Bismuth Hall probes with an active area in the mu m(2) and sub-mu m(2) (down to (100 x 100) nm(2)) range have been fabricated on SiO(2)/Si substrates. The structural and electrical properties of Bi films with a thickness of 20-90 nm were investigated. Critical values of the structural characteristics, at which the film resistivity dependences undergo a distinct change were found. The transition to low resistivity, good crystallinity and high degree of texturing were observed at a film thickness of 65 nm. The potential use of the Bi Hall sensor as a swell sensor for monitoring the swelling of stimuli-sensitive hydrogels was demonstrated. (C) 2010 Elsevier B.V. All rights reserved.