
bipartite designs with piecewise uniform flux over complementary surface
regions, the efficacy is mapped out over the entire range of geometry (discotic
through sphere to rod-like) and of bipartitioning, and intermediate aspect
ratios that maximize efficacy are identified. Comparison is made to
experimental data from the literature.
