well a bit more to it than that but check out the link for the details.you need more than a stick of course but nothing that you could not carry in a BOB or have around the house.
college students ran the tests and had %99 effective results.
four quarts a day with one unit and they sound easy to make.
plastic tubes,hose clamps,glue and no rocket science needed.
http://phys.org/news/2014-02-filter-sapwood-tree.html one of the guys at bwca.com sent in this link to the paper on the stick filter this morning
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0089934
clears up a lot of questions.