Optical tweezers

Optical tweezers offer a sophisticated and contactless way of studying small particles. A light beam is tightly focused with a high numerical aperture (NA) microscope objective to a small spot. The light beam intensity gradients generate forces and trap small particles under this illumination. The trapped objects may be manipulated by moving a sample stage or by changing different parameters of the trapping beam. The performance of the trap can be evaluated by calculating the trapping efficiency. It is dependent on the optical power after the objective as well as the forces generated by focused light.

Recent research is focused on measurement of aggregation/disaggregation properties of red blood cells. Research topics include also characterization of point and elliptical tweezers as well as elastic light scattering measurements from trapped particles and cells.

Red blood cell aggregation/disaggregation measurements. Illustration of experiment, (1) – RBCs are brought intact with two-channels of laser tweezers and held for fixed period in contact, (2) – One of trap is moved to disaggregate doublet, (3) – RBCs are fully disaggregated.


Seven red blood cells trapped along a straight line.


(a) Elastic light scattering from two spheres in the direction of an incident beam and (b) elastic light scattering from two spheres perpendicular to the incident beam. The small figures show the orientation of the objects in relation to the laser beam and a CCD camera image of the near-field light scattering distribution. Vertical polarization was used. The scale bar is 10 μm. M. Kinnunen et al. Optics Letters 36(18), 3554-3556 (2011)


K. Lee, A. V. Danilina, M. Kinnunen, I. Meglinski and A. V. Priezzhev, ” Probing the Red Blood Cells Aggregating Force with Optical Tweezers,” Journal of Selected Topics in Quantum Electronics 22(3), 7000106 (2016).

K. Lee, M. Kinnunen, A. V. Danilina, A. V. Priezzhev, V.D. Ustinov, I. Meglinski, S. Shin"Characterization of shear stress preventing the red blood cells from aggregation at the individual cells level and in whole blood sample", Journal of Biomechanics, in review.

K. Lee, M. Kinnunen, M. Khokhlova, E. Lyubin, A. Priezzhev, I. Meglinski, and A. Fedyanin, “Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions,” Journal of Biomedical Optics, in review.

K. Lee , M. Kinnunen , A.E. Lugovtsov , A.V. Priezzhev, A.V. Karmenyan , “Optical study of the dynamics and deformation of erythrocytes in the flow” Optoelectronics, Instrumentation and Data Processing, 50(5), 519-524 (2014).

A. Kauppila, M. Kinnunen, A. Karmenyan, and R. Myllylä, ”Measurement of the trapping efficiency of an elliptical optical trap with rigid and elastic objects,”  Applied Optics, 51(23), 5705-5712 (2012).

A. Kauppila, M. Kinnunen, A. Karmenyan, and R. Myllylä, ”Elastic light scattering measurements from multiple red blood cells in elliptical optical tweezers,” Proc. SPIE 8097, 80970K (2011). [PDF]

M. Kinnunen, A. Kauppila, A. Karmenyan, and R. Myllylä, ”Measurement of elastic light scattering from two optically trapped microspheres and red blood cells in a transparent medium,” Optics Letters 36(18), 3554-3556 (2011). [PDF]

A. Kauppila, M. Kinnunen, A. Karmenyan, and R. Myllylä, ”Elliptical optical tweezers for trapping a red blood cell aggregate,” Photonics Letters of Poland 3(3), 95-97 (2011). Awarded the cover of Photonics Letters of Poland, September 2011. [PDF]

M. Kinnunen, A. Kauppila, A. Karmenyan, and R. Myllylä, "Effect of the size and shape of a red blood cell on elastic light scattering properties at the single-cell level," Biomed. Opt. Express 2(7), 1803-1814 (2011). [PDF]

M. Collins, A. Kauppila, A.V. Karmenyan, L. Gajewski, K. Szewczyk, M. Kinnunen, R. Myllylä, “Measurements of light scattering from trapped particles,” Proc. SPIE 7376, 737619 (2010). [PDF]



Last updated: 9.9.2016