  The Planet Formation Imager (PFI) is a near- and mid-infrared interferometer
project with the driving science goal of imaging directly the key stages of
planet formation, including the young proto-planets themselves. Here, we will
present an update on the work of the Science Working Group (SWG), including new
simulations of dust structures during the assembly phase of planet formation
and quantitative detection efficiencies for accreting and non-accreting young
exoplanets as a function of mass and age. We use these results to motivate two
reference PFI designs consisting of a) twelve 3m telescopes with a maximum
baseline of 1.2km focused on young exoplanet imaging and b) twelve 8m
telescopes optimized for a wider range of young exoplanets and protoplanetary
disk imaging out to the 150K H2O ice line. Armed with 4x8m telescopes, the
ESO/VLTI can already detect young exoplanets in principle and projects such as
MATISSE, Hi-5 and Heimdallr are important PFI pathfinders to make this
possible. We also discuss the state of technology development needed to make
PFI more affordable, including progress towards new designs for inexpensive,
small field-of-view, large aperture telescopes and prospects for Cubesat-based
space interferometry.
