Using molecular dynamics (MD) simulations, we report a displacing method to release encapsulated molecules out of open-ended single-walled carbon nanotubes (SWNTs). The simulations indicated that encapsulated molecules such as water, DNA and indomethacin (IMT) molecules would be expelled from SWNTs by fillers such as C60 molecules and metal nanowires through a displacement process, which is attributed to the much stronger van der Waals interaction between SWNTs and fillers than that between SWNTs and encapsulated molecules. In order to quantitatively reveal the release process, the center of mass (COM) distances between encapsulated molecules (and fillers) and SWNTs were calculated. Furthermore, investigations of various energies indicated that the release process is spontaneous and the van der Waals force is the main drive for the release process. Moreover, some influencing factors such as nanotube diameter and length are discussed as well. This study provides a new method for the release of drugs/genes in the biomedical field, and provides valuable information for designing novel assembled nanoscale devices.
