1 Influence of Fines on the Surface Energy Heterogeneity of Lactose for Pulmonary Drug Delivery Raimundo Ho, a Adrian S. Muresan, b Gerald A. Hebbink, c and Jerry Y. Y. Heng a,* a Surfaces and Particle Engineering Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom b FrieslandCampina Research, Harderwijkerstraat 41006, 7418 BA Deventer, The Netherlands c FrieslandCampina DOMO, Hanzeplein 25, 8017 JD, Zwolle, The Netherlands * Corresponding author: Tel: +44 (0)20 7594 0784; Fax: +44 (0)20 7594 5638. E-mail address: jerry.heng@imperial.ac.uk (Jerry Y.Y. Heng)