Name: Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications (Video) | JoVE Journal
Uploaded: 2017-06-02T15:00:00.000+00:00
Duration: 8 min 6 s
Description: Learn to fabricate polymer microspheres for optical resonators using vapor diffusion and interface precipitation methods. This technique enables energy-efficient production of laser devices and sensors.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

This work was partly supported by KAKENHI (25708020, 15K13812, 15H00860, 15H00986, 16H02081) from JSPS/MEXT Japan, the Asahi Glass Foundation, and the University of Tsukuba Pre-strategic initiative, "Ensemble of light with matters and life."

1. Fabrication Protocols of Polymer Microspheres
<ol>
	<li>Vapor Diffusion Method
	<ol>
		<li>Dissolve 2 mg of conjugated polymers, such as P1 (poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(5-octylthieno[3,4-c]pyrrole-4,6-dione-1,3-diyl)])28 and P2 (poly[(N-(2-heptylundecyl)carbazole-2,7-diyl)-alt-(4,8-bis[(dodecyl)carbonyl]benzo[1,2-b:4,5-b&#8242;]dithiophene-2,6-diyl)])28, in 2 mL of chloroform (a good solvent) in a 5-mL vial.</li>
		<li>Put 5 mL of methanol (a poor solvent) in a 50 mL vial.</li>
		<li>Put the 5 mL vial containing the chloroform solution of the polymer into the 50 mL vial containing methanol.</li>
		<li>Cap the 50 mL vial and keep it for 3 days at 25 &#176;C to allow for the precipitation of the polymer microspheres.</li>
	</ol>
	</li>
	<li>Mini-Emulsion Method
	<ol>
		<li>Dissolve 5 mg of conjugated polymers, such as poly[9,9-di-n-octylfluorenyl-2,7-diyl] (PFO) and poly[2-methoxy-5-(3&#39;,7&#39;-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMOPPV), in 1 mL of chloroform.</li>
		<li>Dissolve 30 mg (~50 mM) of sodium dodecyl sulfate (SDS) in 2 mL of deionized water.</li>
		<li>Add 100 &#181;L of the chloroform solution of the polymer to 2 mL of water containing SDS.</li>
		<li>Stir the chloroform/water mixture vigorously using an ultra-high-speed homogenizer at 30,000 rpm for 2 min to emulsify the solution.</li>
		<li>Keep it for 1 day without capping the vial to evaporate the chloroform.</li>
		<li>Centrifuge the dispersion in a 1.5 mL microcentrifuge tube for 5 min at 2,200 x g. Remove the supernatant aqueous solution containing SDS.</li>
		<li>Add 2 mL of deionized water and shake vigorously.</li>
		<li>Repeat step 1.2.6 and 1.2.7 thrice to wash out the residual SDS.</li>
	</ol>
	</li>
	<li>Interface Precipitation Method</li>
	<li>Dissolve 200 &#181;g of polystyrene (PS) and 10 &#181;g of fluorescent dye (boron dipyrrin, BODIPY) to 0.2 mL of tetrahydrofuran (THF).</li>
	<li>Gently pour the THF solution onto 1 mL of the water layer.</li>
	<li>Keep the two-layer separated THF/water for 6 h without capping the vial to allow for the precipitation of the polymer microspheres.</li>
</ol>
2. Micro-photoluminescence (&#181;-PL) Measurement
<ol>
	<li>Sample Preparation
	<ol>
		<li>Dilute a suspension of the microspheres prepared in section 1 in a non-solvent (i.e., methanol or deionized water).</li>
		<li>Spin-cast one drop (20-30 &#181;L) of the diluted suspension of the microspheres onto a quartz substrate using a spin-coater (typically, 2,000 rpm for 50 s).</li>
		<li>Air-dry the resultant casted film until the solvents have evaporated completely (~5 min).</li>
	</ol>
	</li>
	<li>Experimental Setup
	<ol>
		<li>Put the quartz substrate (15 x 15 x 0.5 mm3) on the sample stage of an optical microscope.</li>
		<li>Find well-defined microspheres that are isolated from other spheres and appropriate for the &#181;-PL measurement.</li>
		<li>Select a laser (i.e., wavelength, continuous wave or pulse, irradiation time, integration, etc.).</li>
		<li>Select the magnification of the lens.</li>
	</ol>
	</li>
	<li>Measurements
	<ol>
		<li>Use a focused laser beam to irradiate the microsphere. Use the following laser condition: cw or pulsed laser with excitation wavelengths (&#955;ex) of 405 nm (cw), 450 nm (cw), 355 nm (pulse laser; frequency, 1 kHz; pulse duration, 7 ns), and 470 nm (pulse laser; frequency, 2.5 MHz; pulse duration, 70 ps).</li>
		<li>Record the PL spectrum at the excited spot using a spectrometer with a grating of 300 or 1,200 grooves mm-1.</li>
		<li>Take a fluorescent image.</li>
		<li>Change the excitation spot by moving the sample stage.</li>
		<li>Change the detection spot by tilting the collimator (if necessary).</li>
	</ol>
	</li>
</ol>
3. Micromanipulation Technique
<ol>
	<li>Manipulation of Microspheres
	<ol>
		<li>Set a quartz substrate upon which the microspheres are immobilized on the sample stage of an optical microscope.</li>
		<li>Find a well-defined microsphere appropriate for the &#181;-PL measurement.</li>
		<li>Set a plastic micro-needle on a micro-manipulation apparatus.</li>
		<li>Move the micro-needle using a computer-controlled joystick to pick up a microsphere.</li>
		<li>Move the microsphere and connect it to another microsphere.</li>
		<li>Measure the &#181;-PL from the connected microsphere.</li>
	</ol>
	</li>
</ol>

<ol><li>Ford, W. T., Chandran, R., Turk, H. <a target="_blank" href="https://www.iupac.org/publications/pac/60/3/0395/index.html">Catalysts Supported on Polymer Colloids.</a> Pure Appl. Chem. 60 (3), 395-400 (1988).</li>
<li>Chen, C. -W., Chen, M. -Q., Serizawa, T., Akashi, M. <a target="_blank" href="http://pubs.rsc.org/en/Content/ArticleLanding/1998/CC/A800203G#!divAbstract">In Situ Synthesis And the Catalytic Properties of Platinum Colloids on Polystyrene Microspheres with Surface-Grafted Poly(N-isopropylacrylamide).</a> Chem. Commun. , 831-832 (1998).</li>
<li>Suzuki, K., Yumura, T., Mizuguchi, M., Tanaka, Y., Chen, C. -W., Akashi, M. <a target="_blank" href="http://jglobal.jst.go.jp/en/public/20090422/200902160713409722">Poly(N-isopropylacrylamide)-Grafted Silica as a Support of Platinum Colloids: Preparation Method, Characterization, and Catalytic Properties in Hydrogenation.</a> J. Appl. Polym. Sci. 77, 2678-2684 (2000).</li>
<li>Zhang, S., Chen, L., Zhou, S., Zhao, D., Wu, L. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/cm1002274">Facile Synthesis of Hierarchically Ordered Porous Carbon via in Situ Self-Assembly of Colloidal Polymer and Silica Spheres and Its Use as a Catalyst Support.</a> Chem. Mater. 22, 3433-3440 (2010).</li>
<li>Kataoka, K., Harada, A., Nagasaki, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Block+Copolymer+Micelles+for+Drug+Delivery%3A+Design+Characterization+And+Biological+Significance%5BTitle%5D)+AND+%22Adv.+Drug+Deliv.+Rev%22%5BJournal%5D)">Block Copolymer Micelles for Drug Delivery: Design Characterization And Biological Significance.</a> Adv. Drug Deliv. Rev. 47, 113-131 (2001).</li>
<li>Otsuka, H., Nagasaki, Y., Kataoka, K. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((EGylated+Nanoparticles+for+Biological+And+Pharmaceutical+Applications%5BTitle%5D)+AND+%22Adv.+Drug+Deliv.+Rev%22%5BJournal%5D)">EGylated Nanoparticles for Biological And Pharmaceutical Applications.</a> Adv. Drug Deliv. Rev. 55, 403-419 (2003).</li>
<li>Nishiyama, N., Kataoka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Current+State%2C+Achievements%2C+And+Future+Prospects+of+Polymeric+Micelles+as+Nanocarriers+for+Drug+and+Gene+Delivery%5BTitle%5D)+AND+%22Pharmacol.+Ther%22%5BJournal%5D)">Current State, Achievements, And Future Prospects of Polymeric Micelles as Nanocarriers for Drug and Gene Delivery.</a> Pharmacol. Ther. 112, 630-648 (2006).</li>
<li>Velev, O. D., Kaler, E. W. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/la981729c">In Situ Assembly of Colloidal Particles into Miniaturized Biosensors.</a> Langmuir. 15 (11), 3693-3698 (1999).</li>
<li>Techawanitchai, P., Yamamoto, K., Ebara, M., Aoyagi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surface+Design+with+Self-Heating+Smart+Polymers+for+On-Off+Switchable+Traps%5BTitle%5D)+AND+%22Sci.+Technol.+Adv.+Mater%22%5BJournal%5D)">Surface Design with Self-Heating Smart Polymers for On-Off Switchable Traps.</a> Sci. Technol. Adv. Mater. 12, 044609(2011).</li>
<li>Lange, U., Roznyatovskaya, N. V., Mirsky, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Conducting+Polymers+in+Chemical+Sensors+And+Arrays%5BTitle%5D)+AND+%22Anal.+Chim.+Acta%22%5BJournal%5D)">Conducting Polymers in Chemical Sensors And Arrays.</a> Anal. Chim. Acta. 614, 1-26 (2008).</li>
<li>Rajesh, T., Kumar, D. <a target="_blank" href="https://www.researchgate.net/publication/257938771_Recent_progress_in_the_development_of_nano-structured_conducting_polymersnanocomposites_for_sensor_applications">Recent Progress in the Development of Nano-Structured Conducting Polymers/Nanocomposites for Sensor Applications.</a> Sens. Actuators B. 136, 275-286 (2009).</li>
<li>Wu, C., Szymanski, C., Cain, Z., McNeill, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Conjugated+Polymer+Dots+for+Multiphoton+Fluorescence+Imaging%5BTitle%5D)+AND+%22J.+Am.+Chem.+Soc%22%5BJournal%5D)">Conjugated Polymer Dots for Multiphoton Fluorescence Imaging.</a> J. Am. Chem. Soc. 129, 12904-12905 (2007).</li>
<li>Feng, L., Zhu, C., Yuan, H., Liu, L., Lv, F., Wang, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Conjugated+Polymer+Nanoparticles%3A+Preparation%2C+Properties%2C+Functionalization+And+Biological+Applications%5BTitle%5D)+AND+%22Chem.+Soc.+Rev%22%5BJournal%5D)">Conjugated Polymer Nanoparticles: Preparation, Properties, Functionalization And Biological Applications.</a> Chem. Soc. Rev. 42, 6620-6634 (2013).</li>
<li>Pecher, J., Mecking, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nanoparticles+of+Conjugated+Polymers%5BTitle%5D)+AND+%22Chem.+Rev%22%5BJournal%5D)">Nanoparticles of Conjugated Polymers.</a> Chem. Rev. 110, 6260-6279 (2010).</li>
<li>McGehee, M. D., Heeger, A. J. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/1521-4095(200011)12:22%3C1655::AID-ADMA1655%3E3.0.CO;2-2/abstract">Semiconducting (Conjugated) Polymers as Materials for Solid-State Lasers.</a> Adv. Mater. 12, 1655-1668 (2000).</li>
<li>Samuel, I. D. W., Turnbull, G. A. <a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/17385928">Organic Semiconductor Lasers.</a> Chem. Rev. 107, 1272-1295 (2007).</li>
<li>Kuehne, A. J. C., Gather, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Organic+Lasers%3A+Recent+Developments+on+Materials%2C+Device+Geometries%2C+and+Fabrication+Techniques%5BTitle%5D)+AND+%22Chem.+Rev%22%5BJournal%5D)">Organic Lasers: Recent Developments on Materials, Device Geometries, and Fabrication Techniques.</a> Chem. Rev. 116, 12823-12864 (2016).</li>
<li>Furumi, S., Kanai, T., Sawada, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Widely+Tunable+Lasing+in+a+Colloidal+Crystal+Gel+Film+Permanently+Stabilized+by+an+Ionic+Liquid%5BTitle%5D)+AND+%22Adv.+Mater%22%5BJournal%5D)">Widely Tunable Lasing in a Colloidal Crystal Gel Film Permanently Stabilized by an Ionic Liquid.</a> Adv. Mater. 23, 3815-3820 (2011).</li>
<li>Mikosch, A., Ciftci, S., Kuehne, A. J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Colloidal+Crystal+Lasers+from+Monodisperse+Conjugated+Polymer+Particles+via+Bottom-Up+Coassembly+in+a+Sol-Gel+Matrix%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Colloidal Crystal Lasers from Monodisperse Conjugated Polymer Particles via Bottom-Up Coassembly in a Sol-Gel Matrix.</a> ACS Nano. 10, 10195-10201 (2016).</li>
<li>Oraevsky, A. N. Whispering-Gallery Waves. Quant Electron. 32 (5), 377-400 (2002).</li>
<li>Yamamoto, Y. <a target="_blank" href="http://www.nature.com/pj/journal/v48/n11/full/pj201681a.html">Spherical Resonators from π-Conjugated Polymers.</a> Polym. J. 48, 1045-1050 (2016).</li>
<li>Adachi, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Spherical+Assemblies+from+%CF%80+-Conjugated+Alternating+Copolymers%3A+Toward+Optoelectronic+Colloidal+Crystals%5BTitle%5D)+AND+%22J.+Am.+Chem.+Soc%22%5BJournal%5D)">Spherical Assemblies from π -Conjugated Alternating Copolymers: Toward Optoelectronic Colloidal Crystals.</a> J. Am. Chem. Soc. 135, 870-876 (2013).</li>
<li>Tong, L., et al. <a target="_blank" href="http://pubs.rsc.org/en/content/articlelanding/2014/py/c4py00023d#!divAbstract">Tetramethylbithiophene in π-Conjugated Alternating Copolymers as an Effective Structural Component for the Formation of Spherical Assemblies.</a> Polym. Chem. 5, 3583-3587 (2014).</li>
<li>Tabata, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Self-Assembled+Conjugated+Polymer+Spheres+as+Fluorescent+Microresonators%5BTitle%5D)+AND+%22Sci.+Rep%22%5BJournal%5D)">Self-Assembled Conjugated Polymer Spheres as Fluorescent Microresonators.</a> Sci. Rep. 4, 5902(2014).</li>
<li>Kushida, S., et al. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/acs.macromol.5b00707">Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers.</a> Macromolecules. 48, 3928-3933 (2015).</li>
<li>Kushida, S., Braam, D., Lorke, A., Yamamoto, Y. <a target="_blank" href="http://aip.scitation.org/doi/abs/10.1063/1.4938854">Whispering Gallery Mode Photoemission From Self-Assembled Poly-Paraphenylenevinylene Microspheres.</a> AIP Conf. Proc. ICCMSE. 1702, 090046(2015).</li>
<li>Braam, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Optically+Induced+Mode+Splitting+in+Self-Assembled%2C+High+Quality-Factor+Conjugated+Polymer+Microcavities%5BTitle%5D)+AND+%22Sci.+Rep%22%5BJournal%5D)">Optically Induced Mode Splitting in Self-Assembled, High Quality-Factor Conjugated Polymer Microcavities.</a> Sci. Rep. 6, 19635(2016).</li>
<li>Kushida, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Conjugated+Polymer+Blend+Microspheres+for+Efficient+Long-Range+Light+Energy+Transfer%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Conjugated Polymer Blend Microspheres for Efficient Long-Range Light Energy Transfer.</a> ACS Nano. 10, 5543-5549 (2016).</li>
<li>Kushida, S., et al. <a target="_blank" href="http://pubs.rsc.org/en/Content/ArticleLanding/2016/RA/c6ra10662e#!divAbstract">Self-Assembled Polycarbazole Microspheres as Single-Component, White-Colour Resonant Photoemitters.</a> RSC Adv. 6, 52854-52857 (2016).</li>
<li>Aikyo, Y., et al. <a target="_blank" href="http://www.journal.csj.jp/doi/abs/10.1246/cl.160504">Enwrapping Conjugated Polymer Microspheres with Graphene Oxide Nanosheets.</a> Chem. Lett. 45, 1024-1026 (2016).</li>
<li>Landfester, K., et al. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/1521-4095(20020503)14:9%3C651::AID-ADMA651%3E3.0.CO;2-V/abstract">Semiconducting Polymer Nanospheres in Aqueous Dispersion Prepared by a Miniemulsion Process.</a> Adv. Mater. 14, 651-655 (2002).</li>
<li>Okada, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Color-Tunable+Resonant+Photoluminescence+and+Cavity-Mediated+Multistep+Energy+Transfer+Cascade%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Color-Tunable Resonant Photoluminescence and Cavity-Mediated Multistep Energy Transfer Cascade.</a> ACS Nano. 10, 7058-7063 (2016).</li>
<li>Pecher, J., Mecking, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nanoparticles+of+Conjugated+Polymers%5BTitle%5D)+AND+%22Chem.+Rev%22%5BJournal%5D)">Nanoparticles of Conjugated Polymers.</a> Chem. Rev. 110, 6260-6279 (2010).</li>
<li>Gather, M. C., Yun, S. H. <a target="_blank" href="http://www.nature.com/nphoton/journal/v5/n7/full/nphoton.2011.99.html">Single-Cell Biological Lasers.</a> Nat. Photon. 5, 406-410 (2011).</li>
<li>Schubert, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Lasing+within+Live+Cells+Containing+Intracelluler+Optical+Microresonators+for+Barcode-Type+Cell+Tagging+and+Tracking%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">Lasing within Live Cells Containing Intracelluler Optical Microresonators for Barcode-Type Cell Tagging and Tracking.</a> Nano Lett. 15, 5647-5652 (2015).</li>
</ol>

The authors declare no competing financial interests.

The selection of a good solvent and non-solvent is very important for the self-assembly of well-defined microspheres. If the solubility of a polymer is too high, precipitation will not occur. Also, in general, &#960;-conjugated polymers are hydrophobic, so polar non-solvents, such as MeOH, acetonitrile, and acetone, are often used in the vapor diffusion method to minimize the surface energy required to form a spherical shape. The interface precipitation method is often adopted for the preparation of dye-doped polymer mic...

Polymer nano/micro-sized particles are widely used for a variety of applications, including as catalyst support, column chromatography fillers, drug delivery agents, fluorescent probes for cell tracking, optical media, and so forth1,2,3,4,5,6,7,8,9. In particular, &#960;-conjugated polymers have inherent luminescent and charge conducting properties that are beneficial to optical, electronic, and optoelectronic applications using polymer spheres10,11,12,13,14, especially laser applications using soft organic materials15,16,17. For example, the three-dimensional integration of spheres with several hundred nanometer diameters forms colloidal crystals, which show photonic band gaps at a certain wavelength18,19. When light is confined in the intersphere periodic structure, lasing action appears at the middle of the stop band. On the other hand, when the size of the spheres increases to the several-micrometer scale, light is confined inside a single microsphere via total internal reflection at the polymer/air interface20. Propagation of the light wave at the maximum circumference results in interference, leading to the appearance of a resonant mode with sharp and periodic emission lines. These optical modes are so-called &#34;whispering gallery modes&#34; (WGMs). The term &#34;whispering gallery&#34; originated from St. Paul&#39;s Cathedral in London, where sound waves propagate along the circumference of the wall, allowing whispers to be heard by a person on the other side of the gallery. Because the wavelength of light is on the sub-micrometer scale, which is far smaller than sound waves, such a large dome is not necessary for the WGM of light: tiny, micrometer-scale, well-defined vessels, such as microspheres, microdiscs, and microcrystals, fulfill the WGM conditions.
Equation 1 is a simple form of the WGM resonating condition21:
n&#960;d = l&#955;&#160;&#160;&#160;&#160;&#160; (1)
where n is the refractive index of the resonator, d is the diameter, l is the integer number, and &#955; is the wavelength of the light. The left part of (1) is the optical path length through one circle propagation. When the optical path coincides with the integer multiple of the wavelength, resonance occurs, while at the other wavelength, the light wave is diminished upon rounding.
This paper introduces several experimental methods to prepare microspheres for WGM resonators from conjugated polymers in solution: vapor diffusion22,23,24,25,26,27,28,29,30, mini-emulsion31, and interface precipitation32. Each method has unique characteristics; for example, the vapor diffusion method affords well-defined microspheres with very high sphericity and smooth surfaces, but only low-crystallinity polymers can form these microspheres. On the other hand, for the mini-emulsion method, various kinds of conjugated polymers, including high-crystalline polymers, can form spheres, but the surface morphology is inferior to that obtained from the vapor diffusion method. The interface precipitation method is preferable for creating microspheres from dye-doped, non-conjugated polymers. In all cases, the selection of the solvent and the non-solvent plays an important role in the formation of spherical morphology.
In the second half of this paper, &#181;-PL and micro-manipulation techniques are presented. For the &#181;-PL technique, microspheres are dispersed on a substrate, and a focused laser beam, through a microscope lens, is used to irradiate a single isolated microsphere24. The generated PL from a sphere is detected by a spectrometer through the microscope lens. Moving the sample stage can vary the position of the excitation spot. The detection point is also variable by tilting the collimator optics of the excitation laser beam with respect to the optical axis of the detection path28,32. To investigate intersphere light propagation and wavelength conversion, the micro-manipulation technique can be used32. To connect several microspheres with different optical properties, it is possible to pick up one sphere using a micro-needle and put it on another sphere. In conjunction with the micromanipulation techniques and the &#181;-PL method, various optical measurements can be carried out using conjugated polymer spheres, which are prepared by a simple self-assembly method. This video paper will be useful to readers who wish to use soft polymer materials for optical applications.

<table><tbody><tr><td>polystyrene</td><td>Aldrich</td><td>132427-25G</td><td></td></tr><tr><td>sodium dodecylsulfate</td><td>Kanto Kagaku</td><td>372035-31</td><td></td></tr><tr><td>tetrahydrofuran</td><td>Wako</td><td>206-08744</td><td></td></tr><tr><td>chloroform</td><td>Wako</td><td>038-18495</td><td></td></tr><tr><td>methanol</td><td>Wako</td><td>139-13995</td><td></td></tr><tr><td>Poly(9,9-di-n-octylfluorenyl-2,7-diyl)</td><td>Aldrich</td><td>571652-500MG</td><td></td></tr><tr><td>Poly[2-methoxy-5-(3&amp;prime;,7&amp;prime;-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMOPPV)</td><td>Aldrich</td><td>546461-1G</td><td></td></tr><tr><td>poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(5-octylthieno[3,4-c]pyrrole-4,6-dione-1,3-diyl)] (P1)</td><td>synthesized</td><td>-</td><td>reference 28</td></tr><tr><td>poly[(N-(2-heptylundecyl)carbazole-2,7-diyl)-alt-(4,8-bis[(dodecyl)carbonyl]benzo[1,2-b:4,5-b&amp;prime;]dithiophene-2,6-diyl)] (P2)</td><td>synthesized</td><td>-</td><td>reference 28</td></tr><tr><td>fluorescent dye (boron dipyrrin; BODIPY)</td><td>synthesized</td><td>-</td><td>reference 32</td></tr><tr><td>Optical Microscope</td><td>Nicon</td><td>Eclipse LV-N</td><td></td></tr><tr><td>laser_405 nm</td><td>Hutech</td><td>DH405-10-5</td><td></td></tr><tr><td>Spectrometer</td><td>Lambda Vision</td><td>LV-MC3/T</td><td></td></tr><tr><td>Homogenizer</td><td>Microtech Nichion</td><td>Physcotron NS-360D</td><td></td></tr><tr><td>micromanipulation</td><td>Microsupport</td><td>Quick Pro QP-3RH</td><td></td></tr></tbody></table>

fabrication of polymer microspheres for optical resonator and laser applications

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Figure 1 shows schematic representations of the vapor diffusion method (a), mini-emulsion method (b), and interface precipitation method (c). For the vapor diffusion method (Figure 1a), a 5 mL vial containing a CHCl3 solution of polymers (0.5 mg mL-1, 2 mL) was placed in a 50 mL vial containing 5 mL of a non-solvent, such as MeOH. The outside vial was capped and then allowed to stand for 3 days at 25 °C. The...

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

The overall goal of this procedure is to produce optical microresonators for laser devices, optical circuits, and chemical and biological optical sensors. This method can help answer key questions in the functional polymer material sphere such as polymer optics, optoelectronics, and electronics. The main advantage of this simple and low energy consumption technique is that it uses functional polymers to fabricate optical resonators which have both optical and electrical properties.Demonstrating the procedure will be Mr.Okada, Mr.Zakarias, and Mr.Oki, graduate students from my laboratory. To begin the vapor diffusion method for this procedure, add five milliliters of methanol to a 50 milliliter vial. Next, dissolve two milligrams of conjugated polymers in two milliliters of chloroform in a five milliliter vial.Carefully place the five milliliter vial inside the 50 milliliter vial. After this, cap the 50 milliliter vial. Incubate at 25 degrees Celsius for three days to precipitate the polymer microspheres.To begin the mini-emulsion method, dissolve five milligrams of conjugated polymers in one milliliter of chloroform. Then, dissolve 30 milligrams of SDS in two milliliters of deionized water. Add 100 microliters of the polymer mixture to the SDS solution.Using an ultra high speed homogenizer, stir for two minutes at 30, 000 RPM. Allow the emulsion to rest for one day without the cap to evaporate the chloroform. The next day, centrifuge the dispersion in a 1.5 milliliter centrifuge tube for five minutes at 2, 200 times g.After removing the supernatant, add one milliliter of deionized water and shake vigorously. Repeat the centrifugation, supernatant removal, and water wash three times to completely remove any residual SDS. To begin the interface precipitation method, dissolve 20 milligrams of polystyrene in one milligram of fluorescent dye in 20 milliliters of tetrahydrofuran.Add one milliliter of deionized water to an empty 1.5 milliliter microtube. Then, gently pour 0.2 milliliters of the THF solution onto the water layer, being careful to keep the layers from mixing together. Allow the vial to rest for six hours without the cap to precipitate the polymer microspheres.To begin, dilute a suspension of prepared microspheres by 10 times with a poor solvent such methanol or deionized water. Using a spin coater, spin cast one drop of the diluted suspension onto a quartz substrate. Air dry the resulting casted film until the solvents have evaporated completely.Then, transfer the quartz substrate to the sample stage of an optical microscope. Identify an isolated and well-defined microsphere for micro-photoluminescence measurement. Set the laser conditions as outlined in the text protocol and use a focused laser beam to irradiate the microsphere.Using a spectrometer, record the photoluminescence spectrum. Next, take a fluorescent image of the irradiated microsphere. To begin, place the quartz substrate onto the sample stage of an optical microscope.Identify a single well-define microsphere. Then, set a tungsten microneedle on a micromanipulation apparatus. Using a touch panel controller, move the microneedle and pick up the microsphere.Connect the collected microsphere to another single well-defined microsphere. After this, irradiate the microsphere with a focused laser beam. Use a spectrometer to record the photoluminescence spectrum.Then, take a fluorescent image of the irradiated microspheres. In this study, well-defined polymer microspheres are fabricated using three different methods. The vapor diffusion method, the mini-emulsion method, and the interface precipitation method.Scanning electron microscopy shows that the vapor diffusion and interface precipitation methods produce microspheres with very smooth surface morphology. However, those obtained from the mini-emulsion method are rough because the surfactant covers the whole surface. The whispering gallery mode's photoluminescence is then recorded for a single microsphere of polymer one, polymer two, and their blend.The Q factor was seen to reach as 2, 200 for polymer one. Microspheres composed of polymer two however only reached as high as 300, possibly because of their rough surface morphology. Microspheres composed of the polymer blend maintained a high Q factor of 1, 500 likely because of its smooth morphology.Polymorphic polaron dye-doped polystyrene microspheres with photoluminescent colors of green, yellow, orange, and red were connected forming tetraspheres to investigate the intersphere energy transfer cascade. The light energy transfer from green to yellow and from yellow to orange is seen to be efficient while the energy transfer from orange to red did not occur because of the small overlap between the photoluminescent band of the energy donor and the adsorption band of the energy acceptor. Therefore, upconverted energy transfers such as from red to orange, yellow, and green hardly occur.While attempting this procedure, it is important to remember to avoid shaking the vials which may cause a rapid precipitation leading to ill-defined aggregates. Following this procedure, other method like emulsion polymerization and dispersion polymerization methods can be performed in order to answer additional questions like how to prepare monodisperse polymer spheres for application to colloidal photonic crystals. After its development, this technique paved the way for researchers in the field of polymer science to explore optical and laser applications using functional polymers.After watching this video, you should have a good understanding of how to prepare microoptical resonators by bottom up self-assembly process. Don't forget that working with laser devices have to take special care to protect from laser beams that harms your eyes.

fabrication-polymer-microspheres-for-optical-resonator-laser

Research

JoVE Journal

Engineering

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids.  The reflow method removes surface imperfections, allowing long photon lifetimes within both devices.  The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

Fabrication of Silica Ultra High Quality Factor Microresonators

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 μm diameter indium wires separated by ~100 μm, which exhibit a terahertz plasmonic response.

Fabricating Metamaterials Using the Fiber Drawing Method

A high-sensitivity photonic micro sensor was developed for electric field detection. The sensor exploits the optical modes of a dielectric sphere. Changes in the external electric field perturb the sphere morphology leading to shifts in its optical modes. The electric field strength is measured by monitoring these optical shifts.

Development of Whispering Gallery Mode Polymeric Micro-optical Electric Field Sensors

We develop and characterize a disordered polymer optical fiber that uses transverse Anderson localization as a novel waveguiding mechanism. This microstructured fiber can transport a small localized beam with a radius that is comparable to the beam radius of conventional optical fibers.

Fabrication and Characterization of Disordered Polymer Optical Fibers for Transverse Anderson Localization of Light

Two adjacent fluids passing through a grooved microfluidic channel can be directed to form a sheath around a prepolymer core; thereby determining both shape and cross-section. Photoinitiated polymerization, such as thiol click chemistry, is well suited for rapidly solidifying the core fluid into a microfiber with predetermined size and shape.

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility Χ(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS).

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

This work provides a method for the fabrication of droplet-based microfluidic platforms and the application of polyacrylamide microspheres for microsphere-PCR amplification. The microsphere-PCR method makes it possible to obtain single-stranded DNA amplicons without separating double-stranded DNA.

A Droplet-Based Microfluidic Approach and Microsphere-PCR Amplification for Single-Stranded DNA Amplicons

This protocol describes the fabrication of an implantable integrated imaging window using 3D laser printing. The window consists of a system of microlenses coupled with micro-scaffolds. The method involves two-photon polymerization (2PP) of the biocompatible photoresist SZ2080 in a continuous sequence, optimizing manufacturing efficiency and alignment between the different components.

Microfabrication of Implantable Optics Integrated in a Microstructured Imaging Window for Advanced In Vivo Imaging

Learn to fabricate polymer microspheres for optical resonators using vapor diffusion and interface precipitation methods. This technique enables energy-efficient production of laser devices and sensors.

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

Explore More Videos