Just prepare a substrate and place two posts. Place a glass pipette onto these two posts. Pour PDMS to cover the pipette. After fully cured, remove this pipette. You will create a buried rounded channel. Lung-hao Hu Graduate Student Dept.of Mechanical Engineering Univ.of Colorado Boulder UCB 427 CO 80309 U.S.A Email:lung.hu@colorado.edu Tel:303-786-1702(H) 303-492-6107(O) Fax:303-492-3498