The real name of an “electronic cigarette” is a steam device and this gives us a good indication of how they work. The large white cloud they create is not smoke, it is an aerosol of vapor and tiny droplets of liquid. All the electronic and other components of a e-cig are designed to generate this aerosol from the liquid (the e-liquid) in the tank.  Each vapor has three main components: the battery, the tank and the evaporator. All are available in a wide variety of types and sizes, and usually two or even all three are combined into one unit.

Power supply or battery

The battery of an electronic cigarette provides the power that runs the entire system. Almost all devices use lithium-ion or lithium-polymer batteries because they can store a lot of energy in a small space. Steam consumes much more energy than most portable devices and therefore requires good batteries. All small e-cigs, especially those that look like traditional cigarettes and many of the most popular pen models on the market today, have a built-in battery. This means that when the battery is depleted (usually after about 300 charge cycles), the entire device must be discarded and replaced. Some of the larger devices, which are called “mods” in steam language, also have batteries permanently installed on board. However, these batteries are usually larger and store much more energy, so they usually last longer than the rest of the device. If the battery has been cycled enough times that it can no longer maintain a proper charge, another component, usually one of the buttons, is usually already worn out. Most mods available today, however, use replaceable batteries. They are available in different sizes, but almost all modern devices use size 18650 (18 mm diameter for 65 mm length and the “0” in the specification is a gift). Replaceable batteries have several advantages. It is obvious that if the batteries are empty, you can simply replace them and continue to use the mod. And empty batteries can then be quickly recharged in a separate charger for reuse.

The liquid storage tank

All e-cigs have a type of tank to store the liquid and feed it to the wick. In some models it may be a small disposable plastic cartridge, others have a refillable tank. They used to be available in different capacities, but thanks to a controversial law, they are now limited to 2 ml almost everywhere in the EU. The big problem for the designer is to build a reservoir that lets air in without letting the liquid out. The easiest way is to mount the coil (also called spool) above the tank with the wicks hanging in the liquid. This is often seen in the small “clearomizer” tanks used on pencil appliances, but some larger tanks also use this principle. Other tanks have the coil at the bottom of the tank surrounded by a chimney leading to the tip. The wick passes through small holes in the base of the evaporator and air holes are also usually built into the base of the tank. As long as there is enough liquid in the tank to cover the wick holes, a partial vacuum inside prevents liquid from flowing through the air holes into the actually dry evaporation chamber. The e-liquid is mainly composed of propylene glycol.

The evaporator

Vapor is actually generated by a coil (winding, spool) of wire or metal strip wound around a wick. Modern wicks are usually made of cotton, but in the past, silica, ceramics and even steel fabrics were used to transport liquids. In many ways, this is the simplest part of the device. The wick transports the liquid from the tank to the coil, which is heated by the current from the battery. Some vaporizers can be mounted . These devices require the user to make and install their own bobbin using wire and roving material. Others use disposable vaporizer units, which are simply screwed on and replaced every few weeks. When you press the button (or make a gesture on the cheaper models), the battery current starts flowing through the spool. Because it is a thin metal, it heats up very quickly. The same applies to the liquid in contact with it through the wick. Almost immediately, the coil is surrounded by a small but dense cloud of vapor. When the steam vessel now catches a current of air, the air is sucked through the air holes and over the coil. This draws the steam produced towards the mouthpiece and allows more liquid to evaporate. This means that the coil continues to produce steam until the power supply is interrupted again or the wick’s ability to supply liquid to the coil is overloaded. The result of the latter is an “experiment” that each steam will experience at some point in its “career” and is called a “dry run”. In the end, nothing but the terrible taste of the burnt absorbent cotton. However, most vapers only inhale for five or six seconds, and at that time a modern e-cig can produce a considerable amount of delicious steam.