The invention provides related apparatus and methods of making an integrated electrospray tip by depositing ionic and/or electronic conductor materials onto a planar substrate. The invention also features methods of forming an electrospray apparatus comprising coupling a first planar substrate to the surface of a second planar substrate, wherein a surface on at least one of the substrates includes one or more microfluidic channels and/or reservoirs which are at least partially or totally enclosed therebetween. The conductive regions of the apparatus do not intersect the microfluidic channels within other portions of the apparatus provided preferably. The invention further provides related apparatus and methods for manufacturing and using microfluidic devices with integrated electrodes for electrospray ionization. The electrospray apparatus in some embodiments may include an electronic conductor electrode or an ionic conductor electrode formed from a microfluidic channel containing a conductive material selected from a variety of solutions and gels.