The measured dimensions were then implemented in our numerical model (Fig. ). As can be seen in figure (b), we were able to etch straight channel walls enabling us to produce nominally walls as thin as 13 µm with an etch depth of 192 µm. At the bottom of the channel, the silicon wall still had a width of 6 µm, which is thick enough to prevent the whole structure from collapsing during the acoustic excitation.