C. F. Wilson, G. J. Simpson, D. T. Chiu, A. Stromberg, O. Orwar, N. Rodriguez, and R. N. Zare,”Nanoengineered Structures for Holding and Manipulating Liposomes and Cells,”Anal. Chem. 73, 787-791 (2001). C. F. Wilson, G. J. Simpson, D. T. Chiu, A. Stromberg, O. Orwar, N. Rodriguez, and R. N. Zare,”Nanoengineered Structures for Holding and Manipulating Liposomes and Cells,”Anal. Chem. 73, 787-791 (2001).