Vape devices containing highly viscous liquids can be problematic in delivering a consistent aerosol over the lifetime of a vape experiment due to liquid mobility, with the user potentially being unaware of reduced deliveries. To mitigate this problem a methodology was developed that visualised potentially changing aerosol delivery rates on a puff-by-puff basis.

A bluetooth in-line pressure drop (PD) transducer recording both the PD and visually showing the puff profile in ‘real’ time was developed to allow the user to observe the puff profile shape/PD change on a puff-by-puff basis. This technique can alert the user to increased PD, indicating volatilisation is dropping during puffing due to e-liquid fluidity (viscosity) restricting transport to the heater.

Multiple vape devices (nominally termed low, medium and high viscosity liquid depending on contents) were puffed on a vaping machine using the 55/3/30/square regime, on a puff-by-puff basis using various puffs blocks up to the lifetime of each vape device. The PD during puffing and block deliveries were measured.

Changes in delivery were evidenced in some of the vapes by device PD changing from 120 mmWg to 375 mmWG over a short period of time (< 10 puffs) whilst others showed no change in PD. Where high viscosity liquids were used with change to high PD, there was an 88 % drop in volatilisation over a 120 puff series of puff blocks as measured by mass recovered.

To mitigate the low aerosol collected mass (ACM) delivery rates the addition of a heater jacket to encase the vape pen devices, maintained at a steady temperature of 50 °C, showed the vape liquid can be kept sufficiently fluid to produce a constant PD and a steady stream of aerosol (0.76 mg/puff SD 0.0121, high viscosity device: 1.325 mg/puff SD 0.0258 medium viscosity device: 200 puffs), without producing potential thermal degradation products.