"Milky Way Black Holes and the Tech to Find Them"

The landscape for studies of stellar-mass black hole origins, evolution, and demographics has expanded dramatically not only with the detection of gravitational waves; but also the explosion of EM photometric and astrometric time domain surveys. Time domain microlensing surveys are particularly valuable for finding isolated black holes in our Milky Way. Microlensing probes black holes across the mass spectrum in a relatively unbiased manner. I will present observational results, including the first detection of a free-floating black hole, and population simulations that show how sensitive microlensing surveys are to the black hole mass function, binary fraction, and velocity distribution. I will also discuss the photometric and astrometric technologies needed to expand the sample of stellar mass black holes know in the Milky Way, including next-generation adaptive optics systems for precise astrometry, small space satellites for precise photometry over wide fields, and large space observatories, such as the Nancy Grace Roman Space Telescope, that simultaneously deliver photometry and astrometry for microlensing events. These technologies and observatories will likely expand the sample of known Milky Way black holes by 100x in the coming decade.