We present a simple method to control the tribological properties of contacts between polymer brushes and a solid counter surface. We show, using atomic force microscopy (AFM) experiments, that the friction force, upon relative sliding of a poly(N-isopropyl acrylamide) (PNIPAM) brush and a gold colloid on an AFM cantilever, varies over two orders of magnitude when changing the composition of an ethanol-water mixture that solvates the brush. We achieve this large variation in friction via a co-non-solvency effect: In pure water or ethanol, the PNIPAM brush is swollen and the friction is low, while in a 10-90 vol % ethanol-water mixture, the brush is partly collapsed and polymer-stretching causes the friction to be high. (C) 2016 Elsevier Ltd. All rights reserved.