system
Given the following post, respond as if you're commenting on Reddit:
human
Is it possible to create a microscopic flame?

All flames, such as from a candle or lighter all tend to go out after reaching a minimum size. I suspect that simply making a tiny source isn't enough to do it. For example, birthday candles are much smaller than standard candles, but their flame is only marginally smaller.
Is there some limiting factor?
gpt
The answer is sort of. You can not create an extremely small flame from a source such as a traditional candle. But there is a way to create micro flames.  This is called microcombustion and they are flames smaller than the width of a millimeter.  They are typically made in small hard ceramic combustors (such as alumina oxide) and they burn at temperatures of up to 2000 C. The combustors have small channels through which the fuel flows and the flame burns. They are typically fueled by hydrocarbons and oxygen. Methane, butane, propane, etc.

The two inlet flows of the fuels meet and combine at some point and then you have your combustible gas. The point at which the two flows meet exhibits turbulent flow and this is the limiting factor at ignition for the combustor due to wall conditions and fluid dynamics not worth explaining here. Turbulent flow tends towards extinction for a flame. Typically a large candle type flame will be seen at the end of the exhaust channel.

As the combustor ramps up to its max temp (steady state) the walls of the exhaust channel heat up and begin to provide the thermal energy necessary for the gases within the channel to ignite. You will hear loud pops as ignition events begin to occur within the channel. As the temperature of the wall increases due to the heat seen from the exhaust flame, the ignition events begin occurring closer to the mixing points of the 2 fuels.

Finally at steady state the walls of the combustor at the mixing point of the fuels is so hot that the gases ignite immediately upon mixing. Due to the turbulent nature of the flow, they go out almost immediately.  They are also almost immediately replaced by fresh uncombusted fuel which them ignites. This cycle repeats itself many times per second and you end up with a sustained micro flame. The ratio of gases determines how many times per second ignition occurs and you can actually say that the flame has a frequency (I.e. You can hear the flame buzz while it is lit).

So in short, yes micro flames are possible, just not from a candle.


Tl;dr
Teeny candles don't work. Burn hydrocarbons in a ceramic combustor for super hot, buzzing micro flames. Science is awesome.