The Large Hadron Collider is due to be switched on at CERN this Friday, and I hope and trust that in the course of its operation it will generate a profusion of mini black holes. Mini black holes normally evaporate very quickly, and sadly pose no threat of destroying the world.
Mini black holes could, however, be put to hugely beneficial technological use. Black holes can, of course, be electrically charged, hence if one could create an electrically charged mini black hole, and if one could prevent the mini black hole from evaporating, then one could use electric fields to move and position the mini black holes.
How does one prevent them from evaporating? Well, the smaller a black hole, the greater the temperature of its event horizon, but a black hole will only evaporate if its temperature is greater than the temperature of its environment. Place a mini black hole in a heat bath at the same temperature, and it will be in thermodynamic equilibrium with the heat bath, and will not evaporate.
Now, a mini black hole like those that the LHC might produce, would have a temperature of about 1014 Kelvin, which is about 25 billion times hotter than the surface of the Sun. Hence, to move and manipulate mini black holes, and to build technological devices incorporating them, we would need to hold them with electromagnetic fields in a high-temperature heat bath. I leave this as an exercise to experimental physicists.
Once this problem has been solved, we will be able to construct a new generation of super-powerful Hoovers, each employing an array of mini black holes to suck up the dirt from the floors and carpets of our homes and workplaces. Obviously, as the black holes suck up the dirt, they will begin to grow in size, so they will need emptying occasionally. Rather as one removes the bag, once full, from a contemporary vacuum cleaner, one would simply remove the black hole module, lower the temperature of the heat bath slightly, and allow a quantity of mass-energy to evaporate in the form of a brisk gamma ray shower.