A method and apparatus for fabricating an array of biopolymers on a substrate using a biopolymer or biomonomer fluid, and using a fluid dispensing head. The head has at least one jet which can dispense droplets onto a substrate, the jet including a chamber with an orifice, and including an ejector which, when activated, causes a droplet to be ejected from the orifice. The method includes positioning the head with the orifice facing the substrate. Multiple droplets of the biopolymer or biomonomer fluid are dispensed from the head orifice so as to form an array of droplets on the substrate. A gas flow is directed through a venturi which has a throat opening communicating with the dispensing head chamber. A venturi control valve which particularly communicate with an outlet of the venturi, is adjusted to alter the chamber pressure. The venturi may be driven by a source of inert anhydrous compressed gas which assists in maintaining fluid in the head isolated from moisture.