Nano scale devices for plasmonic nanolithography and rapid sensing of bacteria
MetadataShow full item record
This dissertation contains two different research topics. One is a ‘Nano Scale Device for Plasmonic Nanolithography – Optical Antenna’ and the other is a ‘Nano Scale Device for Rapid Sensing of Bacteria – SEPTIC’. Since these two different research topics have little analogy to each other, they were divided into different chapters throughout the whole dissertation. The ‘Optical Antenna’ and ‘Nanowell / Microwell / ISFET Sensor’ represent the device names of each topic ‘Plasmonic Nanolithography’ and ‘Rapid Sensing of Bacteria’, respectively. For plasmonic nanolithography, we demonstrated a novel photonic device - Optical Antenna (OA) - that works as a nano scale object lens. It consists of a number of sub-wavelength features in a metal film coated on a quartz substrate. The device focuses the incident light to form a narrow beam in the near-field and even far-field region. The narrow beam lasts for up to several wavelengths before it diverges. We demonstrated that the OA was able to focus a subwavelength spot with a working distance (also the focal length) of several µm, theoretically and experimentally. The highest imaging resolution (90-nm spots) is more than a 100% improvement of the diffraction limit (FWHM = 210 nm) in conventional optics. A model and 3D electromagnetic simulation results were also studied. Given its small footprint and subwavelength resolution, the PL holds great promise in direct-writing and scanning microscopy. Collaborative work demonstrated a Nanowell (or Microwell) device which enables a rapid and specific detection of bacteria using nano (or micro) scale probe to monitor the electric field fluctuations caused by ion leakage from the bacteria. When a bacteriophage infects a bacterium and injects its DNA into the host cell, a massive and transitory ion efflux from the host cell occurs. SEPTIC (SEnsing of Phage-Triggered Ion Cascade) technology developed by collaboration uses a nanowell device to detect the nano-scale electric field fluctuations caused by this ion efflux. The SEPTIC provides fast (within several minutes), effective (living cell only), phage specific (simple and less malfunction), cheap, compact and robust method for bacteria sensing. We fabricated a number of devices, including ‘Nanowell’, ‘Microwell’, and ‘ISFET (Ion Selective Field Effect Transistor)’, which detect bacteria-phage reactions in frequency domain and time domain. In the frequency domain, detected noise spectrum is characterized by β f / 1 . The positive reaction showed much higher 1 ≅ β than that of background noise or negative reaction ( 0 ≅ β ). For the time domain, we observed abnormal pulses (> σ 8 ) lasting 0.1 ~ 0.3 s which match the duration of ion flux reported by prior literatures. And the ISFET showed the phage-infection-triggered pulse in the form of the deviated drain current. Given the size of nanowell (or microwell, ISFET) and the simplified detection electronics, the cost of bacteria sensing is significantly reduced and the robustness is well improved, indicating very promising applications in clinical diagnosis and bio-defense.
Seo, Sungkyu (2007). Nano scale devices for plasmonic nanolithography and rapid sensing of bacteria. Doctoral dissertation, Texas A&M University. Available electronically from