A turbine can convert translational kinetic energy of convective flows into rotation
and is one of the most important machines to harvest energy from nature. Here, we
propose a theoretical prototype of a micro-turbine that is powered purely by an external
diffusive heat or mass flux. The turbine rotates perpendicular to the external thermal
or chemical gradient due to fore-and-aft asymmetric thermophoresis or diffusiophoresis.
Thus, its performance does not need alignment. The prototype turbine is validated
by means of computer simulations. The results show that the angular velocity of the
turbine sensitively depends on its structure and interactions with the solvent. This
perpendicular-axis phoretic turbine provides large flexibility and the possibility
to exploit existing thermal or chemical energies at small scales.