The electronic pressure regulator was controlled via a serial connection (RS-232) to the motion controller (A3200, Aerotech, Inc.). A glass slide (75 mm x 50 mm x 1 mm) was cleaned by rinsing with soap water, deionized water, and acetone. Then, a solution of 2 wt% PSS in milli-Q water was passed through a syringe filter (PALL Acrodisc 25 mm PTFE syringe filter 1 µm pore size), and spin-cast onto the freshly cleaned glass substrate (20 seconds at 500 RPM, 10 seconds at 150 RPM) and mounted on the motion stage beneath the printhead for use as a substrate. The substrate was aligned with the printhead axes to substrate tilt, and the toolpath and applied pressure were programmed controlled via manually written G-code.