Grease the gears: how lubrication of syringe pumps impacts microfluidic flow precision

Pumps are indispensable for analytical applications and ensure controlled fluid movement. Syringe pumps are among today's most prevalent liquid delivery systems, especially for high-pressure, stable, low-flow-rate microfluidic applications. Due to moving mechanical parts of the assembly, regular maintenance is essential to ensure reliable operation and flow rates. However, lubrication of the mechanics is easily overlooked because the research focuses on novel analytical applications rather than on the maintenance of pumps. Here, we investigate the lubrication of the syringe pump guide rods with its effect on the flow rate stability after regular pump cleaning from contaminations. The guide rods of syringe pumps were thoroughly cleaned from any lubricant, and the flow rate for specified flowrates between 5 and 100 μL min-1 was measured, revealing tremendous flow rate fluctuations with a coefficient of variation (CV) value up to 0.34. In contrast, flow rate measurements of syringe pumps with lubricated guide rods show a five-fold smoother flow rate fluctuation depending on the specified flow rate with CV values below 0.07. These differences in flow rate's CV were most significant for pressure drops below 500 mbar, relevant for many lab-on-a-chip applications. In summary, we emphasize the awareness of lubricating moving parts of syringe pumps to achieve constant flow rates, minimize wear, and ensure the reliable operation of, for instance, accurate lab-on-a-chip workflows.