Bio-plasma physics: Measuring Ion Transport Across Cell membranes with Plasmas

A recent theoretical publication in the American Journal of Physics [1] investigates a mathematical model of plasma double layers, and their applicability to understanding ion transport across cell membranes. Cell membranes have selective permeability to the transport of different charged particles, similar to ion and electron movement across a double layer in a plasma. An existing voltage difference between the cells internal cytoplasm and the external bio-plasma causes a double layer to form between the cytoplasm and the bio-plasma. We present our design of a plasma created in a vessel with two distinct cross sections, similar to the model mentioned in the paper. When two plasmas of different cross sectional areas are considered, a double layer in the plasma forms on the interface between the two separate volumes. We use a Langmuir probe to evaluate plasma parameters such as electric potential, electric field, and charge density in the areas inside and surrounding the plasma double layer. These are used to show the similarity between charge transport across a plasma double layer, and ion transport across a cell membrane. [1] M. Uehara, K. K. Sakane, H.S. Maciel and W.I. Urruchi, "Physics and Biology: Bio-plasma physics," Am. J. Phys. 68 (5), 450-455 (2000).