There is a growing interest in making sensors, optoelectronic and electronic devices with nanomaterials. Carbon
nanotubes (CNTs) are unique materials due to their excellent electrical, mechanical and thermal properties, and also
have good chemical stability. Single-walled carbon nanotubes (SWNTs) are formed by one atomic layer and have an
extended π-bonding configuration. The conductivity of SWNTs is sensitive to trace amount of molecules or ions
attached onto their surfaces. CNTs have exceptionally high sensitivity and fast response and were utilized in
numerous chemical and biological sensing applications for environmental monitoring. One of the present problems
with SWNT sensors is their nonselective response to many analytes. SWNTs networks were assembled onto the
microelectrodes by a low temperature, low cost Dielectrophoretic (DEP) assembly process. SsDNA of different
sequences were used to functionalize the nanotubes and improved their response to the gas vapors dramatically. To
reduce the undesirable response of SWNTs to interfering analytes, a wireless nanosensor array with six channels
each functionalized with different molecules were developed to measure the resistances of six SWNT sensors
simultaneously during exposure to gases. The responses of different DNA decorated SWNTs and bare SWNTs to
toxic organics were measured simultaneously and displayed by a GUI interface. Development of this wireless sensor
array enabled real-time gas monitoring with various DNA functionalized SWNTs from a distance.
Single-walled carbon nanotubes (SWNTs) with their unique electrical properties and large surface area are
remarkable materials for detecting low concentration of toxic and hazardous chemicals (both from the gaseous and
liquid phases). Ionic adsorbates in water will attach on to SWNTs and drastically alter their electrical properties.
Several SWNTs based pH and chemical sensors have been demonstrated. However, most of them require external
components to test and analyze the response of SWNTs to ions inside the liquid samples. Here, we report a water
quality monitoring sensor composed of SWNTs integrated inside microfluidic channels and on-chip testing
components with a wireless transmission board. To detect multiple analytes in water requires the functionalization
of SWNTs with different chemistries. In addition, microfluidic channels are used to guide liquid samples to
individual nanotube sensors in an efficient manner. Furthermore, the microfluidic system enables sample mixing and
separation before testing. To realize the nanosensors, first microelectrodes were fabricated on an oxidized silicon
substrate. Next, PDMS micro channels were fabricated and bonded on the substrate. These channels can be
incorporated with a microfluidic system which can be designed to manipulate different analytes for specific
molecule detection. Low temperature, solution based Dielectrophoretic (DEP) assembly was conducted inside this
microfluidic system which successfully bridged SWNTs between the microelectrodes. The SWNTs sensors were
next characterized with different pH buffer solutions. The resistance of SWNTs had a linearly increase as the pH
values ranged from 5 to 8. The nanosensor incorporated within the microfluidic system is a versatile platform and
can be utilized to detect numerous water pollutants, including toxic organics and microorganisms down to low
concentrations. On-chip processing and wireless transmission enables the realization of a full autonomous system
for real time monitoring of water quality.
Single-walled carbon nanotubes (SWNTs) with their large surface area, high aspect ratio are one of the novel
materials which have numerous attractive features amenable for high sensitivity sensors. Several nanotube based
sensors including, gas, chemical and biosensors have been demonstrated. Moreover, most of these sensors require
off chip components to detect the variations in the signals making them complicated and hard to commercialize.
Here we present a novel complementary metal oxide semiconductor (CMOS) integrated carbon nanotube sensors for
portable high sensitivity chemical sensing applications. Multiple zincation steps have been developed to ascertain
proper electrical connectivity between the carbon nanotubes and the foundry made CMOS circuitry. The SWNTs
have been integrated onto (CMOS) circuitry as the feedback resistor of a Miller compensated operational amplifier
utilizing low temperature Dielectrophoretic (DEP) assembly process which has been tailored to be compatible with
the post-CMOS integration at the die level. Building nanotube sensors directly on commercial CMOS circuitry
allows single chip solutions eliminating the need for long parasitic lines and numerous wire bonds. The carbon
nanotube sensors realized on CMOS circuitry show strong response to various vapors including Dimethyl
methylphosphonate and Dinitrotoluene. The remarkable set of attributes of the SWNTs realized on CMOS electronic
chips provides an attractive platform for high sensitivity portable nanotube based bio and chemical sensors.
Anodized aluminum oxide (AAO) membranes are fabricated under different anodization potentials in dilute sulfuric
acid. Here we report the growth of AAO under 10, 15, 20, and 25V. These AAO membranes consist of nanopores with
pore-to-pore distance from 35 to 69 nm. When AAO membranes are kept thin (less than ~500 nm), together with the
unreacted aluminum substrate, interference colors are observed. The inference color of the membrane is changed by its
thickness and the pore-to-pore distance, which is controlled by the anodization time and voltage, respectively. By using
thin film interference model to analyze the UV-Vis reflectance spectra, we can extract the thickness of the membrane.
Thus the linear growth of AAO membrane in sulfuric acid with time during the first 15 minutes is validated. Coating
poly (styrene sulfonate) (PSS) sodium salt and poly (allylamine hydrochloride) (PAH) layer by layer over the surface of
AAO membrane consistently shifts the interference colors. The red shift of the UV-Vis reflectance spectrum is correlated
to the number of layers. This color change due to molecular attachment and increasing thickness is a promising method
for chemical sensing.