Introduction

The standard e-cigarette involves an electric heating coil that vaporises a liquid solution consisting of propylene glycol and/or vegetable glycerin, flavourants and, frequently, nicotine. Typically, the liquid is delivered to the heating coil via saturated wicking material. However, ‘dripping’ is another method that involves the application of liquid to the coil of a direct drip atomiser or rebuildable dripping atomiser.1 2 Users report that dripping provides greater vapour yields, stronger throat hit and a better flavour.3

Dripping is not without drawbacks. Notably, the higher temperatures involved may increase toxicant yield, although an update examining more contemporary designs may be needed.1 4 Additionally, dripping is time consuming. It requires transferring liquid from a separate container to the coil.1 This process must be repeated every few puffs to avoid ‘dry puffs’, as the liquid is vaporised and the heating coil dries out. Dry puffs yield more toxicants and may be accompanied by an aversive taste.1 5 Avoiding dry puffs by adding more liquid is challenging, as too much liquid ‘floods’ the coil, preventing vapour production. Furthermore, monitoring the amount of liquid consumed sometimes was challenging.