the invention relates to an electrospray ionization device for forming a stream of ionized sample molecules . the device comprises a sample introduction zone for receiving a liquid - form sample , a tip for spraying the sample into aerosol or gaseous form , and a flow channel connecting the sample introduction zone and the tip . according to the invention , the flow channel comprises an array of transversely oriented microstructures adapted to passively transport the liquid - form sample introduced to the sample introduction zone to the tip by means of capillary forces . the invention concerns also a manufacturing method and applications of the esi device , in particular mass spectrometry . the device can be used without external pumping of sample liquid .