Abstract
A streaming potential appears in the tip of a glass micropipette when a hydrostatic pressure is applied between the inside and outside electrolyte of the tip. In this experiment, an attempt is made to apply the streaming potential to hydrostatic pressure measurements in limited volume biological compartments.
This paper deals with an experimental analysis of the streaming potential in a glass micropipette filled with NaCl solution. And on the basis of this analysis, some principles are described which contribute to the design of the new biological extrafine pressure transducer. The theoretical equation for the streaming potential Esp is given by the Helmholtz-Smoluchowski equation as follows :
Esp= (εζ/4πση) P=Sp·P
where P is the pressure difference, ε is the dielectric constant, η is the viscosity, σ is the conductivity of the solution, and ζ is the “zeta-potential”. The equation indicates that, when pressure is applied to the micropipette which is filled with an electrolyte, a streaming potential appears at the tip in proportion to the applied pressure.
It has experimentally been found that the pressure sensitivity Sp is independent of the tip, size, but depends on the concentration C, pH and temperature of the solution. Sp is in proportion to C-1.2, and, for 0.9% NaCl solution, Sp is about 2 μV/mmHg and its variation for pH and temperature is about +5%/pH unit and +1%/deg, respectively.
As a result of an exploratory biological experiment, a waveform of blood pressure in the iliac artery of a toad is demonstrated.
