Alcohol exposure has been postulated to adversely affect the physiology and function of the red blood cells (RBCs). The global pervasiveness of alcohol abuse, causing health issues and social problems, makes it imperative to resolve the physiological effects of alcohol on RBC physiology. Alcohol consumed recreationally or otherwise almost immediately alters cell physiology in ways that is subtle and still unresolved. In this paper, we introduce a high-resolution device for quantitative electrofluidic measurement of changes in RBC volume upon alcohol exposure. We present an exhaustive calibration of our device using model cells to measure and resolve volume changes down to 0.6 fL. We find an RBC shrinkage of 5.3% at 0.125% ethanol (the legal limit in the United States) and a shrinkage of 18.5% at 0.5% ethanol (the lethal limit) exposure. Further, we also measure the time dependence of cell volume shrinkage (upon alcohol exposure) and then recovery (upon alcohol removal) to quantify shrinkage and recovery of RBC volumes. This work presents the first direct quantification of temporal and concentration-dependent changes in red blood cell volume upon ethanol exposure. Our device presents a universally applicable highresolution and high-throughput platform to measure changes in cell physiology under native and diseased conditions. KEYWORDS: size of red blood cells, alcohol-induced shrinkage of biological cells, resistive pulse technique, micropores, electrofluidic devices ■ SIGNIFICANCE STATEMENTThe physiological changes in red blood cells caused by alcohol are not well understood, specifically the changes in cell volume that directly affect the oxygen carrying function of RBCs. Most of these changes are subtle and difficult to quantify. In the last decade, multiple methods have been used to measure this subtle change in cell size caused by alcohol exposure. The focus of this work is an electrofluidic sensing approach that accurately measures changes in cell volume of a cell population at single-cell resolution. The approach has potential to rapidly provide changes in cell volumes in cases like chemical exposure, malaria infection, large population sickle-cell disease screening, and quantifying cell lysis in a label-free, low-cost, and microscopy-independent way.