Upgrade of the LHCb VELO detector

The LHCb experiment is a single-arm forward spectrometer optimised for performing heavy-flavour physics analyses, using proton-proton collisions provided by the LHC machine. A major upgrade of the LHCb experiment will take place prior to the start of Run 3 operations in 2021. The upgraded Vertex Locator (VELO) is an essential component of this upgrade. Its main role is to enable high precision track and vertex reconstruction, with data-driven readout to the software trigger at 40 MHz, in the higher-luminosity environment of Run 3. To achieve this goal, significant improvements are planned with respect to the current detector, including a switch from microstrips to pixels, upgraded electronics, and a new cooling system. I will briefly motiviate the need for an upgrade, describe the main aspects of the VELO upgrade design, and show highlights of recent sensor characterisation studies using the CERN SPS test beam.