Thermal radiation forces on planar structures with asymmetric optical response

Light carries momentum and, upon interaction with material structures, can exert forces on them. Here, we show that a planar structure with asymmetric optical response is spontaneously accelerated when placed in an environment at a different temperature. This phenomenon originates from the imbalance in the exchange rates of photons between both sides of the structure and the environment. Using a simple theoretical model, we calculate the force acting on the planar structure and its terminal velocity in vacuum, and analyze their dependence on the initial temperature and the geometrical properties of the system for different realistic materials. Our results unravel an alternative approach to manipulating objects in the nano and microscale that does not require an external source of radiation.