  Small (sub)-micron dust is present over the entire lifetime of protoplanetary
disks. As aggregation readily depletes small particles, one explanation might
be that dust is continuously generated by larger bodies in the midplane and
transported to the surface of the disks. In general, in a first step of this
scenario, the larger bodies have to be destroyed again and different mechanisms
exist with the potential to accomplish this. Possible destructive mechanisms
are fragmentation in collisions, erosion by gas drag or light induced erosion.
In laboratory experiments we find that the latter, light induced erosion by
Knudsen compression and photophoresis, can provide small particles. It might be
a preferred candidate as the dust is released into a low particle density
region. The working principle of this mechanism prevents or decreases the
likelihood for instant re-accretion or re-growth of large dense aggregates.
Provided that there is a particle lift, e.g. turbulence, these particles might
readily reach the surface of the disk.
