1,720,971 research outputs found
Electrical characterization and modeling of pH and microparticle nanoelectronic sensors
Full text linkBy 2050, the world’s population will have risen to 9.7 billion, with 2 billion over the age of 60. To face this situation the actual healthcare system must be improved and innovated.
One way to achieve this is to invest in technology.
Already today, advancements in biology, chemistry and medicine are being enabled
by devices, tools and instrumentation powered by existing micro- and nanoelectronics;
nevertheless the potential of these technologies is still far from being fully developed.
In fact, recent years have seen a growing attention toward novel and interdisciplinary research fields at the frontier between life sciences and engineering. One clear example is the area of bioelectronics, which holds the potential to revolutionize, among others, our approach to healthcare.
Electronics and the semiconductor industry are sufficiently mature to offer and support a huge variety of solutions, going from the enormous data centers to collect the clinical data of the patients and perform accurate analysis, the ability to provide portable systems equipped with biosensors for point-of-care diagnosis and treatments, and the nanotechnologies and nanobiosensors enabling the so- called personalized medicine and
the next-generation of devices for research purposes.
Technology innovation and the development of the next-generation bioelectronic sensors require deep understanding of new phenomena and must necessarily pass through a phase of research, design, optimization, and characterization. Accurate numerical and
analytical models to predict the transduction performances and the reliability of a new biosensor concept play a role of utmost importance in supporting all of the above.
My thesis falls in this realm.
In particular, I focused on the modeling and characterization of ion-sensitive field-effect-transistors (ISFETs) made of silicon nanoribbons. The concept of ISFET, developed in the early 1970’s, has re-gained increasing attention in the last decade thanks to its flexibility in sensing different types of analytes and due to its compatibility with the CMOS fabrication process. The research activity was focused in two directions: (i) ISFET characterization with experiments performed in dry and liquid electrolyte environments, and (ii) simulations performed with commercial (Sentaurus TCAD) and in-house developed tools (ENBIOS). Existing simulation tools have been extended and improved to account for surface reactions. We modeled and characterized the pH-sensitivity in DC conditions, and we developed a quasi-3D model for the AC response of nanoribbons to dielectric microbeads in liquid environment. The measurements were performed during a stage at the CLSE laboratory at EPFL (Lausanne, CH), whereas the measurements of the nanoribbons in dry were performed at the University of Udine. Original contributions in this area regard the characterization of signal-to-noise ratio (SNR) in nanoribbon ISFETs and the study of the SNR scaling with the nanoribbon architecture and dimensions.
Besides ISFETs, we studied the AC response of electrolyte/insulator/semiconductor
samples. The insulator surface was functionalized with a self-assembled-monolayer for the detection of specific molecules. We developed a compact model that is extremely useful to analyze the electrical properties of each part composing the sample and gives useful indications for the realization of a full sensor for the detection of DNA/PNA at the insulator/electrolyte surface. Original contributions in this area regard the development of a compact model capable of detecting different PNA orientations attached on the sensor surface.
As a last activity, the thesis describes the publication of two simulation tools on the nanohub.org portal. The tools are based on ENBIOS, include DC and AC the surface reaction models developed during the PhD and represent a useful reference for researchers and scholars interested to explore the potential of the ISFET sensing concept
Detecting microparticles and their charge-state by nanoribbon sensors and physical modeling
No full textIn the last decade, CMOS nano FETs have attracted increasing interest as sensing devices for impedance spectroscopy of biomolecules [1]. In this context, we present a quantitative numerical analysis of dielectric microbead detection and charge-state discrimination experiments with nanoribbon (NR) FETs operated in the frequency domain up to 1 MHz
Derivation and Numerical Verification of a Compact Analytical Model for the AC Admittance Response of Nanoelectrodes, Suitable for the Analysis and Optimization of Impedance Biosensors
No full textThis paper presents a compact analytical model for the AC response of nanoelectrode-based impedimetric biosensors to dielectric nanoparticles suspended in the electrolyte. The model highlights the functional dependence of the impedance change on the nanoparticle and the system geometrical and physical parameters. The model is carefully verified by means of 2-D simulations carried out with an ad hoc numerical solver of the Poisson–Nernst–Planck (Poisson-Drift-Diffusion) equations. The results can be useful to determine optimum detection conditions for impedimetric nanobiosensors, and to interpret experimental results
ENBIOS-2D Lab
No full textENBIOS-2D Lab is a tool to illustrate and to study simple Ion Sensitive Field Effect Transistor structures in two dimensions. Together with its companion tool ENBIOS-1D Lab, it is meant for use as a teaching tool in support of undergraduate or graduate courses on the basic physics of transduction in ion and particle sensors, and to assist early stage researchers getting familiar with some basic concepts in the field.
At the present stage, ENBIOS-2D Lab supports simulation and visualization of DC I-V characteristics, impedance/admittance spectra as well as DC and AC potential/carrier/ion distributions in simple two-dimensional ISFET structures. A broader set of case studies will become available with future releases of the tool.
The companion ENBIOS-1D Lab tool offers the possibility to simulate simple Electrolyte/Insulator/Semiconductor systems in one-dimension.
The physical system is modelled with the Poisson/Boltzmann (DC) and Poisson/Nernst/Planck - Poisson/Drift/Diffusion (AC small signal) equations coupled to the site-binding charge model equations at the Electrolyte/Insulator interfaces. Dedicated models are implemented for the frequency and salinity dependence of the electrolyte electrical permittivity and the temperature dependence of the ions' mobility (in water solvent).
ENBIOS-2D Lab is powered by ENBIOS, (Electronic Nano-BIOsensor Simulator), a general purpose three-dimensional Control Volume Finite Element Method (CVFEM) simulator developed in-house at the University of Udine - Italy. ENBIOS simulates in three dimensions (3D) the DC and AC small signal impedance response to ions and micro/nanoparticles of three-dimensional devices made of semiconductor, insulator and electrolyte materials
Models for the use of commercial TCAD in the analysis of silicon-based integrated biosensors
No full textWe present a simple approach to describe electrolytes in TCAD simulators for the modeling of nano-biosensors. The method exploits the similarity between the transport equations for electrons and holes in semiconductors and the ones for charged ions in a solution. We describe a few workarounds to improve the model accuracy in spite of the limitations of commercial TCAD. Applications to the simulations of silicon nanowire and nanoelectrode biosensors are reported as relevant examples
Analysis of Dielectric Microbead Detection by Impedance Spectroscopy with Nanoribbons
No full textWe present a quantitative numerical analysis of dielectric microbead detection experiments with nanoribbons operated in the AC small signal regime. To this purpose, a comprehensive model of nanoribbon operation in electrolyte environment and with DC/AC signals is extended to include the effect of site-binding charges in DC, transient and AC conditions. The model is calibrated against DC measurements and pH-transients data from the literature. The impact of the microfluidic chamber size, the interconnects and the site-binding charge is investigated. The calibrated model suggests that the impedance response to micron-sized beads cannot be explained without also taking into account the bead surface charge
Modeling and Simulation of Small CCMV Virus Detection by means of High Frequency Impedance Spectroscopy at Nanoelectrodes
No full textWe present an electrical model for the high frequency impedance spectroscopy (HFIS) response of nanoelectrodes to CCMV capsids and full virus biomolecules. The virus electrical and geometrical parameters are extracted from available atomistic descriptions. Simulations of the response at a realistic HFIS CMOS platform suggest that the frequency of optimum sensitivity is within reach of existing designs. Furthermore, they shed light on the role of virus charge and ionic strength on the expected signal. The detection of single viruses could be possible with decananometer scale electrodes operated in optimal conditions and low-noise readout circuitry. © 2017 IEEE
ENBIOS-1D Lab
No full textENBIOS-1D Lab is a tool to illustrate and to study simple Electrolyte, Electrolyte/Insulator and /Electrolyte/Insulator/Semiconductor systems in one dimension. It is meant for use as a teaching tool in support of undergraduate or graduate courses on the basic physics of transduction in ion and particle sensors, and to assist early stage researchers getting familiar with some basic concepts in the field.
At the present stage, ENBIOS-1D Lab supports simulation and visualization of impedance/admittance spectra as well as DC and AC potential/ion distributions in simple one-dimensional Electrolyte (E), Electrolyte/Insulator (EI) and Electrolyte/Insulator/Semiconductor (EIS) systems. A broader set of case studies will become available with future releases of the tool, possibly including Ion Sensitive Field Effect Transistor (ISFET) and Nanoelectrode array devices.
The physical systems are modelled with the Poisson/Boltzmann (DC) and Poisson/Nernst/Planck - Poisson/Drift/Diffusion (AC small signal) equations. Dedicated models are implemented for the build up of site-binding charge at Electrolyte/Insulator interfaces and for the frequency and salinity dependence of the electrolyte electrical permittivity.
ENBIOS-1D Lab is powered by ENBIOS, (Electronic Nano-BIOsensor Simulator), a general purpose three-dimensional Control Volume Finite Element Method (CVFEM) simulator developed in-house at the University of Udine - Italy. ENBIOS simulates in three dimensions (3D) the DC and AC small signal impedance response to ions and micro/nanoparticles of three-dimensional devices made of semiconductor, insulator and electrolyte materials
Technological development of high-k dielectric FinFETs for liquid environment
No full textThis work presents the technological development and characterization of n-channel fully depleted high-k dielectric FinFETs (Fin Field Effect Transistor) for applications in a liquid environment. Herein, we provide a systematic approach based on Finite Element Analysis for a high-control fabrication process of vertical Si-fins on bulk and we provide many useful fabrication expedients. Metal gate FinFETs have been successfully electrically characterized, showing excellent subthreshold slope SS = 72 mV/dec and high Ion/Ioff
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