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CORESTA Congress, Kunming, 2018, Smoke Science/Product Technology Groups, STPOST 42

Observation of wicking behavior of an electronic nicotine delivery system (ENDS) device using weight-time measurements

PLATT S.P.; THORN E.K.; RAGLAND R.B.; RUSYNIAK M.J.
Altria Client Services LLC, Richmond, VA, U.S.A.

The rate of liquid uptake (wicking) of an e-vapor liquid is an important factor for the performance of an electronic nicotine delivery system (ENDS) device. A common method for quantifying the wicking rate uses Lucas-Washburn theory. Here the time required for a liquid to travel a certain height in the material due to capillary action is determined. An alternative to this traditional height-time approach to measuring the wicking rate uses the mass uptake of the liquid by the material over time. Weight-time measurements consider the rate of liquid traveling throughout the entire wick whereas height-time measurements only consider a single observable edge. A modified Lucas-Washburn equation serves as a model equation for these weight-time measurements. This modified equation gives a capillary constant, an effective composite rate constant for the entire wicking process that includes both liquid parameters and wicking dimensions. The mass uptake of a variety of e-liquids by a wick made of fiberglass strands offers a test case to apply this method. A tensiometer serving as a hanging balance monitored the mass uptake of an e-liquid into an ENDS device wick over the time interval required for saturation. The calculated capillary constants from these experiments correlate with the liquid parameters of the modified Lucas-Washburn equation: viscosity, surface tension, and liquid density. The results show that weight-time measurements offer a direct and reproducible method to understand the wicking process observed in ENDS devices.