Nanoplasmonic 光学晶格中微粒子的俘获
Summary
我们描述了在 nanoplasmonic 光学晶格中光阱微粒子的过程。
Abstract
为了克服传统远场光学镊子的衍射极限, 研制了浆光学镊子。浆光学晶格由一组纳米结构组成, 它表现出各种俘获和传输行为。我们报告的实验程序, 捕获微粒子在一个简单的正方形 nanoplasmonic 光学晶格。我们还描述了 nanoplasmonic 阵列的光学设置和纳米。光学电位是通过照亮一组 980 nm 波长的高斯光束和令人兴奋的等离子体共振的金 nanodiscs 来产生的。通过荧光成像对颗粒的运动进行监测。此外, 还描述了一种抑制光热对流的方案, 以增加可用的光学功率, 从而获得最佳捕获。通过将试样冷却到低温, 并利用水介质的近零热膨胀系数, 实现了对流的抑制。这里报告了单粒子传输和多粒子捕获。
Introduction
微尺度微粒的光学捕获最初是由亚瑟在二十世纪七十年代代初提出的。自其发明以来, 该技术已被开发为微型和纳米1,2的多功能工具。传统的基于远场聚焦原理的光阱, 其空间约束中的衍射固有地受到限制, 其中俘获力显著减小 (在一个半径为粒子的a3定律之后)a)3. 为了克服这种衍射极限, 研究人员利用浆金属纳米结构, 开发了基于倏逝光场的近场光学俘获技术, 此外, 将纳米级物体捕获到单蛋白分子已被证明4,5,6,7,8,9,10,11。此外, 浆光学晶格是由周期性浆纳米结构的阵列创建的, 以赋予微纳米粒子和多粒子堆叠的长距离传输11,12。在光学晶格中干扰俘获的一个主要障碍是光热对流, 并已努力通过几个组14、15、16、17来阐明其效果。使用格林函数, Baffou et al.通过将每个浆纳米结构建模为点加热器来计算温度剖面, 然后通过实验验证了它们的模型14。汤森的小组也测量了等离子体诱导对流的粒子测速仪15。作者的小组也描绘了近场和对流运输并且显示了一项工程战略抑制光热对流16,17。
在这里, 我们提出了一个光学装置的设计和详细的程序, 专门用于诱捕实验浆光学晶格。光的潜力是通过照亮一组金 nanodiscs 与一个松散的聚焦高斯光束。这里还描述了一种通过将样品冷却到低温 (~ 4 ° c) 来抑制光热对流以获得最佳捕获的方案, 这里也介绍了17。在方程近似下, 由 u ~l2 gβΔT / v给出了自然对流速度u的数量级估计, 其中L是热源的长度刻度, δT是由于加热而引起的相对于参照的温度升高。 g和β分别是重力加速度和热膨胀系数。在接近4° c 的温度下, 水介质的密度表现出反常的温度依赖性, 这就转化为近零的热膨胀系数, 因此, 微乎其微小的光热效应对流。
Protocol
Representative Results
Discussion
此处描述的过程使读者能够可靠地每天复制陷印。一个通用的经验指南, 设计一个可用的晶格是使用一个可比大小的浆阵, interdisc 距离, 和被困粒子的大小。与单一的, 孤立的浆纳米结构相结合, 光学晶格设计与高光功率所提供的冷却样品到〜4° c 使用, 大大提高了捕获概率。如果分离性好, 浆纳米结构被用作诱捕点, 你需要等待很长时间才能将微粒迁移到浆纳米结构附近的有效俘获体积中。同时, 增…
Disclosures
The authors have nothing to disclose.
Acknowledgements
y.t.y. 愿意承认科技部在赠款数量最多 105-2221-007-MY3 和国立清华大学的资助支持下, 105N518CE1 和106N518CE1。
Materials
| Thermoelectric cooling element | Thorlabs | TEC 1.4-6 | TEC element for sample cooling |
| RTD thermometer | Omega Engineering | RTD Thermometer 969C | |
| Forward looking infrared camera | FLIR | FLIR One | IR camera for temperature monitoring |
| light emitting diode light source | Touchbright | Light source for illumination for fluorescent imaging | |
| Long working distance objective | Olympus | LMPLFLN | For illuminating the sample and imaging |
| Optical trap kit | Thorlabs | OTKB/M | |
| Cover slip | thickness 0.17 mm | ||
| Scanning electron microscope | Hitachi | SEM-Hitachi S3400N | |
| Electron beam blanker | DEBEN | PCD beam blanker | the blanker is added to the scanning electron microscope |
| Thermal evaporator | SYSKEY Technology | ||
| Mask aligner | Karl Suss | MJB 3 | For marker fabrication |
| Electron beam resist | Sigma Alrich | PMMA 120K | For e-beam lithography |
| Electron beam resist | Sigma Alrich | PMMA 960K | For e-beam lithography |
| Fluoresent labeled polystyrene microspheres | Polyscience | 2 um diameter | |
| Bipolar transistor | Mouser | 2N3904 | quantity 2 for TEC driver circuit |
| Bipolar transistor | Mouser | 2N3906 | quantity 2 for TEC driver circuit |
| MOSFET power transistor | Mouser | IRF5305 | quantity 2 for TEC driver circuit |
| MOSFET power transistor | Mouser | IRF131ON | quantity 2 for TEC driver circuit |
| 10 kOhm resistor | Mouser | quantity 6 for TEC driver circuit | |
| 910 Ohm resistor | Mouser | quantity 2 for TEC driver circuit | |
| Photoresist | Microchemicals | AZ4620 | For marker fabrication |
| Acetone | Sigma Alrich | For marker fabrication | |
| Fluorescence Module for the OTKB/M, Metric Threads | Thorlabs | OTKB-FL/M | |
| Fluorescent filter set | Thorlabs | MDF-FITC | For Fluorescein Isothiocyanate (FITC) |
| Ultrasonic cleaner | Delta | DC150H | For the lift off step |
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