A micro-extrusion printhead assembly utilized in a micro-extrusion system to form parallel extruded gridlines of material on a substrate includes a nozzle having a tapered (e.g., triangular or trapezoidal) cross-section arranged such that a lower surface of each gridline is substantially wider than its upper edge, and such that side surfaces of the extruded gridlines reflect incident light beams into exposed surface areas of the substrate, thereby minimizing the effective shadowed surface area under the gridline. In one embodiment, the fluidic channels of each nozzle are fabricated by cutting or etching progressively wider channels into a series of rigid layers, and then stacking the rigid layers to form a layered nozzle structure. In another embodiment, a single layer is processed to include a tapered cross-section having the desired triangular or trapezoidal cross-section.