So you got sweaty back from cycling ?? wow !! what a tragedy, I feel so sorry for you, you're lucky to be alive... Seriously OP you're making a big issue out of nothing... I've been using backpacks and messenger bags for over 8 years now. Does my back get sweaty ?? Sure it does. So what ??. I've come to accept sweating as something that's part of being a human. Sweating is one of the positive side-effects of exercise.