藉由波導耦合之金領結結構捕捉奈米粒子

Abstract

我們提出一個以波導偶合激發侷域化表面電漿共振之粒子捕捉系統，此系統具有尺度小以及容易整合於晶片之優點，包含以金為材料的領結結構以及氮化矽波導。由模擬結果預測，領結結構的間隙處具有集中且增強的場分布，可產生強大的光學鉗制力以捕捉微觀尺度的物體。我們發現具5奈米間隙領結結構在1.55微米波長激發下能對20奈米聚苯乙烯粒子產生高達1389pN/W的光學鉗制力。在實驗中為了直接觀測，我們以1微米的聚苯乙烯粒子驗證此系統的粒子捕捉能力，觀測到此粒子沿波導移動最後被領結結構捕捉的完整現象，並於關閉耦合光源後觀測到粒子被釋放並漂離的現象。未來將此捕捉系統與其他感測分析系統一同整合於晶片上將能實現生物晶片的目標。

We propose a particle manipulation system by using localized surface plasma resonance excited by a coupling waveguide. The system, featured with advantages such as small footprint and easily being integrated in a chip, is composed of gold bowtie and silicon nitride waveguide. The simulation shows highly concentrated and enhanced field in gap of the bowtie where strong optical trapping force will be established and will be able to trap microscopic particles. We find a bowtie with 5 nm gap at the tips can provide 1389 pN/W force for trapping 20 nm polystyrene particle under excitation at 1.55 μm wavelength. For direct observation in experiment, we use 1 μm polystyrene particle to verify trapping ability of the system. We see the particle transported along the waveguide and finally being trapped stably by the bowtie. We also see release of the particle which swims away after the excitation light source is turned off. In the future, this system can be integrated with other sensing and analyzing systems to realize lab on a chip.