Design, Fabrication, Testing of CNT Based ISFET and Characterization of Nano/Bio Materials Using AFM

A combination of Carbon Nanotubes (CNTs) and Ion Selective Field Effect Transistor (ISFET) is designed and experimentally verified in order to develop the next generation ion concentration sensing system. Micro Electro-Mechanical System (MEMS) fabrication techniques, such as photolithography, diffusion, evaporation, lift-off, packaging, etc., are required in the fabrication of the CNT-ISFET structure on p-type silicon wafers. In addition, Atomic Force Microscopy (AFM) based surface nanomachining is investigated and used for creating nanochannels on silicon surfaces. Since AFM based nanomanipulation and nanomachining is highly controllable, nanochannels are precisely scratched in the area between the source and drain of the FET where the inversion layer is after the ISFET is activated. Thus, a bundle of CNTs are able to be aligned inside a single nanochannel by Dielectrophoresis (DEP) and the drain current is improved greatly due to CNTs` remarkable and unique electrical properties, for example, high current carrying capacity. ISFET structures with or without CNTs are fabricated and tested with different pH solutions. Besides the CNT-ISFET pH sensing system, this dissertation also presents novel AFM-based nanotechnology for learning the properties of chemical or biomedical samples in micro or nano level. Dimensional and mechanical property behaviors of Vertically Aligned Carbon Nanofibers (VACNFs) are studied after temperature and humidity treatment using AFM. Furthermore, mechanical property testing of biomedical samples, such as microbubbles and engineered soft tissues, using AFM based nanoindentation is introduced, and the methodology is of great directional value in the area

Experimentally validated 3D MD model for AFM-based tip-based nanomanufacturing

In order to control AFM-based TBN to produce precise nano-geometry efficiently, there is a need to conduct a more focused study of the effects of different parameters, such as feed, speed, and depth of cut on the process performance and outcome. This is achieved by experimentally validating a MD simulation model of nanomachining, and using it to conduct parametric studies to guide AFM-based TBN. A 3D MD model with a larger domain size was developed and used to gain a unique insight into the nanoindentation and nanoscratching processes such as the effect of tip speed (e.g. effect of tip speed on indentation force above 10 nm of indentation depth). The model also supported a more comprehensive parametric study (than other published work) in terms of number of parameters and ranges of values investigated, as well as a more cost effective design of experiments. The model was also used to predict material properties at the nanoscale (e.g. hardness of gold predicted within 6% error). On the other hand, a comprehensive experimental parametric study was conducted to produce a database that is used to select proper machining conditions for guiding the fabrication of nanochannels (e.g. scratch rate = 0.996 Hz, trigger threshold = 1 V, for achieving a nanochannel depth = 50 nm for the case of gold device). Similar trends for the variation of indentation force with depth of cut, pattern of the material pile-up around the indentation mark or scratched groove were found. The parametric studies conducted using both MD model simulations and AFM experiments showed the following: Normal forces for both nanoindentation and nanoscratching increase as the depth of cut increases. The indentation depth increases with tip speed, but the depth of scratch decrease with increasing tip speed. The width and depth of scratched groove also depend on the scratch angle. The recommended scratch angle is at 90°. The surface roughness increases with step over, especially when the step over is larger than the tip radius. The depth of cut also increases as the step over decreases. Additional study is conducted using the MD model to understand the effect of crystal structure and defects in material when subjected to a stress. Several types of defects, including vacancies and Shockley partial dislocation loops, can be observed during the MD simulation for the case of gold, copper and aluminum. Finally, AFM-based TBN is used with photolithography to fabricate a nano-fluidic device for medical application. In fact, the photolithography process is used to create microchannels on top of a silicon wafer, and AFM-based TBN is applied to fabricate nanochannels between the microchannels that connect to the reservoirs. Fluid flow test was conducted on the devices to ensure that the nanochannel was open and the bonding sealed

Voltage gated inter-cation selective ion channels from graphene nanopores

With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we demonstrate that nanopores introduced into graphene membranes, as large as 50 nm in diameter, exhibit inter-cation selectivity with a ~20x preference for K+ over divalent cations and can be modulated by an applied gate voltage. Liquid atomic force microscopy of the graphene devices reveals surface nanobubbles near the pore to be responsible for the observed selective behavior. Molecular dynamics simulations indicate that translocation of ions across the pore likely occurs via a thin water layer at the edge of the pore and the nanobubble. Our results demonstrate a significant improvement in the inter-cation selectivity displayed by a solid-state nanopore device and by utilizing the pores in a de-wetted state, offers an approach to fabricating selective graphene membranes that does not rely on the fabrication of sub-nm pores

Progress in Nanoporous Templates: Beyond Anodic Aluminum Oxide and Towards Functional Complex Materials

Successful synthesis of ordered porous, multi-component complex materials requires a series of coordinated processes, typically including fabrication of a master template, deposition of materials within the pores to form a negative structure, and a third deposition or etching process to create the final, functional template. Translating the utility and the simplicity of the ordered nanoporous geometry of binary oxide templates to those comprising complex functional oxides used in energy, electronic, and biology applications has been met with numerous critical challenges. This review surveys the current state of commonly used complex material nanoporous template synthesis techniques derived from the base anodic aluminum oxide (AAO) geometry

Radio Frequency Micro/Nano-Fluidic Devices for Microwave Dielectric Property Characterizations

In this dissertation, a number of different topics in microwave dielectric property measurements have been covered by a systematic approach to the goals of development of dielectric spectroscopy and study of its high electric field effects with integrated on-chip microwave microfluidic / nanofluidic devices. A method of parasitic effects cancellation for dielectric property measurement is proposed, analyzed, and experimentally evaluated for microwave characterization of small devices and materials that yield low intensity signals. The method dramatically reduces parasitic effects to uncover the otherwise buried signals. A high-sensitive radio frequency (RF) device is then developed and fabricated to detect small dielectric property changes in microfluidic channel. Sensitivity improvement via on-chip transmission line loss compensation is then analyzed and experimentally demonstrated. Different samples are measured and high sensitivity is achieved compared to conventional transmission-line-based methods. High DC electric field effects on dielectric properties of water are investigated with microwave microfluidic devices. Gold microstrip-line-based devices and highly-doped silicon microstrip-line-based devices are exploited. Initiation process of water breakdown in a small gap is discussed. Electrode surface roughness is examined and its effect on observed water breakdown is investigated. It is believed that electrode surface roughness is one of critical factors for the initiation process of water breakdown in small gap system. Finally, water dielectric property subjected to uniform DC electric field in 260 nm planar microfluidic channels is experimentally studied via silicon microstrip-line-based devices. When applied DC field is as high as up to ~ 1 MV/cm, the water is sustained and no breakdown is occurred. Strong water dielectric saturation effects are observed from measured water dielectric spectroscopy. An on-chip, broadband microwave dielectric spectrometer with integrated transmission line and nanofluidic channels is designed, fabricated and characterized through microwave S-parameter measurements. Heavily-doped Si material is used to build the microstrip line to provide broadband characterization capability. 10 nm deep planar Si nanofluidic channels are fabricated through native oxide etch and wafer bonding process. It is the first effort to build the microstrip line with periodically loaded individual sub-10 nm nanofluidic channels to conduct the broadband high frequency characterization of materials within confined space. The functionality of the device is demonstrated by the measurement of DI water. It behaves well and has great potentials on the study of confinement effects of fluids and molecules. Further work includes development of parasitic signal de-embedding procedures for accurate measurements

Design and Fabrication of Nanofluidic Systems for Biomolecule Characterizations

Nanofluidic channel systems were designed and fabricated by combining MEMS microfabrication with AFM nanolithography. In the fabrication process flow, photolithography was first utilized to pattern microfluidic channels and reservoirs on a 4 Pyrex substrate. Subsequently, atomic force microscopy (AFM) based nanolithography was used to mechanically fabricate nanochannels to connect the microreservoirs which formed the inlet and outlet of the nanofluidic system. A Tap190 Diamond-Like Carbon (DLC) AFM tip with a force constant of 48 N/m and a radius of less than 15 nm was used as the nanolithography tool. The resultant nanochannel ranges from 20 to 80 µm in length and 10 to 100 nm in depth. After AFM, the Pyrex micro- and nanochannels were sealed off by a matching silicon capping piece using anodic bonding. Fluidic connectors are then attached to the inlet and outlet openings to complete the fabrication process. The relationship between the nanolithography parameters of the AFM and the resultant nanochannel dimensions was investigated in detail. A mostly linear trend was obtained between the AFM tip force and the nanochannel depth for a tip speed of 1 µm/s. This result was consistent with established nanotribological models and similar studies on silicon substrates. The relationship between the number of repeated scratches and the nanochannel depth was also investigated. The results indicated that the nanochannel depth increased with the number of scratches. A depth of about 20 nm was typically achieved with 25 scratches at a tip force of 25 µN. The width of the nanochannel also increased with the number of scratches. A typical nanochannel width of 120 nm was achieved for 25 scratches at 10 µN. Two different flow tests were conducted using the nanochannel system. In the first test, a fluorescent fluid, Fluorescein, was pumped through the nanochannel to demonstrate channel patency. To achieve this, a sequential wetting procedure was executed to modify the surface chemistry of the nanochannel system. Fluorescence microscopy confirmed the passage of fluid through a 40 µm long and 45nm deep channel. In the second test, negatively charged nanobeads, carboxylate-modified FluoSpheres, were translocated through the nanochannel using an externally supplied DC electric field

Angstrofluidics:walking to the limit

Angstrom-scale fluidic channels are ubiquitous in nature, and play an important role in regulating cellular traffic, signaling, and responding to stimuli. Synthetic channels are now a reality with the emergence of several cutting-edge bottom-up and top-down fabrication methods. In particular, the use of atomically thin two dimensional (2D) materials and nanotubes as components to build fluidic conduits has pushed the limits of fabrication to the Angstrom-scale. Here, we provide an overview of the recent developments in the fabrication methods for nano- and angstrofluidic channels while categorizing them on the basis of dimensionality (0D pores, 1D tubes, 2D slits), along with the latest advances in measurement techniques. We discuss the ionic transport governed by various stimuli in these channels and draw comparison of ionic mobility, streaming and osmotic power, with varying pore sizes across all the dimensionalities. Towards the end of the review, we highlight the unique future opportunities in the development of smart ionic devices.Comment: Keywords: Angstrofluidics, nanofluidics, confinement, ion transport, 2D materials, molecular transport 6 figures, review articl

Implantable Nanofluidic Membrane and Smart Electronic System for Drug Release Control

L'abstract è presente nell'allegato / the abstract is in the attachmen