桿狀病毒的偶極模態分析與其微波共振吸收量測

Abstract

病毒是一種廣為人知的微生物，它只能在宿主的細胞系統進行自我複製，無法獨立生長與複製。根據病毒的幾何形狀，大多數病毒可以簡單分為球狀病毒和桿狀病毒兩類。一般而言，不少種球狀病毒會對人體有感染性，然而桿狀病毒幾乎不會，大多數桿狀病毒主要會感染無脊椎動物(如:昆蟲和蝦子)、植物或是細菌。 近期有人開始研究病毒的微波共振吸收特性，其原理是透過微波和侷限的有聲振動進行偶極性耦合進而發生共振吸收。如果將一個病毒粒視為一個自由且同質性的奈米粒子，而此病毒的微波共振吸收頻率會與其幾何形狀、質量密度以及彈性特性有關。目前為止，只有球狀病毒的微波共振吸收已被發現，且其共振頻率和偶極模態的頻率吻合，而桿狀病毒還未被發現具有微波共振吸收的特性。 在此論文中，我們是將一個桿狀病毒看作為自由同質性的奈米柱，而此奈米柱具有和桿狀病毒相同的大小和物理特性，再來根據不同電荷分布情況，分析每一個模態在振動過程中偶極矩的變化量，最後得出桿狀病毒會在哪些振動模態有比較強的微波共振吸收。為了讓理論模型更完整以及更吻合各種桿狀病毒，我們除了建立基本的圓柱模型之外，也建立了膠囊模型，再利用有限元素分析法來求出它們的振動模態。此外，我們主要用共平面波導結合微流道和網路分析儀作為量測病毒的實驗系統，並且用此系統成功地量測出蝦白點病毒的微波共振吸收，其共振吸收頻率也落在理論的分析結果範圍內。 從我們的研究分析可以推測桿狀病毒的微波共振吸收會發生在哪些振動模態，此外我們也建立了一個量測病毒微波共振吸收特性的實驗系統，這些研究對於迅速又準確的桿狀病毒偵測發展是重要的一步，同時也可以應用於分析桿狀病毒的物理特性。

Virus is a well-known microorganism and the infectious agent that replicates only in the living cells of other organisms. Based on the geometric structure of viruses, most viruses can be simply classified as spherical (or icosahedral) viruses and rod-shaped viruses. In general, most spherical viruses are infectious for human being while rod-shaped viruses are almost not. Most rod-shaped viruses can infect invertebrates (such as insects and shrimps), plants or bacteria. Recently, the microwave resonant absorption (MRA) of viruses has been researched. This MRA mechanism is through dipolar coupling to confined acoustic vibrations. By treating one virion as a free homogeneous nanoparticle, the unique geometrical and mechanical properties of viruses can be reflected by the MRA frequencies. So far, only the MRA of spherical viruses have been discovered, and the MRA frequencies agree well with that of dipolar vibration modes. However, the MRA characteristic of rod-shaped viruses hasn’t been found. In this thesis, we treat a rod-shaped virus as a free homogenous nanorod with the rod-shaped virus’s geometrical and elastic properties and identify the vibration modes of a nanorod which can cause the stronger MRA in different charge distribution situations through analyzing the dipolar modulations of each vibration mode. We analyzed not only the cylinder model but also the capsule model, which let our theoretical model more complete and match the rod-shape virus better. The vibration modes are simulated by finite element method in both models. Moreover, we successfully discover the MRA of white spot syndrome virus (WSSV), which is one of rod-shaped viruses, by our MRA experiment system. This system mainly utilizes a coplanar waveguide combined with a microfluidic channel and a vector network analyzer. We also find that the MRA frequencies of WSSV closely agree with our analysis results. From our study results, we propose a theory to know that the MRA of rod-shaped viruses should happen in which vibration modes and also develop an MRA system to measure the viruses. Our study is an important step to achieve rapid and sensitive detection of rod-shaped viruses and a method to know the physical properties of rod-shaped viruses.