【摘要】：自光鑷技術(shù)問世以來,人們已經(jīng)熟練使用各種激光光束對(duì)微納米介電粒子及納米尺度的金屬粒子進(jìn)行三維捕獲和操控,并利用被捕獲的粒子作為手柄,探索生物體內(nèi)單細(xì)胞、單分子的未解之謎。在光鑷早期發(fā)展歷史上,其通常捕獲的對(duì)象為純介電微球和純金屬納米球。由于其各向同性的光學(xué)性質(zhì),通常被牢牢地捕獲在光阱中,因此很難觀測(cè)到其在微觀世界中豐富多彩的運(yùn)動(dòng)形態(tài)。而對(duì)于介電和金屬性質(zhì)結(jié)合為一體的非對(duì)稱顆粒,比如半裹金面的Janus粒子,由于其結(jié)合了介電和金屬雙重光學(xué)性質(zhì),打破了粒子的結(jié)構(gòu)對(duì)稱性,在光場(chǎng)中受力變得十分復(fù)雜,難以直接估測(cè)在光阱中的運(yùn)動(dòng)形態(tài)。目前對(duì)于捕獲這一類特殊構(gòu)造小球的研究基本處于空白狀態(tài)。本文主要針對(duì)這類介電-金屬材料Janus粒子在多種光場(chǎng)中的運(yùn)動(dòng)形態(tài)展開研究。本文內(nèi)容主要包括五個(gè)方面:第一,基于幾何光學(xué)方法,提出了一套計(jì)算半裹金面的Janus粒子在光場(chǎng)中受力和受力矩的方法。該方法結(jié)合金屬膜理論和動(dòng)量守恒定律,通過計(jì)算光線在Janus粒子的金面和非金面上折射、反射和吸收,從而計(jì)算出Janus粒子在光阱中的受力和受力矩。第二,從實(shí)驗(yàn)上觀察到聚苯乙烯小球在線聚焦光阱中自組裝結(jié)晶過程。其中,光致結(jié)晶過程分為兩種增長(zhǎng)模式,外延式增長(zhǎng)和嵌入式增長(zhǎng)。此外,我們還觀察到膠體從一維到二維結(jié)晶的轉(zhuǎn)變過程。這些觀察有助于深入認(rèn)識(shí)膠體的結(jié)晶過程。第三,通過調(diào)節(jié)聚苯乙烯小球的濃度,控制自組裝后成膜的聚苯乙烯小球陣列的間隙,利用磁控濺射技術(shù)實(shí)現(xiàn)“半月狀”和普通半裹金面的Janus粒子的制備。在實(shí)驗(yàn)中,我們發(fā)現(xiàn)“半月狀”Janus粒子更容易在點(diǎn)聚焦光阱中旋轉(zhuǎn),而普通Janus粒子在點(diǎn)聚焦光阱中趨于穩(wěn)定;Janus粒子的旋轉(zhuǎn)方向和旋轉(zhuǎn)速度可分別通過粒子進(jìn)入光阱的方向以及激光功率來控制。經(jīng)數(shù)值計(jì)算,“半月狀”Janus粒子的穩(wěn)定旋轉(zhuǎn)是主要由粒子的自發(fā)對(duì)稱性的破缺而引起的。第四,首次報(bào)道了Janus粒子在線聚焦光阱中進(jìn)行著罕見的自驅(qū)動(dòng)式循環(huán)往復(fù)運(yùn)動(dòng)�？紤]到點(diǎn)聚焦光阱中單位面積上激光強(qiáng)度很強(qiáng),導(dǎo)致金屬膜強(qiáng)吸收而產(chǎn)生熱效應(yīng),從而對(duì)Janus粒子的運(yùn)動(dòng)有一定影響。為了降低金屬熱效應(yīng)帶來的影響,我們利用柱透鏡生成線聚焦光阱,減少光阱一個(gè)方向上的束縛,降低了單位面積的光場(chǎng)強(qiáng)度。線聚集光阱在聚焦線平面呈現(xiàn)中心強(qiáng)、兩端弱的光強(qiáng)分布,因此沿著聚焦線方向自然產(chǎn)生了一個(gè)指向聚焦線中心的橫向梯度力,并且該梯度力隨著位置的變化而變化。產(chǎn)生循環(huán)往復(fù)運(yùn)動(dòng)的主要原因有兩點(diǎn),一是Janus粒子材料結(jié)構(gòu)的不對(duì)稱性而產(chǎn)生的推動(dòng)力和線聚焦光阱的不對(duì)稱性而提供的橫向梯度力共同作用和相互競(jìng)爭(zhēng);二是由于Janus粒子的自發(fā)對(duì)稱性破缺,粒子在受力為零時(shí)所受光力矩不為零,改變了Janus粒子的取向。這兩個(gè)因素給循環(huán)往復(fù)運(yùn)動(dòng)提供了必要條件。第五,我們觀察到Janus粒子圍繞著環(huán)形光阱做同步轉(zhuǎn)動(dòng)。當(dāng)意識(shí)到Janus粒子在平動(dòng)和轉(zhuǎn)動(dòng)兩個(gè)方面具有強(qiáng)大的耦合能力之后,我們利用錐形透鏡生成環(huán)形光鑷,構(gòu)建在光的環(huán)形路徑上完全一致的光強(qiáng)分布,一是降低光的聚焦強(qiáng)度,從而降低熱效應(yīng);二是提供曲率一致的環(huán)形路徑。如此一來,便可以減少外在因素的影響,專注研究Janus粒子在光場(chǎng)中平動(dòng)和轉(zhuǎn)動(dòng)的耦合。實(shí)驗(yàn)表明Janus粒子圍繞著環(huán)形光阱做同步轉(zhuǎn)動(dòng),如同太空中月亮圍繞著地球運(yùn)動(dòng),自轉(zhuǎn)周期等于公轉(zhuǎn)周期。這意味著Janus粒子在環(huán)形光阱中不僅圍繞光阱中心沿著環(huán)形聚焦光阱公轉(zhuǎn),即平動(dòng);同時(shí)圍繞自己的中心軸自轉(zhuǎn),即自轉(zhuǎn)。并且在實(shí)驗(yàn)中觀測(cè)到的Janus粒子公轉(zhuǎn)周期和自轉(zhuǎn)周期基本一致�？偟膩碚f,Janus粒子在點(diǎn)聚焦、線聚焦、環(huán)聚焦光阱中豐富多彩的運(yùn)動(dòng)形態(tài)展示著它們強(qiáng)大的平動(dòng)和轉(zhuǎn)動(dòng)的耦合能力。此外,Janus粒子的取向隨著光場(chǎng)分布的變化進(jìn)行自動(dòng)的調(diào)整,具有很強(qiáng)的光學(xué)自適應(yīng)性,在未來智能操控微納米顆粒中具有極強(qiáng)的潛力。
[Abstract]:Since the technology of optical tweezers, various laser beams have been used for three-dimensional capture and manipulation of the micro-nano-dielectric particles and the nano-scale metal particles, and the trapped particles are used as a handle to explore the unsolved mysteries of single-cell and single-molecule in the living body. In the history of the early development of the optical tweezers, the commonly captured object is a pure dielectric microsphere and a pure metal nanosphere. Because of its isotropic optical properties, it is usually firmly trapped in the light trap, and it is difficult to observe its rich and colorful motion form in the microworld. and the structure symmetry of the particles is broken due to the combination of the dielectric and the metal dual optical properties, the stress in the optical field becomes very complex, it is difficult to directly estimate the motion morphology in the light trap. At present, the research on the capture of this kind of special construction ball is in the blank state. In this paper, the movement of Janus particles of this kind of dielectric-metallic material in a variety of optical fields is studied. This paper mainly includes five aspects: first, based on the geometric optics method, a set of methods for calculating the force and moment of Janus particles in a half-covered gold surface in the optical field is proposed. The method combines the theory of metal film and the law of momentum conservation, and calculates the force and moment of Janus particles in the light trap by calculating the refraction, reflection and absorption of light on the gold surface and the non-gold surface of the Janus particle. Secondly, the self-assembly and crystallization process of polystyrene beads on-line focused optical trap was observed. The photo-induced crystallization process is divided into two growth modes, epitaxial growth and embedded growth. In addition, we also observed the transformation of the colloid from one-dimensional to two-dimensional. These observations contribute to the in-depth understanding of the crystallization process of the colloid. and thirdly, by adjusting the concentration of the polystyrene beads, controlling the gap of the film-forming polystyrene ball array after assembly, and utilizing the magnetron sputtering technology to realize the preparation of the Janus particles of the 鈥渟emilunar鈥，

本文編號(hào)：2324616