Labs Idea #14: Improved Puff Sensing of E-Cigarettes
Some electronic cigarettes (e-cigarettes), tobacco heating products (THP) and heat-not-burn (HnB) devices use puff sensors to count the number of puffs or detect when a smoker starts to inhale. Some vapers or smokers prefer a lot of smoke. Others prefer less vaporized liquid or heated smoke. To enhance user experience of vaping or smoking a flow sensor could characterize volume, peak flow and duration of the inhalation in order to control the atomizer of liquids or heater of tobacco to suit user's preferences. Improving the vaping or smoking experience of e-cigarettes, THP or HnB devices to individual user needs could increase the switch rate from traditional cigarettes to modern vaping or smoking products and reduce the amount of harmful substances to which smokers and non-smokers are exposed.
Sensirion's miniaturized differential pressure sensor SDP3x is a semiconductor MEMS version of the traditional hot wire anemometer. The sensing principle is based on thermal conductivity of the gas flowing over the sensor surface (Figure 1).
Sensirion's differential pressure, respective flow sensor is easily integrated into an e-cigarette, tobacco heating product (THP) or heat-not-burn (HnB) device to accurately measure the inspiratory flow passing through the atomizer or heater before entering the smokers' lungs. Figure 2 depicts an integration example for a large e-cigarette. For smaller spaces in e-cigarettes, tobacco heating products (THP) or heat-not-burn (HnB) devices, Sensirion's CMOSens flow sensor die (with custom package) could be integrated directly into the flow path.
As opposed to diaphragm based differential pressure sensors, Sensirion's CMOSens differential pressure (aka flow) sensor characteristic shows high sensitivity especially at low differential pressures (Figure 3). This allows to reliably measure ultra-low differential pressures and therewith accurately measure the flow passing through the e-cigarette, tobacco heating product (THP) or heat-not-burn (HnB) device.
The measurement of an example inspiratory flow profile of two different smokers of e-cigarettes, tobacco heating products (THP) or heat-not-burn (HnB) devices is presented in Figure 4 & 5.
Inhalation duration, flow profile, volume (by integrating over the inhalation profile) as well as many other quantities such as the peak inhalation rate can easily be extracted from the curves shown in Figure 4 and 5.
The measurement results demonstrate that Sensirion's SDP3x differential pressure sensor is well suited to measure the inspired air flow in e-cigarettes, tobacco heating products (THP) or heat-not-burn (HnB) devices. The high sensitivity of the SDP3x allows highly accurate flow measurement across different type of vapers or smokers.
Specifically, the SDP3x integrated into e-cigarettes, tobacco heating products (THP) or heat-not-burn (HnB) devices allows to measure:
- puff detection
- duration and amplitude of inhalation
- inhalation flow characteristics
To integrate the small flow sensor (Figure 6) used inside of Sensirion's differential pressure sensor SDP3x series (Figure 7) into e-cigarettes, tobacco heating products (THP) or heat-not-burn (HnB) devices please contact Sensirion. For first feasability tests we propose to use the flow and differential pressure sensor evaluation kit EK-P4 (Figure 8).