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Description:
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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
1 /f[beta] . The positive reaction showed much higher [beta] =̃1 than that of background noise or
negative reaction ( [beta] =̃0 ) . For the time domain , we observed abnormal pulses ( > 8[omega] ) 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 . |