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A ring-shaped laser trap based on axicons

A ring-shaped laser trap based on axicons. Bing Shao University of California, San Diego Del Mar Photonics August 3 rd , 2005. San Diego, CA Optics & Photonics 2005 The International Society for Optical Engineering. Photonics in Cell Based Bio-Chip Platforms. Live Cells. Biocompatible

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A ring-shaped laser trap based on axicons

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  1. A ring-shaped laser trap based on axicons Bing Shao University of California, San Diego Del Mar Photonics August 3rd, 2005 San Diego, CA Optics & Photonics 2005 The International Society for Optical Engineering

  2. Photonics in Cell Based Bio-Chip Platforms Live Cells Biocompatible Environment Cell Array Platform m-Fluidics Platform Photonics to augment cell arraychips e.g., for pharmacological data extraction Photonics to augment m-fluidics chips e.g., for sample purification or sorting • Key features of Photonics • Remote manipulation • reduces cross-contamination • wireless connectivity • Individual selectivity of single cells or particles • Fast, highly parallel processing • Independent of environment of cells or medium • Essentially harmless to bio-molecules

  3. Background on Optical Trapping • Discovered in 1970 [1] and demonstrated in 1986 [2] both by Ashkin, optical tweezers have been applied effectively for • Manipulation of biological cells, organelles and beads • Characterization and sorting of microparticles including cells • Generating and measuringmolecular-scale forcesfor single molecule study Multiple-step yeast manipulation [3] Scanning laser line optophoresis [4] Kinesin Moving on a Microtubule[5] • A. Ashkin, Physical Review Letters, v24, p154-159, 1970. • A. Ashkin, et al., Optics Letters, v11, n5, p288-291, 1986. • B. Shao et al., accepted for publication, Sensors & Actuators B Chemical,, 2005. • A. Forster et al., Analytical biochemistry, v327, p 14-22, 2004. • Koen Visscher, et al., Nature, v400, p184-189, 1999.

  4. Optical Trapping Theory +z FDi FDo +r a FRo FRi Net Force b • Optical tweezers form a stable three-dimensional trap that is created by the optical forces that arise in highly focused laser beams. • These optical forces can be attributed to the transfer of momentum of a photon that occurs while undergoing a scattering event such as reflection or refraction. Photon Momentum • Ray Optics Analysis for Large Particles (D >>l) • Refraction at boundary transfers photon momentum to particle • Force due to refraction(FD) is higher than that due to reflection (FR) • Restorative “trapping” force pushes particle toward z axis • Arises from the gradient in the Gaussian envelope of the beam such that |a| > |b|. • For a high NA lens, the gradient force will be in –z direction and acts to restore the object to the focal point as well as to the z axis resulting in a Single Beam Optical Trap * After A. Ashkin, Phys. Rev. Lett., 24, 156 (1970)

  5. A Ring trap • When studying self-propelling cells (e.g., sperm, algae, etc.) with single point trap, interference from untrapped cells need to be avoided. • A Ring trap based speed bump could be used as a force shield to protect analysis area from other cells. • Parallel sorting / separation of the cells based on their motility and response to attractants can be accomplished. • Only winners will make it to the attractant stimuli Facilitate single sperm study by preventing interference/competition High efficiency bio-tropism study under equal-distance condition

  6. Generating a uniform Ring Trap! • Mechanical scanning---moving part, speed limitation (especially for fast moving target), reduced average exposure time, tangential drag force introduced by scanning focus • Diffractive optics/Holography---lower efficiency, not suitable for power limiting system, dynamically adjustment of ring size and depth needs SLM. • Axicon---low cost, high efficiency, easy implementation, ring size dynamically adjustable Axicon (rotationally symmetric prism), is a lens composed of a flat surface and a conical surface.

  7. History of Axicon for Trapping 1. Diffraction-free Bessel beam[13](Gaussian+Axicon) Non-diffractive propagation distance for a quasi-Bassel beam 2. Hollow laser beam for atom trapping[14](Gaussian+Lens+Axicon) Provide a large and dark inner region and the available laser power is used in an optimum way for creating the repulsive optical wall. 13. D. McGloin,et al., Spie’s oemagazine, p42-45, Jan 2003. 14. I. Manek, et al., Optics Communicatons, 147, p67-70, 1998.

  8. How to use Axicons to trap particles in a ring? • Size---Trapping spot deviation from the optical axis d input beam inclination q[7]. • Uniformity---MO input is a cone of collimated beam intersecting at the back aperture with inclination angle q. • Strength---filling MO back aperture completely to ensure tight focusing  input light cone thickness = diameter of MO back aperture 7. B. Shao et al., Proceedings of the SPIE, v5514, p62-72, 2004.

  9. Ray Tracing Simulation ZEMAX simulation with 40x NA 1.3 oil immersion lens shows a ring-shaped focus at the sample plane whose diameter agrees with the theoretical calculation~220mm. 40x Oil WD=0.2 fFL=100mm fTL=400mm Water 0.077mm Immersion Oil 0.20mm Coverglass 0.17mm sample plane spot diagram Cross-section of annular focus

  10. Ray Tracing Simulation

  11. Experimental Setup Ytterbium l=1064nm P0 Axiovert 200M

  12. Experimental Setup

  13. Experimental Results 100mm Experiment with microspheres verified the feasibility of the annular laser trap. 40× MO NA=1.3 Oil (Zeiss) PpostMO=80mW 15 micron polystyrene beads (Duke Scientific) Buffer: Water Rring~105mm Formation of the ring of microspheres Leftwards stage translation P~2.4mW/microsphere

  14. Experimental Results Preliminary experiment with sperm shows an annular reaction zone (a) (b) Rring~105mm Ptrap~30mW/sperm (c) (d) Average trapping power: 100~200mW/sperm [6] 6. J. Vinson, et al., Poster 5930-79, Optics & Photonics, SPIE 50th Annual Meeting, Jul. 31-Aug.4, San Diego, 2005.

  15. Dynamically Adjustable Annular Trap? • With fixed total power, changing the size of the ring trap leads to a change of trapping power per spot. This could be used for quantitative evaluating and sorting self-propelling cells with different swimming forces, motility patterns, and chemotaxis responses to chemo-attractants. • The size of self-propelling cells varies dramatically. A variable annular trap enables study of different species without redesigning the system.

  16. Optical System Design d • Only q should be changed (normal telescope lens pair also changes Din)! • Introducing an axicon “telescope” pair in between the focusing lens and the tube lens • Shift axicon2 along the optical axis while fixing other optics • The incident angle q is varied correspondingly while the filling of the objective back aperture is almost not changed. DdDqDrring Din

  17. Simulation Results 80 mm D=486mm D=84mm

  18. Experimental Setup Ytterbium l=1064nm P0 P0 D=130~430mm l=66~126mm 40x oil NA=1.3 Power throughput:

  19. Experimental Results D~135mm D~240mm 100mm 100mm 40x Oil NA=1.3 15mm polystyrene beads Pout=0.3WPpostMO=55mW da2-a3=89mm Pout=0.5W PpostMO=90mW da2-a3=68mm

  20. Experimental Results P0=12W, Rring~55mm Ptrap~70mW/sperm, 5× P0=12W, Rring~55mm Ptrap~70mW/sperm, 3× Fast sperm: not affected, swim across Slow sperm: drawn to the ring and scattered out of the focus plane Dead sperm and red blood cells: stably trapped to the ring and can freely move along the circumference.

  21. Conclusions • Traditional applications of axicons lies in generating diffraction-free Bessel beam for communication or longitudinal partical confinement, and create central dark region for atom trapping • A new application of axicon has been explored to build an annular laser trap which confines particles into a ring-shaped pattern. • By adding two more axicons, and simply translating one of them along the optical axis, the diameter of the annular trap can be dynamically adjusted. • Although further optimization of the system is needed to improve the strength and stability of the annular trap, this system provides a prototype of an objective, automated, quantitative, and parallel tool for, cell motility and bio-tropism study.

  22. Acknowledgements Scripps Institute of Oceanography Beckman Laser Institute Beckman Center for Conservation and Research for Endangered Species (CRES) Zoological Society of San Diego

  23. References • http://arbl.cvmbs.colostate.edu/hbooks/pathphys/reprod/semeneval/motility.html • Y. Tadir, et al., Fertil. Steril. v52, p 870-873, 1989. • Y. Tadir, et al., Fertil. Steril. v53, p 944-947, 1990. • P. Patrizio, et al., Journal of Andrology, v21, p753-756. 2000. • Z. N. Dantaset al., Fertil. Steril. v63, p185-188, 1995. • M. Eisenbach et al., BioEssays, v21, p203-210, 1999. • J. Vinson, et al., Poster 5930-79, Optics & Photonics, SPIE 50th Annual Meeting, Jul. 31-Aug.4, San Diego, 2005. • B. Shao et al., Proceedings of the SPIE, v5514, p62-72, 2004. • A. Ashkin, Physical Review Letters, v24, p154-159, 1970. • A. Ashkin, et al., Optics Letters, v11, n5, p288-291, 1986. • Koen Visscher, et al., Nature, v400, p184-189, 1999. • A. Forster et al., Analytical biochemistry, v327, p 14-22, 2004. • A. Birkbeck, et al., Biomedical Microdevices, v5, n1, p47-54, 2003. • D. McGloin,et al., Spie’s oemagazine, p42-45, Jan 2003. • I. Manek, et al., Optics Communicatons, v147, p67-70, 1998.

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