Need a Water Insoluble Wick for Herbal Mosquito Repellent

Just about any natural fibre.
Cotton, wool, hamp, jute, linen etc
Plants and animals don't generally dissolve in the rain which is a reasonable indicator that their products won't either.
Del

Those natural fibers wont be able to inseminate the liquid through the wick when heat is applied to them.

That's odd as they've worked for centuries in oil lamps and candles
Del

I am not going to ignite it. It will receive heat through the vaporizing machine. So they might get shrink when they receive the heat. moreover i have not provided any source for ignition.

Capillary action doesn't rely on heat.
When I was a kid my Mum used to have these air fresheners called Airwick, it was a BIG FAT fibreous wick on a wire frame imersed in a bottle of stuff, you took the lid off and pulled the wire frame/wick assembly up, it was a tightish fit in the neck of the bottle so it wiped off surplus liquid as it was raised. It provided a large surface area and probably drew up further liquid by capillary action.
I think you need to do some practical experiments, I also think you are confusing the vapouristion effect of heat and the effect of capillary action.
My work here is done.
Del <swishes tail and dissapears monitor left>

thank you . i will try this out.

Take a look at polypropylene mesh. It's used to make filters for many chemical processes.

Seems like a strip of plain old kitchen sponge would work. The kind you use to wash dishes.

Cotton is insoluble in water and is used for candle wicking. Welting is made in a thicker cord. Thread, string, twine, or rope, all are obtainable in cotton and are capable of wicking and insoluble in water and most solvents.