Although the lung is an obvious target for site-specific delivery of many therapeutics for respiratory airway diseases such as asthma, COPD, and cystic fibrosis, novel strategies are needed to avoid key physiologic barriers for efficient delivery and controlled release of therapeutics to the lungs. Specifically, deposition into the deep lung requires particles with a 1-5 {micro}m aerodynamic diameter; however, particles with a geometric diameter less than 6 {micro}m are rapidly cleared by alveolar macrophages. Additionally, epithelial, endothelial, and fibroblast cells prefer smaller (\nView larger version (15K):\norg.highwire.dtl.DTLVardef@1dcd1dcorg.highwire.dtl.DTLVardef@55e23eorg.highwire.dtl.DTLVardef@788c02org.highwire.dtl.DTLVardef@30161f_HPS_FORMAT_FIGEXP M_FIG C_FIG