Fig. 6: Schematic of the generated photoacoustic forces in a nanosheet on the substrate.
From: Photoacoustic 2D actuator via femtosecond pulsed laser action on van der Waals interfaces
a The case of asymmetric stress: the acoustic waves carry a resulting nonzero momentum (M) which is transferred to the substrate producing the unidirectional traction force (Ftraction) that drives the nanosheet to move with a velocity (vNS). b The case of symmetric stress: the resulting moment of two opposite acoustic wave and the traction forces are compensated.
