- 學位論文
量測與模擬奈米粒子在圓錐形孔洞的傳輸
Measurement and modeling of nanoparticle transport in conical-shaped nanopores
摘要
隨著醫學的進步與發展，各式各樣的生物粒子被科學家發現與應用。而要利用這些生物粒子作為研究上的材料，我們需要適當的工具量測它的濃度、大小等參數以便於我們在研究上能系統化的歸類並做後續的分析與處理。奈米等級大小的生物粒子，如病毒、囊泡、核內體都是現今重要的研究對象，其生化反應能幫助我們在醫學方面的進展。現今用來量測奈米等級大小的儀器還在持續發展階段，需要去探討其準確度和精密度以確保量測資料的正確性。 可調式阻性脈衝感測器(Tunable Resistive Pulse Sensing)其原理來自於庫特計數器(Coulter Counter)，是一種在圓錐形奈米孔洞兩端加入電解質通電後，當有奈米大小的粒子通過時，因其阻抗和電解質不同，故能發現電流的變化，而此電流變化的大小和粒子體積大小成正比，所以此裝置能根據電流變化測得粒子之大小。在本研究之中，我們探討此技術在量測非圓形粒子時所造成之誤差，以及研究因粒子表面帶電而產生的電流上升波型(positive peak)，此波型有機會作為量測粒子表面電荷密度之現象。 本研究利用有限元素分析法(Finite Element Method)探討奈米粒子可能會在可調式阻性脈衝感應器造成誤差之參數，包含行走軌跡、傾角、粒子長寬比等，及模擬圓形粒子和長條形粒子通過圓錐形奈米孔洞的電流大小差異。由模擬結果得知，粒子行走路徑越偏離中心產生的電流變化幅度越大；長條形粒子的傾角越大，造成之電流變化幅度越大；而同體積長條形粒子之長寬比越大，造成之電流變化幅度越大。在Positive peak研究方面，我們利用有限元素分析法，探討電壓、壓力、粒徑、濃度以及粒子表面電荷等參數大小對Positive peak有何影響。其中要能產生此現象關鍵的點在於離子濃度極化的產生。當奈米通道和奈米粒子表面帶有電荷時，會因為電壓方向不同，兩端聚集不同濃度的離子，當奈米粒子通過流道時，會因為離子濃度的不同，造成電流額外的變化，而Positive peak的產生就是因為奈米粒子帶有較高濃度的離子使得電流上升的現象。
並列摘要
As the improvement of medication, kinds of particles are studied and applied in biology and medication. For example, vesicles, viruses and endosomes are particles in nanoscale, currently under studied for the application of medication. For well use of these nanoparticle, we need to measure the size, concentration and surface properties to control the parameters systematically. Proper tools to measure these parameters for nanoscale particle are not perfect enough now, so the accuracy and precision need more improvement. Tunable resistive pulse sensing, based on the coulter counter, is a non-optical sensing technique to measure the size and concentration of nanoparticles. A voltage drop is applied on the both reservoirs connecting with a conical-shaped nanopores full of electrolytes. When a particle travels through the nanopore, a current decrease can be observed since the difference of the resistance between particle and electrolytes. The magnitude of current decrease is related to the volume of particle. Hence, this technique can measure the size of nanoparticle. In this thesis, we study the magnitude of current in the case of non-spherical particle traveling through the nanopore, and the parameters affecting positive peaks. The formation of positive peaks is related to the surface charge of the particle, so there is a potential for measuring the surface charge via positive peaks. In this thesis, we use finite element analysis to investigate paramters which can affect the magnitude of current drop when a particle travels through the nanopore, including path, tilt angle and the ratio of length and width of cylindrical particle. According to the simulation results, we find the magnitude of current change increases with the distance from particle and central line of nanopore increases. The more the tilt angle of the cylindrical particle is, the more the magnitude of current change increases. The more the ratio of length and width of cylindrical particles with same volume, the more the magnitude of current change increases. In the study of positive peaks, we simulated parameters which affect the magnitude of positive peak, including electric potential, pressure drop, concentration of electrolytes, size of particles, and surface charge density of particles. The major cause of the formation of positive peak is the phenomenon called ionic concentration polarization. The surface charges on the particles and nanopores induce the redistribution of ionic concentration near their surfaces which is related to the direction of voltage drop in the system and surface charges. In the case of positive peak, the ionic concentration in the nanopore is higher because the charged particles carry more ions into the nanpore. The magnitude of positive peaks are related to the surface charge on the particles.