  The ALICE Inner Tracking System has been recently upgraded to a full silicon
detector consisting entirely of MAPS, arranged in seven concentric layers
around the LHC beam pipe. Further ahead, during the LHC Long Shutdown 3, the
ALICE collaboration is planning to replace the three innermost layers of this
new ITS with a novel vertex detector. The proposed design features wafer-scale,
ultra-thin, truly cylindrical MAPS. The new sensors will be thinned down to
20-40~{\textmu}m, featuring a material budget of less than
0.05\%~x/$\mathrm{X_{0}}$ per layer, unprecedented low, and will be arranged
concentrically around the beam pipe, as close as 18~mm from the interaction
point. Anticipating the first prototypes in the new 65~nm CMOS technology node,
an active R\&D programme is underway to test the response to bending of
existing 50~{\textmu}m thick ALPIDE sensors. A number of such chips were
successfully bent, even below the targeted innermost radius, without signs of
mechanical damage, while retaining their full electrical functionality in
laboratory tests. The curved detectors were subsequently tested during particle
beam campaigns, where their particle detection performance was assessed. In
this contribution, testbeam highlights from the data analysis of bent ALPIDE
sensors, will be presented. It was proved that the current ALPIDE produced in
the 180~nm CMOS technology retains its properties after bending. The results
show an inefficiency that is generally below $10^{-4}$, independent of the
inclination and position of the impinging beam with respect to the sensor
surface. This encouraging outcome proves that the use of curved MAPS is an
exciting possibility for future silicon detector designs, as not only the
sensor can survive the bending exercise mechanically, but the enticing
attributes that make it attractive for use in the inner tracking layers are
comparable to the flat state.
