“…Fabrication techniques based on micromachined structures in silicon, which usually employ anodic bonding between Si and Borofloat glass substrates to make MEMS vapor cells [30], have shown great scalability and stability properties. Alternatively, photolithography of a photoresist, in combination with etching and glassblowing techniques, has been used to fabricate atomic microchannels [31] and, more recently, nanostructured alkali-metal vapor cells [32,33]. However, due to the planar bonding or lithographic strategy, all these cells do not show 3D versatility and have limited optical access.…”