Provided the use of a water-insoluble modifier, in-situ modification of PVDF membranes is an ideal method for preparing low-biofouling membranes. We report the formation, characterization and low-biofouling performances of modified PVDF membranes prepared by vapor-induced phase separation for microalgae harvesting. Poly(styrene)-b-poly(ethylene glycol) methacrylate (PS-b-PEGMA) is used as antifouling material. After characterizing the physico-chemical properties of membranes by SEM, AFM, FT-IR, XPS, and tensile tester, their hydrophilicity was assessed. Hydration capability was importantly enhanced with copolymer content. Adsorption of bovine serum albumin (BSA), lysozyme (LY) and fibrinogen (FN) was tested to investigate the resistance of membranes to nano-biofouling. Best results were obtained with membrane prepared from a casting solution containing 4 wt% copolymer (PS-b-PEGMA-4). Bacterial attachment tests proved that membranes could also resist micro-biofouling. Flux recovery ratio after filtration of BSA with PS-b-PEGMA-4 membrane was higher than with a commercial hydrophilic PVDF membrane. Applied in microalgae harvesting, it was found that membranes could efficiently resist biofouling by microalgae (FRR=76.9% with PS-b-PEGMA-4), still enabling a rejection ratio over 99.7%. (C) 2015 Elsevier Ltd. All rights reserved.