A direct-reading device for measurement of patch-clamp micropipette tip diameters

This paper describes an electronic device for the measurement of the diameter of the tip opening of micropipettes. The device measures the threshold pressure required to produce bubbles from the micropipette submerged in a liquid and displays the tip inner diameter in micrometres. We demonstrate that this technique can be used effectively in a range of liquids of different density, surface tension and viscosity and that the thickness of the glass from which the micropipettes are made does not influence the measurements.