How does an electronic cigarette work? That’s a question that lots of people don’t seem to have a good answer to – and many of them, including scientists and journalists, really should know better. Luckily it’s not all that difficult to explain.
Electronic cigarettes are also called vapes, and that gives a big clue to how they work. The big white cloud they create isn’t smoke; it’s an aerosol made up of vapour and tiny droplets of liquid. All the electronics and other components inside an e-cig are there to create this aerosol out of the liquid in the tank.
Every e-cigarette has three main components: The battery, the tank and the atomiser. All of these come in a huge variety of types and sizes, and quite often you’ll see two or even all three combined into a single unit. However the device is put together, though, it will definitely have all three – otherwise it wouldn’t work. Here’s what they do.
The battery
An e-cigarette’s battery provides the electricity that powers the whole thing. Almost all e-cigs use lithium ion or lithium polymer batteries, because these can pack a lot of energy into a small space; vapes drain a lot more current than most portable electronics, so they need good batteries.
All smaller vapes – the ones that look like traditional cigarettes, plus the more popular pen-style models – have a built-in battery. This means that when the battery wears out (usually after about 300 charge cycles) you have to throw the whole device away and replace it.
Some larger e-cigs – the devices called “mods” – also have built-in batteries. These batteries tend to be bigger and store a lot more power, so they’ll usually outlive the rest of the device. By the time the battery has been through enough cycles that it won’t hold a decent charge anymore, something else – usually one of the buttons – has worn out.
Finally, most mods use removable batteries. These come in several sizes but almost all modern devices use the 18650 size. Removable batteries have several advantages. The obvious one is that if the batteries go flat, you can just change them and keep using the mod. This lets you quickly recharge the flat ones in a standalone charger.
The tank
All e-cigarettes have some sort of tank to store the liquid and feed it to the wick. In cigalike models this can be a small, disposable plastic cartridge; others have a refillable tank. Until May 2017 these came in a wide range of capacities, but thanks to a controversial EU law they’re now limited to 2ml.
E-liquid tanks are actually quite complicated. The big problem for the designer is to make a tank that will let air in, without letting liquid leak out. The simplest way is to have the coil above the tank with the wicks hanging down into the liquid. This is often seen in small “clearomiser” tanks used on pen-style devices, but some larger ones use it too.
Other tanks have the coil at the bottom of the tank, surrounded by a chimney leading to the mouthpiece. The wick leads out through small holes in the chimney, and the air holes are in the base of the tank. As long as there’s enough liquid in the tank to cover the wick holes, a partial vacuum inside prevents any escaping through the airholes.
The atomiser
The vapour is actually produced by a coil of wire or metal strip, wrapped round a wick. Modern wicks are usually made of cotton, but in the past silica, ceramic and even steel mesh have been used. In many ways this the simplest part of the device; the wick carries liquid to the coil which, heated by the battery, vaporises it.
Some atomisers are “rebuildable” – you have to make your own coil and wick. Others use disposable units which are simply unscrewed and replaced every week or two.
So how does it all work?
A fully set up e-cigarette has a charged battery, a tank full of juice and a coil. When you press the button (or take a puff, with the cheapest models) the battery starts feeding power to the coil. Because this is made of thin metal it quickly heats up, and so does the liquid in contact with it. Almost instantly, the coil is surrounded with a small, but dense, cloud of vapour.
When the vaper takes a puff air is drawn in through the air holes and over the coil. This pulls the vapour up to the mouthpiece, allowing more liquid to evaporate. The coil will carry on creating vapour until the airflow stops or it overtakes the wick’s ability to feed it liquid. Most vapers inhale for up to five or six seconds, and with a modern e-cig that can create a lot of vapour.