Motion behavior of mammalian AT-SC under evanescent field illumination

The motion behavior of mammalian adipose tissue derived stem cells (AT-SCs) on an integrated channel waveguide under the evanescent field illumination is demonstrated and analyzed. The AT-SCs, suspended to a concentration of 1 x 10⁵ cells per ml, are deposited in a reservoir over a copper ion-exchanged channel waveguide. Light from a HeNe laser operating at 632.8nm was coupled into the waveguide, causing the cells under the illumination of evanescent field and moved in a skewed stochastic motion in accordance to the laser power. The trajectory angle of the motion of the cells towards the illuminated channel waveguide was investigated and analyzed to distinguish the factors that affect such behavior. The cells reach a position relative to the illuminated channel, which is dictated by the compounded effect of the convectional current and evanescent field. The observations deduced that motion due to the optical field exists and were more pronounced when considering the trajectory angle towards the output facet. However, the optical forces are not significantly large enough to counter the motion due to the convection current. The results are discussed in light of the potential application of optical channel waveguides for bioanalytical applications, namely in the identification, sorting and analysis of differently sized mammalian cells without recourse to fluorescence or antibody staining.