The present invention provides for a structure comprising a plurality of emitters, wherein a first nozzle of a first emitter and a second nozzle of a second emitter emit in two directions that are not or essentially not in the same direction; wherein the walls of the nozzles and the emitters form a monolithic whole. The present invention also provides for a structure comprising an emitter with a sharpened end from which the emitter emits; wherein the emitters forms a monolithic whole. The present invention also provides for a fully integrated separation of proteins and small molecules on a silicon chip before the electrospray mass spectrometry analysis.
STATEMENT OF GOVERNMENTAL SUPPORT
 The invention was made with government support under Contract Nos. DE-AC02-05CH11231 awarded by the U.S. Department of Energy and Grant R21GM077870 awarded by the National Institutes of Health. The government has certain rights in the invention.