  A novel approach for designing the next generation of vertex detectors
foresees to employ wafer-scale sensors that can be bent to truly cylindrical
geometries after thinning them to thicknesses of 20-40$\mu$m. To solidify this
concept, the feasibility of operating bent MAPS was demonstrated using
1.5$\times$3cm ALPIDE chips. Already with their thickness of 50$\mu$m, they can
be successfully bent to radii of about 2cm without any signs of mechanical or
electrical damage. During a subsequent characterisation using a 5.4GeV electron
beam, it was further confirmed that they preserve their full electrical
functionality as well as particle detection performance.
  In this article, the bending procedure and the setup used for
characterisation are detailed. Furthermore, the analysis of the beam test,
including the measurement of the detection efficiency as a function of beam
position and local inclination angle, is discussed. The results show that the
sensors maintain their excellent performance after bending to radii of 2cm,
with detection efficiencies above 99.9% at typical operating conditions, paving
the way towards a new class of detectors with unprecedented low material budget
and ideal geometrical properties.
