Looking to do coaxial electrospinning of polystyrene and PEO. I need to order a coaxial needle but I have not used such a technique yet. The manufacturer offers several options of diameters (inner and outer diameters ) and length, I usually do PS electrospinning with 17G and 19G is also fine. PS solution would be as the core of the prospected fibres while the PEO will use as the shell or the second layer. any reply will be considered