[1] Univ Colorado Boulder, Biomed Engn Program, Boulder, CO 80303 USA
[2] Univ Colorado Boulder, Dept Mech Engn, Boulder, CO 80303 USA
[3] Univ Colorado, Morgan Adams Fdn Pediat Brain Tumor Res Program, Dept Pediat, Sch Med, Aurora, CO 80045 USA
[4] 1111 Engn Dr, Boulder, CO 80309 USA