This article presents nano-slit electrospray emitters fabricated by a micro- to nanofluidic via technology. The main advantage of the technology is the ability to position freely suspended nanochannels anywhere on a microfluidic chip, where leak-tight delivery of fluid from a fluid reservoir can be established through long microchannels. The technology has proven to be useful in creating electrospray emitters coupled to freely suspended microchannels. It was observed that filling of nanochannels through via connections with integrated microchannels occurs not only due to bulk capillary action. These observations lead to a redesign of the electrospray chips. Repeatable electrospray IV-curves could be obtained from fabricated nano-slit electrospray emitters. Moreover, integration of on-chip microfluidic components is one of the possibilities of the fluidic via technology presented.