Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Method for Measuring the Volume of Nominally 100 um Diameter Spherical Water-in-Oil Emulsion Droplets



John A. Dagata, Natalia Farkas, John A. Kramar


This report describes an equivalent volume measurement method using optical microscopy for estimating the mean volume of nominally 100 um diameter spherical droplets. The droplets are the aqueous phase of proprietary water in oil emulsions used in a commercial droplet digital polymerase chain reaction DNA quantitation system. This method is based on the transition of spherical droplets to polygonal structures at constant volume. Close packed spherical emulsion droplets confined within a microfluidic channel transform into a space filling polygonal lattice as the oil phase evaporates. The microfluidic channel height determines the resulting lattice dimensions such that the mean droplet volume is traceable to the unit of length through a determination of channel height.
Special Publication (NIST SP) - 260-184
Report Number


Droplet digital polymerase chain reaction (ddPCR) Droplet volume Optical microscopy Plateau border channels Princen’s model Water-in-oil emulsions


Dagata, J. , Farkas, N. and Kramar, J. (2016), Method for Measuring the Volume of Nominally 100 um Diameter Spherical Water-in-Oil Emulsion Droplets, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created July 13, 2016, Updated November 10, 2018