A ringshaped laser trap based on axicons Bing

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 Optoelectronics Computing Group

Photonics in Cell Based Bio-Chip Platforms Photonics to augment cell array chips e. g. , for pharmacological data extraction Photonics to augment m-fluidics chips e. g. , for sample purification or sorting Live Cells Biocompatible Environment Cell Array Platform 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 Optoelectronics Computing Group m-Fluidics Platform

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 measuring molecular-scale forces for single molecule study Multiple-step yeast manipulation [3] 1. 2. 3. 4. 5. Scanning laser line optophoresis [4] A. Ashkin, Physical Review Letters, v 24, p 154 -159, 1970. A. Ashkin, et al. , Optics Letters, v 11, n 5, p 288 -291, 1986. B. Shao et al. , accepted for publication, Sensors & Actuators B Chemical, , 2005. A. Forster et al. , Analytical biochemistry, v 327, p 14 -22, 2004. Koen Visscher, et al. , Nature, v 400, p 184 -189, 1999. Optoelectronics Computing Group Kinesin Moving on a Microtubule[5]

Optical Trapping Theory • 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. F Di a F Ri +z F Do FR o +r Photon Momentum Net Force b 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|. ØFor 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 Optoelectronics Computing Group * After A. Ashkin, Phys. Rev. Lett. , 24, 156 (1970)

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 Optoelectronics Computing Group High efficiency bio-tropism study under equal-distance condition

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. Optoelectronics Computing Group

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. Optoelectronics Computing Group 13. D. Mc. Gloin, et al. , Spie’s oemagazine, p 42 -45, Jan 2003. 14. I. Manek, et al. , Optics Communicatons, 147, p 67 -70, 1998.

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 Optoelectronics 7. B. Shao et al. , Proceedings of the SPIE, v 5514, p 62 -72, 2004. Computing Group

Ray Tracing Simulation ZEMAX simulation with 40 x NA 1. 3 oil immersion lens shows a ring-shaped focus at the sample plane whose diameter agrees with theoretical calculation~220 mm. 40 x Oil WD=0. 2 Water Immersion Oil 0. 20 mm 0. 077 mm f. FL=100 mm f. TL=400 mm Coverglass 0. 17 mm sample plane spot diagram Cross-section of annular focus Optoelectronics Computing Group

Ray Tracing Simulation Optoelectronics Computing Group

Experimental Setup Ytterbium l=1064 nm P 0 Axiovert 200 M Optoelectronics Computing Group

Experimental Setup Optoelectronics Computing Group

Experimental Results Experiment with microspheres verified the feasibility of the annular laser trap. 40× MO NA=1. 3 Oil (Zeiss) Ppost. MO=80 m. W 15 micron polystyrene beads (Duke Scientific) Rring~105 mm Buffer: Water 100 mm Formation of the ring of microspheres P~2. 4 m. W/microsphere Optoelectronics Computing Group Leftwards stage translation

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

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. Optoelectronics Computing Group

Optical System Design 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 axicon 2 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 Dr ring d Din Optoelectronics Computing Group

Simulation Results 80 mm D=486 mm D=84 mm Optoelectronics Computing Group

Experimental Setup Ytterbium l=1064 nm P 0 l=66~126 mm D=130~430 mm 40 x oil NA=1. 3 Power throughput: Optoelectronics Computing Group

Experimental Results 40 x Oil NA=1. 3 D~240 mm 15 mm polystyrene beads 100 mm da 2 -a 3=89 mm Pout=0. 5 W Ppost. MO=90 m. W Optoelectronics Computing Group D~135 mm 100 mm da 2 -a 3=68 mm Pout=0. 3 W Ppost. MO=55 m. W

Experimental Results P 0=12 W, Rring~55 mm Ptrap~70 m. W/sperm, 5× P 0=12 W, Rring~55 mm Ptrap~70 m. W/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. Optoelectronics Computing Group

Conclusions v 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 v A new application of axicon has been explored to build an annular laser trap which confines particles into a ring-shaped pattern. v 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. v 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. Optoelectronics Computing Group

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

References 1. http: //arbl. cvmbs. colostate. edu/hbooks/pathphys/reprod/semeneval/motility. html 2. Y. Tadir, et al. , Fertil. Steril. v 52, p 870 -873, 1989. 3. Y. Tadir, et al. , Fertil. Steril. v 53, p 944 -947, 1990. 4. P. Patrizio, et al. , Journal of Andrology, v 21, p 753 -756. 2000. 5. Z. N. Dantaset al. , Fertil. Steril. v 63, p 185 -188, 1995. 6. M. Eisenbach et al. , Bio. Essays, v 21, p 203 -210, 1999. 7. J. Vinson, et al. , Poster 5930 -79, Optics & Photonics, SPIE 50 th Annual Meeting, Jul. 31 -Aug. 4, San Diego, 2005. 8. B. Shao et al. , Proceedings of the SPIE, v 5514, p 62 -72, 2004. 9. A. Ashkin, Physical Review Letters, v 24, p 154 -159, 1970. 10. A. Ashkin, et al. , Optics Letters, v 11, n 5, p 288 -291, 1986. 11. Koen Visscher, et al. , Nature, v 400, p 184 -189, 1999. 12. A. Forster et al. , Analytical biochemistry, v 327, p 14 -22, 2004. 13. A. Birkbeck, et al. , Biomedical Microdevices, v 5, n 1, p 47 -54, 2003. 14. D. Mc. Gloin, et al. , Spie’s oemagazine, p 42 -45, Jan 2003. 15. I. Manek, et al. , Optics Communicatons, v 147, p 67 -70, 1998. Optoelectronics Computing Group