AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment in progress at CERN has planned to produce antihydrogen ( ) by using the resonant charge exchange process between orthopositronium (o-Ps) and antiproton ( ). Its primary goal is the realization of a cold beam for the first measurement of the Earth's gravitational acceleration on antimatter. A demanding condition for large o-Ps - cross section is the cooling of o-Ps at temperatures lower than at least 160 K. We will present recent results of o-Ps formation and cooling at cryogenic temperatures in a novel silicon positron/Ps converter in which oxidized nano-channels perpendicular to the surface were produced. The possibility to tune the nano-channels dimension to optimize o-Ps kinetic energy emission and to avoid o-Ps quantum confinement is discussed.