Achieving large-scale polyelectrolyte membrane production by optimized multi-nozzle electrospray-assisted layer-by-layer printing

Abstract

Multi-nozzle electrospray-assisted printing offers a promising approach for high-throughput and large-scale production of advantageous emerging membranes such as polyelectrolyte multilayer (PEM) nanofiltration membranes. However, such demonstrations have been scarce, and the critical parameters affecting printing uniformity and membrane performance remain elusive. In this study, we developed a 10-nozzle electrospray system for large-area PEM membrane production through layer-by-layer printing with polyethyleneimine (PEI) and poly(sodium 4-styrene sulfonate) (PSS). We thoroughly evaluated the key parameters of electrospray droplets including size, flight and evaporation time. Additionally, we revealed that misalignment of nozzles and irregular Taylor cones deflected electrospray droplets, leading to their positional shift and ultimate uneven printing. The nozzles' reciprocating motion covering twice the nozzle spacing improved printing uniformity, with 93 % of the area showing a deviation within ±20 % of the average. Our system achieved an areal deposition mass of 0.78 g (PEI + PSS)/m2 and an impressive deposition efficiency of 95 %, attributed to controlled droplet trajectories. In addition, we discovered that total printing duration within 1 h was critical to prevent substrate drying and preserve membrane water permeability. Finally, we successfully produced a large-area PEI/PSS membrane measuring 40 × 60 cm2 in 1 h. The membrane exhibited a water permeability of 9.8 ± 1.3 L∙m−2∙h−1∙bar−1 and a PEG (1000 Da) rejection of 47 % ± 7 %, with performance deviations below 15 % across the membrane. This study demonstrates the feasibility of multi-nozzle electrospray-assisted printing for large-scale membrane production and provides valuable insights for optimizing operational parameters to enhance printing uniformity and membrane performance.