The size dependent contact behavior of nanoparticle agglomerates was studied. Size fractionated TiO2 nanoparticle agglomerates were synthesized with a combination of a flame spray reactor and a differential mobility analyzer resulting in four different agglomerate sizes (median values from 78 to 161 nm). Contact behavior of the fractionated agglomerates was investigated using atomic force microscopy. A model of the contact behavior of agglomerates under tensile stress was established in which the aggregates within the agglomerates rearrange and form chains before breakage. Force curves show that the length of the chains and the amount of rearrangements depend on the agglomerate sizes. Larger agglomerates require more work for their aggregate rearrangement before the final breakage is induced. (C) 2014 Elsevier B.V. All rights reserved.