Modeling the photophoretic force on a perforated membrane

The photophoretic force exerted on an illuminated membrane vanishes when its size is much larger than the molecular mean-free-path. Perforations in the membrane can increase the force, but they make modeling the gas flow more difficult. In the present letter, a new model of gas interaction with a perforated surface is proposed. The direct simulation Monte Carlo method is used to calculate the flow-field and photophoretic force exerted on a perforated membrane, showing a significant increase in the force at high rarefaction parameters. This effect could be used to levitate membranes of a few centimeters in size at mesospheric altitudes.