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

Physiochemical and Nanomanipulation Studies of Carbon Nanomaterials

Carbon nanomaterials are, without a doubt, one of man\u27s wonder creations. Though these nanomaterials are a very recent trend, extraordinary electromechanical properties and the light weightiness of these nanomaterials attracted the attention of researchers. Although vast research has been done since the start of the US nanotechnology initiative, much effort was in the area of synthesis and characterization of the nanomaterials. However, most of the traditional macroscopic material\u27s theories fail at the nanoscale level, and since the material properties are dependent on size and structure at nanoscale level, the behavior of the carbon nanomaterials in different environments needs attention. High tensile strength and high tensile modulus with low weight make these nanomaterials ideal for light weighted structures. Thus, many space organizations like NASA are conducting research on these exciting nanomaterials. Hence, dimensional changes of carbon nanofibers in the ambient and subzero temperature ranges was quantified and statistically analyzed. Mechanical properties of the carbon nanofibers both at room temperature and in subzero temperature range was measured using AFM based nanoindentation. Inability to control the orientation of the nanomaterials and lack of material integration to substrate were the primary causes for selecting synthesis over deposition even though the former is a cumbersome process. The challenge of nanomaterials integration to substrates can be mitigated by synthesis of nanocomposites, which are hybrid materials with enhanced electromechanical properties and better substrate integration, and the challenge of orientation can be mitigated by nanopatterning i.e., creating the channels using AFM based picolithography. These methods were demonstrated in this thesis

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Graphene inspired sensing devices

Graphene’s exciting characteristics such as high mechanical strength, tuneable electrical prop- erties, high thermal conductivity, elasticity, large surface-to-volume ratio, make it unique and attractive for a plethora of applications including gas and liquid sensing. Adsorption, the phys- ical bonding of molecules on solid surfaces, has huge impact on the electronic properties of graphene. We use this to develop gas sensing devices with faster response time by suspending graphene over large area (cm^2) on silicon nanowire arrays (SiNWAs). These are fabricated by two-step metal-assisted chemical etching (MACE) and using a home-developed polymer-assisted graphene transfer (PAGT) process. The advantage of suspending graphene is the removal of diffusion-limited access to the adsorption sites at the interface between graphene and its support. By modifying the Langmuir adsorption model and fitting the experimental response curves, we find faster response times for both ammonia and acetone vapours. The use of suspended graphene improved the overall response, based on speed and amplitude of response, by up to 750% on average. This device could find applications in biomedical breath analysis for diseases such lung cancer, asthma, kidney failure and more. Taking advantage of the mechanical strength of graphene and using the developed PAGT process, we transfer it on commercial (CMOS) Ion-Sensitive Field-Effect Transistor (ISFET) arrays. The deposition of graphene on the top sensing layer reduces drift that results from the surface modification during exposure to electrolyte while improving the overall performance by up to about 10^13 % and indicates that the ISFET can operate with metallic sensing membrane and not only with insulating materials as confirmed by depositing Au on the gate surface. Post- processing of the ISFET top surface by reactive ion plasma etching, proved that the physical location of trapped charge lies within the device structure. The process improved its overall performance by about 105 %. The post-processing of the ISFET could be applied for sensor performance in any of its applications including pH sensing for DNA sequencing and glucose monitoring.Open Acces

The Study of Carbon Nanotube based Chemi-resistive Portable Biosensors used for the Detection of Bacteria

The successful fabrication and characterization of a portable, disposable single walled carbon nanotube biosensor used for the detection of bacteria was demonstrated by this work. The Si/SiO2 based SWNT growth using chemical vapor deposition techniques successfully developed ultra sensitive thin single walled carbon nanotubes. The SWNTs were transferred to a portable disposable platform, to demonstrate the commercial potential of a SWNT biosensor that is capable of sensing bacteria. The platform was developed to understand the effects of pH sensing, followed by bacteria sensing. The dominant mechanism of sensing for these devices with respect to pH sensing is chemical doping however the sensing mechanism for bacteria detection is undetermined. Using electrochemical impedance techniques to deeply understand and investigate the electrochemical changes to the surface of the SWNT sensors, the resistance change for pH sensing and bacteria sensing was concluded. With an increase in pH levels, the total resistance of the SWNT sensor also increases. The limit of detection for bacteria sensing with this platform was 105 cfu/mL. It was determined that the charge transfer resistance of the SWNT increases with an antibody surface immobilization and then further increases with the addition of bacteria binding to antibody. From bare electrode to antibody and then bacteria, the charge transfer resistances were 774Ω, 1025Ω, and 1229Ω, respectively. The double layer capacitance for these sensors indicated a different pattern. Preliminary results for concentrations lower than 105cfu./mL suggests an increase in double layer capacitance with an increase in analyte concentration. Using SWNTs as the transducing element of chemiresistive biosensors allowed for a further understanding of the electrochemical mechanisms of sensing, as well as successfully fabricating a sensitive, real-time, reproducible electrical bacteria-sensing device

Nanostructured Metal Oxide-Based Microfluidic Biosensors for Point-of-Care Diagnostics

The potential research on microfluidic devices for detection of biomolecules has recently intensified due to its application in point-of-care (POC) diagnostics for global health care. Early detection plays an imperative role to determine predisposition to disease (prevention) or the outcome of disease (monitoring and prognosis). There is a significant need for POC diagnostics devices as perceived from biohazard threats, the spread of infectious disease, home testing and monitoring. The POC diagnostics can provide a convenient and immediate response to a patient test sample. The POC diagnostics can be attained via use of transportable, portable, and handheld instruments such as blood glucometer, cholesterol meter etc. and test kits. It includes testing of blood or urine for pathogens, glucose, cholesterol, blood gas, coagulation, biomarkers, hemoglobin, pregnancy etc. Cheaper, smaller, faster, and smarter devices are the main merits of POC diagnostics for detection of various target analytes. A number of clinical biochemical studies such as blood gas, glucose/lactate/cholesterol, nucleic acid sequence analysis, proteins/peptides, combinatorial synthesis, toxicity monitoring, immunoassays, and forensic analysis are also focused areas for developing microfluidic biochips

Silicon Nanowires for Biosensor Applications

Nanostrukturen haben in den letzten Jahrzehnten durch konsequente Förderung wie der im Jahr 2000 gestarteten National Nanotechnology Initiative der USA oder des deutschen Pendants Aktionsplan Nanotechnologie erhebliches Aufsehen, nicht nur in der Wissenschaft, sondern auch in der technischen und wirtschaftlichen Umsetzung erfahren. In Kombination mit biologischen Systemen, deren Funktionalität sich auf der Größenordnung von Nanometern abspielt, finden nanotechnologische Entwicklungen auf dem Gebiet der Medizin ein großes technisches Anwendungsgebiet. Diese Arbeit widmet sich der Untersuchung und technischen Entwicklung von Siliziumnanodrähten als Sensoren für zukünftige medizinische Anwendungen. Im Gegensatz zu Sensoren die auf dotierten Nanodrähten basieren, wurden hier undotierte Nanodrähte untersucht, die mit geringerem Produktionsaufwand auskommen und mittels Schottky-Barrieren als Feldeffekttransistoren nutzbar sind. Deren Eigenschaften wurden im Hinblick auf pH und Biosensorik theoretisch und experimentell untersucht, sowie technisch in ein lab-on-chip sowie ein kompaktes Multiplexer-Messgerät integriert. In einem zweiten, separaten Teil wurden die Eigenschaften undotierter Nanodrähte für die optische Spektroskopie theoretisch modelliert. Die Inhalte beider Teile werden im folgenden kurz zusammengefasst. Um die elektrischen Sensoreigenschaften der Siliziumnanodrähte zu untersuchen, wurden zunächst Computermodelle der Drähte erstellt, mit deren Hilfe der Elektronentransport in flüssiger Umgebung quantenmechanisch modelliert wurde. Die dafür erstellten Modellvorstellungen waren für die sich daran anschließenden experimentellen Untersuchungen des Rauschverhaltens, der pH-Sensitivität sowie der Biosensoreigenschaften sehr vorteilhaft. Mit Hilfe einer neu entwickelten Messmethode konnte der optimale Arbeitspunkt der Sensoren ermittelt werden, sowie die hohe Sensorqualität mittels einer empirischen mathematischen Beschreibung des zu erwartenden Sensorsignals eingeordnet werden. Weiterhin wurden für die Medizintechnik relevante Messungen von Thrombin durchgeführt. Damit ist für den hier beschriebenen Sensortyp ein proof-of-concept für neuartige medizinische Messelemente gelungen. Um die kleinen Abmessungen der Sensoren darüber hinaus technisch nutzbar zu machen, wurden sie in ein lab-on-chip System integriert, in welchem sie als Sensoren für den pH-Wert sowie die ionische Konzentration in Nanoliter-Tropfen verwendet wurden. Desweiteren wurde in Kooperation mit dem Institut für Aufbau- und Verbindungstechnik ein portables Messgerät entwickelt, welches die parallele Messung mehrerer Nanodrahtsensoren ermöglicht. Im zweiten Teil der Arbeit wird eine theoretische Untersuchung zur Eignung von Silizium-Nanodrähten als Messsonden (Probes) für die optische Spektroskopie vorgestellt. Dazu wurde eine Methode entwickelt mittels derer es möglich ist, Raman und Infrarotspektren von Nanostrukturen mittels Molekulardynamik zu berechnen. Die Methode wurde auf undotierte Silizium-Nanodrähte augewendet und zeigt, dass die Oberflächenbeschaffenheit der Drähte die optischen Spektren entscheidend beeinflusst. Damit konnte die Relevanz von Halbeiter-Nanostrukturen auch für Anwendungen in der optischen Spektroskopie gezeigt werden.:I Introduction: Sensing with Nanostructures 1 Introduction 2 Field effect transistors as electronic sensor elements 3 Packaging: Connecting Nano and Macro 4 Nanostructures as transducers in optical spectroscopy II Electronic sensing with Schottky Barrier silicon nanowires 5 Schottky-Barrier silicon nanowire field effect transistors 6 ISFET measurement principles 7 pH and Biosensing with silicon nanowires 8 Thrombin sensing 9 Silicon nanowire FETs in a Lab-on-a-Chip device 10 Multiplexer sensing platform 11 Experimental methods III Simulating optical spectra of silicon nanowires 12 Theoretical fundamentals 13 Computational Methods 14 Results 15 Bibliography 16 AnhangNanostructures have attracted great attention not only in scientific research, but also in engineering applications during the last decades. Especially in combination with biological systems, whose complex function is controlled from nanoscale building blocks, nanotechnological developments find a huge field of applications in the medical sector. This work is dedicated to the functional understanding and technical implementation of silicon nanowires for future medical sensor applications. In contrast to doped silicon nanowire based sensors, this work is focussed on pure, undoped silicon nanowires, which have lower demands on production techniques and use Schottky-barriers as electric field detectors. The pH and biosensing capabilities of such undoped silicon nanowire field effect transistors were investigated theoretically and experimentally and further integrated in a lab-on-a-chip device as well as a small-scale multiplexer measurement device. In a second separate part, the optical sensing properties of undoped silicon nanowires were theoretically modeled. The main contents of both parts are shortly described in the following paragraphs. A multiscale model of silicon nanowire FETs to describe the charge transport in liquid surrounding in a quantum mechanical framework was developed to investigate the sensing properties of the nanowire sensors in general. The model set the basis for the understanding of the subsequent experimental investigations of noise characterization, pH sensitivity and biosensing properties. With the help of a novel gate sweeping measurement method the optimal working point of the sensors was determined and the high sensor quality could be quantified in terms of an empirical mathematical model. The sensor was then used for measurements of medically relevant concentrations of the Thrombin protein, providing a proof-of-concept for medical applications for our newly developed sensor. In order to exploit the small size of our sensors for technical applications we integrated the devices in lab-on-a-chip system with a microfluidic droplet generation module. There they were used to measure the pH and ionic concentration of droplets. Finally a portable multiplex measurement device for silicon nanowire sensors as well as other ion sensitive FETs was developed in cooperation with the IAVT at TU Dresden (Institut für Aufbau- und Verbindungstechnik). The second part of this thesis investigates the usability of silicon nanowires for optical sensor applications from a theoretical point of view. Therefore a method for the extraction of Raman and Infrared spectra from molecular dynamics simulations was developed. The method was applied to undoped silicon nanowires and shows that the surface properties of the nanowires has a significant effect on optical spectra. These results demonstrate the relevance of semiconductor nanostructures for applications in optical spectroscopy.:I Introduction: Sensing with Nanostructures 1 Introduction 2 Field effect transistors as electronic sensor elements 3 Packaging: Connecting Nano and Macro 4 Nanostructures as transducers in optical spectroscopy II Electronic sensing with Schottky Barrier silicon nanowires 5 Schottky-Barrier silicon nanowire field effect transistors 6 ISFET measurement principles 7 pH and Biosensing with silicon nanowires 8 Thrombin sensing 9 Silicon nanowire FETs in a Lab-on-a-Chip device 10 Multiplexer sensing platform 11 Experimental methods III Simulating optical spectra of silicon nanowires 12 Theoretical fundamentals 13 Computational Methods 14 Results 15 Bibliography 16 Anhan

Wearable System with Integrated Passive Microfluidics for Real-Time Electrolyte Sensing in Human Sweat

Wearable systems embodied as patches could offer noninvasive and real-time solutions for monitoring of biomarkers in human sweat as an alternative to blood testing, with applications in personalized and preventive healthcare. Sweat is considered to be a biofluid of foremost interest for analysis due the numerous biomarkers it contains. Recent studies have demonstrated that the concentration of some of these biomarkers in sweat, such as the electrolytes studied in this work, can be directly correlated to their concentrations in blood, making sweat a trusted biofluid candidate for non-invasive diagnostics. Until now, the biggest impediment to onâbody sweat monitoring was the lack of technology to analyze sweat composition in realâtime and mainly to continuously collect it. The goal of this work was to develop the building blocks of such wearable system for sweat electrolyte monitoring, with main emphasis on the passive microfluidics, the integrated miniaturized quasi-reference electrode and the functionalization of the sensing devices. The basic sensor technology is formed by Ion Sensitive Field Effect Transistors (ISFET) realized in FinFET and ultra-thin body Silicon on Insulator technology. This thesis shows the development of a state-of-the-art microsystem that allows multisensing of pH, Na+, K+ electrolyte concentrations in sweat, with high selectivity and high sensitivities (â50 mV/dec for all electrolytes), in a wearable fashion. The microsystem comprises a biocompatible skin interface that collects even infinitesimal quantities of sweat (of the order of hundreds of picoliters to tenths of nanoliters), which the body produces in periods of low physical effort. One of the main achievements of this work is the integration of Ion Sensing Fully Depleted FETs and zero power consumption microfluidics, enabling low power (less than 50 nWatts/sensor) wearable biosensing. The thesis presents the needed technological processes and optimizations, together with their characterization, in order to achieve a Lab-On-Skin system

Carbon nanotube field-effect sensors for single-molecule detection

This thesis describes a detection system for single molecules based on individual single-walled carbon nanotube field-effect sensors. The sensitivity, spatial confinement and transducer gain of the sensor is derived from a conductance controlled electrochemically created defect, which is also chemically reactive. An automated microfluidic system is designed to enable long and stable measurements of the carbon nanotube device in aqueous environment with temperature control of ±0.1°C. A probe DNA can be covalently attached to the defect through an amide bond and the conductance is modulated when a target DNA binds to the probe. As a result, the conductance shows a traditional random telegraph signal and fluctuates between a hybridized and melted state. By monitoring the conductance as a function of temperature, the kinetics and thermodynamics can be extracted, which are comparable to previous fluorescent correlation spectroscopy studies using optical fluorescent resonant energy transfer. By studying the fluctuation amplitude as a function of charge proximity, buffer concentration and solution potential, it is shown that the sensor is based on a field-effect. The sensor has a temporal resolution of 200 μs and a signal to noise ratio of 3-8 when continuously measuring for 30 seconds. By further reducing the parasitics, the sensor has the capabilities to detect biomolecule kinetics down to microsecond resolution, which could make it an attractive tool for single-molecule experiments with fast kinetics

Functionalization of carbon nanotubes and its application in nanomedicine: A review 1, 2*

ABSTRACT: This review focuses on the latest developments in applications of carbon nanotubes (CNTs) in medicine. A brief history of CNTs and a general introduction to the field are presented. Then, surface modification of CNTs that makes them ideal for use in medical applications is highlighted. Examples of common applications, including cell penetration, drug delivery, gene delivery and imaging, are given. At the same time, there are concerns about their possible adverse effects on human health, since there is evidence that exposure to CNTs induces toxic effects in experimental models. However, CNTs are not a single substance but a growing family of different materials possibly eliciting different biological responses. As a consequence, the hazards associated with the exposure of humans to the different forms of CNTs may be different. Understanding the structure-toxicity relationships would help towards the assessment of the risk related to these materials. Finally, toxicity of CNTs, are discussed. This review article overviews the most recent applications of CNTs in Nanomedicine, covering the period from 1991 to early 2015