網狀奈米碳管之電晶體研製及其在生物粒子檢測之應用


指導教授 : 黃榮堂  研究生 : 林逸青  機電整合研究所 94年


摘要

  奈米科技指的是研究、操縱、製造、使用大小範圍小於100nm的物質之技術。目前將奈米科技應用於生物感測器是一項重要的研究方向,其優點是可以增加生物感測器的靈敏度。在本研究中,我們以奈米碳管取代了傳統的場效電晶體通道,若將奈米碳管連接固定於電晶體源極(Source)及汲極(Drain)之間,由於奈米碳管易於與蛋白質或核酸產生連結,在奈米碳管上修飾不同生化分子,當粒子吸附於碳管表面上將造成碳管電性之改變或是在接附上碳管上產生電子的轉移,藉以放大或檢測訊號的改變,由於使用單壁半導體型奈米碳管當作通道,所以將對碳管表面電荷變化十分靈敏,預期可架構成一個高靈敏度且具有專一性之場效電晶體生化感測器。
  有鑒於傳統之碳管高溫成長方式容易影響破壞與奈米碳管結合之具有處理邏輯運算的電子元件,本論文中提供了一種用一種以低溫的方式將奈米碳管有效率、有規模地附著固定於電極之方法,利用介電泳(Dielectrophoresis, DEP)力操控奈米碳管至金屬層電極固定好。爲使我們能偵測之微米等級的生物粒子,在跨接兩電極間的碳管以連接成一網狀形式為目標,以符合尺度上的需求。
  如前述當單壁奈米碳管 (m, n)值為m – n ≠ 3 × integer時呈半導體特性,其能隙分佈從~2 eV到小於0.5eV;此時奈米碳管元件特性將與閘極偏壓(bias)強烈相關,因此可應用此材料構築奈米電子系統中的各式單元,如場效電晶體。本論文以上述方法製作出一典型的奈米碳管場效電晶體,表面功能化則將碳管表面以聚乙烯亞胺(polyethyleneimine, PEI)及聚乙二醇(polyethyleneglycol, PEG)兩種高分子加以改質,PEI主要提供胺基官能基,以接續固定抗體,並利用抗體及抗原間極強的特異親和性作用力來感測生物粒子之訊號,PEG則用以避免蛋白質的非特異性吸附,抗體和抗原結合後改變奈米碳管表面的電荷分佈,進而調控碳管通道的導電度。在本論文中以沙門氏菌當做測試之檢體,初步的證實經過改質之奈米碳管場效電晶體可有效地偵測到極微量沙門氏菌的反應。
 

關鍵詞:微機電(MEMS)技術、奈米碳管場效電晶體、介電泳、生物感測器

ABSTRACT

 Nano-technology includes studying, manipulating, manufacturing and using the materials with size of particles smaller than 100nm. Presently, it is in great demand to apply nano-technology in bio-sensor with an advantage of improving the sensitivity. In this study, we use carbon nanotubes (CNTs) to take the place of channels of traditional transistors by settling CNTs between the source and drain of transistors. CNTs are easy to combine with protein or nucleotide. When particles are adsorbed on the surface of CNTs, the electric properties of CNTs are changed and the electrons produced on CNTs are transferred after the surface modification by different biochemical molecule. That is, it can be used to detect changes of signals. Because we use the single-wall CNTs as channels, it is very sensitive to the change of charges on the surface of CNTs. Therefore, it can be anticipated to form a novel bio-sensor with both high sensitivity and specific property.
 Traditionally, the high temperature of CNTs growth caused damages to the logical electronic devices hinder the combining with CNTs. In this thesis, we compose a novel way of settling a CNT on electrodes efficiently at low temperature, and use DEP force to make sure CNTs be well touched on electrodes. In order to detect bio-particles with size of micro-meter, the connection between CNT and two electrodes should be like a meshed shape to meet the desired specification.
 As to the previous description, while (m, n) value of SWCNTs meets the condition of m – n ≠ 3 × integer, it behaves like semiconductors with a bandgap from -2eV to 0.5eV. At this status, the properties of CNT-devices relate to the bias of gate terminal tremendously and can be used to construct units of nano-electronic system, such as field effect transistors (FETs). In this thesis, a typical CNTFET is fabricated and the surface of CNT is modified by polyethyleneimine (PEI) and polyethyleneglycol (PEG). PEI primarily provide amine group to connect antibody. Use the specific affinity between antibody and antigen to detect signals of bio-particles. PEG prevents protein itself from none-specific adsorption. The combination of antibody and antigen changes charge distribution on the surface of CNT, and which can be used to control the conductivity of channel in CNT. In this thesis, we chose Salmonella as sample, and the preliminary result confirms that the modified network CNTFETs can have signals responses to very rare Salmonellas.

Key Words: MEMS, carbon nanotubes field effect transistor, CNTs dielectrophoresis, DEP, Biosensor.