A single beam near-field laser trap for optical stretching, folding and rotation of erythrocytes.

To understand the fundamental mechanical and viscoelastic properties of RBCs, one needs laser tweezers in which cells can not only be trapped, but also be stretched, folded, and rotated. Stretching, folding and rotating an RBC is particularly important in order to reveal the shear elasticity of the RBC membrane. Here we show a single beam near-field laser trapping technique under focused evanescent wave illumination for optical stretching, folding and rotation of a single RBC. This multifunctional manipulation method will provide a new platform for measuring cell properties such as the membrane elasticity, viscoelasticity and deformability.