TITLE: Measure Effects of Manufacturing Variations of ENDS on coil Lifetime and Aerosol Generation
AUTHORS: Qutaiba Saleh, Edward Hensel, Nathan C. Eddingsaas, Risa Robinson

[DESCRIPTION]
<div class = "text-blocks"><div class = "text-block">Manufacturing variations in coil resistance, initial pod mass, and e-liquid color could have effects on the performance of electronic nicotine delivery system (ENDS). Specifically, these variations could affect coil lifetime, total particular mater yield, and e-liquid consumption rate. This protocol is a step by step explanation of the test procedure used to assess these effects. The steps describe the preparation of test specimens, making measurements, and running puffing sessions on the device under test. While this protocol was used for Vuse ALTO ENDS, it was written in a way to make it as generic as possible so that it can be applied to other brands and types of ENDS. This protocol was successfully used in bigger research project. The article which this protocol is associated with will be added to the Metadata once it is published.</div></div>

[STEPS]
?. [Samples (pods) Preparation]
Select the pods to be included in this experiment and execute all steps in this section on each pod.
?. [Samples (pods) Preparation]
Document the UID for all pods.
?. [Samples (pods) Preparation]
Visually inspect the color of the e-liquid in the pods and classify the pods based on e-liquid color into Light or Dark. The pictures below gives examples of a pod with light e-liquid color and a pod with dark e-liquid color. If possible, the pods can be classified into more than two color groups.
?. [Samples (pods) Preparation]
Visually inspect the pod for any damage due to shipping, storage, or any other reason. Exclude any pods with damages.
?. [Samples (pods) Preparation]
Take a picture of the pod to document its color and undamaged status.
?. [Before Conducting Puffing Session]
Make sure the ENDS PCU is fully charged. If not, wait until it is fully charged before proceeding to the next step. This step is to eliminate the effects of variable battery level on ENDS performance. In this experiment, the ALTO ENDS was continuously connected to the charger while the ENDS was being used, as allowed by the manufacturer.
The ENDS devices uses lithium batteries. It is important to use caution when working on the battery even if the battery is discharged.
?. [Before Conducting Puffing Session]
Take “Before” reading for coil resistance using coil resistance testing apparatus. A protocol to build coil resistance testing apparatus for Vuse ALTO can be found using the link below.
?. [Before Conducting Puffing Session]
Install the filter pad in the filter pad holder.
?. [Before Conducting Puffing Session]
Install the ENDS pod in the ENDS PCU.
?. [Before Conducting Puffing Session]
Connect the ENDS assembly to the emission system (PES-1 in this case). Use short connecting tube to connect the mouthpiece of the pod to the inlet of the filter holder. Use laboratory wrapping film to fix the tube to the mouthpiece.
?. [Run Puffing Session]
Run trial based on the predefined puffing profile. The puffing profile used in this experiment consists of uniform square puffs with 18.33 mL/Sec flowrate, 5.5 Sec  puff duration, and 11 Sec puff interval. Based on the amount of e-liquid remaining in the pod, the number of puffs per session is selected to be 20, 10, or 5 puffs. This is to increase the precision at which coil lifetime is measured.
?. [After Puffing Session]
Remove the ENDS pod from the ENDS PCU and take “After” trial coil resistance measurement using the coil resistance test apparatus. This measurement should take place as soon as the session ends, this reading tries to assess coil resistance while it may still be warm due to usage.
?. [Before Conducting Puffing Session]
Take "Before" pod (the e-liquid reservoir and coil) mass and filter pad mass using gravimeter.
?. [After Puffing Session]
Remove the filter pad from the filter pad holder within  of the conclusion of the trial and take "After" reading for filter pad mass.
?. [After Puffing Session]
Remove the ENDS assembly from the emission system within  of the conclusion of the trial.
?. [After Puffing Session]
Take “After” reading for pod (the e-liquid reservoir and coil) mass measurement using gravimeter.
?. [After Puffing Session]
Assess coil resistance of the pod.
If it is in the range of ~ 0.7 - 2 Ω,  coil was not damaged (functional). If it is increased to order of 400 kΩ,  coil was damaged (failed). These coil resistance ranges are for Vuse ALTO pods. Use appropriate values for other products.
?. [After Puffing Session]
Assess the amount of e-liquid left in the pod to determine the number of puffs to be used in the next session trial. Profiles of 20, 10, 5 are used. As the amount of e-liquid in the pod was consumed, profiles with a smaller number of puffs are used. This was to increase the precision at which coil lifetime was measured.  to conduct the next puffing session.
?. [After Puffing Session]
Document any other information relevant to the research question being investigated. It is always important to take notes of facts such as (droplets condensed on the connecting tube between pod and filter pad holder). Such notes could be critical in explaining anomalies and understanding the final result.
?. [After Puffing Session]
Record of the number of puffs the pod worked until coil failure.
In our experiment for Vuse ALTO, coil lifetime of 15 pods ranged from 135 to 215 puffs.
?. [After Puffing Session]
Archive the pod in accordance with the laboratory’s data management plan and   to start working on the next pod assigned for this experiment.
?. [Before Conducting Puffing Session]
Connect the filter pad holder to its appropriate place in the emission system (PES-1 in this case).
?. [Result Analysis]
Some of the important data points produced in this experiment can be organized in a table to simplified the later analysis as follows. The statistical mean and standard deviation can be also added to this table as applicable. Pod IDInitial Coil Resistance Initial E-liquid ColorInitital Pod MassEnd Pod MassE-liquid Net Mass (Col. C - Col.D)Coil LifetimeTotal Particulate Mater (TPM) per puff of First SessionPod 1Pod 2.................Pod nMean STD
Pod IDInitial Coil Resistance Initial E-liquid ColorInitital Pod MassEnd Pod MassE-liquid Net Mass (Col. C - Col.D)Coil LifetimeTotal Particulate Mater (TPM) per puff of First SessionPod 1Pod 2.................Pod nMean STD
?. [Result Analysis]
In addition to the statistical mean and standard deviation which are already mentionedThe data in the table from the previous step can be analyzed test relations between the desired variables this experiment focuses on. Next is a list some of the suggested correlation test:The correlation between initial coil resistance and coil lifetime.The correlation between initial coil resistance and initial TPM.The correlation between initial pod mass (or e-liquid net mass) and coil lifetime.The correlation between initial pod mass (or e-liquid net mass) and initial TPM.The MATLAB functions fitllim and corrcoef can be used make these testsT-tests can be conducted to test the effects of e-liquid color:T-test between coil lifetime of the pod with light e-liquid and dark e-liquid.T-test between TPM of the pod with light e-liquid and dark e-liquid.The MATLAB functions fitllim and corrcoef can be used make these testsT-tests can be conducted to test the effects of e-liquid color:T-test between coil lifetime of the pod with light e-liquid and dark e-liquid.T-test between TPM of the pod with light e-liquid and dark e-liquid.The MATLAB function ttest can be used.
?. [Result Analysis]
Further analysis can be conducted for more understanding of the data. Plots can be used to show the correlation of the experiment variables at the session level to explain their behavior. Some the the suggested plots are:Plot the coil resistance against the TPM at each session.Plot the coil resistance against pod mass at each session.Plot the pod mass against TPM at each session.
The results of the experiment conducted using this protocol is presented in our article "Effects of Manufacturing Variation in Electronic Cigarette Coil Resistance and Initial Pod Mass on Coil Lifetime and Aerosol Generation". A link to the paper is presented in the Metatdata section of this protocol.