Atmospheric Pressure Difference Centrifuge for Stable and Consistent Plasma Separation

Abstract

Separating plasma from micro-scale whole blood is a necessary step for point-of-care hematology diagnosis and therapy. Current manual centrifuges offer an affordable, simple, and electricity-free method for plasma separation with low sample requirement. However, variations in manual operations and user errors often lead to inconsistent separation efficiency and unreliable results. Inspired by the constant atmospheric pressure, we develop an electricity-free centrifuge (henceforth called ‘Atmosfuge’) with consistent separation efficiency and minimal separation variations. The Atmosfuge comprised a sealed syringe and a gear transmission system. During plasma separation, the syringe rod was first pulled to create a vaccum in the barrel. Upon releasing, constant atmospheric pressure difference between internal air pressure of the barrel and the external atmospheric pressure would push the rod and drove the gear, rotating the blood sample for plasma separation. It ensures a uniform rotating speed (~2300 rpm) across different users. By harnessing the Boycott effect and adjusting the centrifugal radius, we can achieve a plasma yield of ~93% and purity of ~99.99% in separating 15 μL whole blood within 250 s. In addition, we integrated the Atmosfuge with a calibration ruler for visible and accurate hematocrit measurement. Finally, the separated plasma were tested for blood glucose detection by integrating microfluidic cloth-based analytical devices (μCADs) and colorimetric assays. Given its consistent separation efficiency and simple operation, Atmosfuge present a cost-effective alternative to traditional centrifuges, particularly in medical resource-limited regions.