Nanogap structures for molecular nanoelectronics

This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps (with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled by a custom hardware and the related software system. The studies were carried out through experiments and simulations of organic molecules, in particular oligothiophenes

Nanogap electrodes for molecular electronics and biosensing

Singlemolecule experiments have been attracting interest since they can pave the way towards the realization of new molecular devices and biosensors. Molecular electronics could be an alternative to classical electronics to overcome the technologic dimensional limit of CMOS technology. On the other hand, biosensor downscaling can open to new detection techniques that are impossible at the conventional dimensional scale. Nowadays, single molecule experiments are mainly based on scanning probe techniques to manipulate and characterize molecules at the nanoscale. Although these techniques have revealed effective tools, real applications are restricted by problems of miniaturization, cost, integration and portability. Nanogap electrodes are an emerging new probing tool for single molecule experiments that can serve a function equivalent to classical probing systems, but guaranteing the integration and portability required in real applications. For these reasons, nanogap electrodes are the object of this thesis, from the fabrication to their employment in molecular electronics and biosensing

Nanogap electrodes for molecular electronics and biosensing

Singlemolecule experiments have been attracting interest since they can pave the way towards the realization of new molecular devices and biosensors. Molecular electronics could be an alternative to classical electronics to overcome the technologic dimensional limit of CMOS technology. On the other hand, biosensor downscaling can open to new detection techniques that are impossible at the conventional dimensional scale. Nowadays, single molecule experiments are mainly based on scanning probe techniques to manipulate and characterize molecules at the nanoscale. Although these techniques have revealed effective tools, real applications are restricted by problems of miniaturization, cost, integration and portability. Nanogap electrodes are an emerging new probing tool for single molecule experiments that can serve a function equivalent to classical probing systems, but guaranteing the integration and portability required in real applications. For these reasons, nanogap electrodes are the object of this thesis, from the fabrication to their employment in molecular electronics and biosensing

A new validation method for modeling nanogap fabrication by electromigration, based on the Resistance–Voltage (R–V ) curve analysis

This Letter presents the validation of a model of electromigration, that is able to simulate nanogap formation by Electromigration Induced Break Junction (EIBJ). To this purpose, a novel validation method was introduced, which is based on the estimation of the deepening atomic flux from a statistical set of Resistance–Voltage (R–V) curves generated during controlled nanogap fabrication. The validation, related to the first cycle of the R–V curves, was successfully performed by observing a high degree of matching between the numerical and experimental atomic fluxes. In addition, the numerical predictions of temperature and density of current were in agreement with the current literature on electromigration. This method is deemed to be useful for providing reliable models of electromigration, which can simulate nanogap formation and become part of the control algorithm in order to improve the process

A 0.13 um CMOS Operational Schmitt Trigger R-to-F Converter for Nanogap-Based Nanosensors Read-Out

We report design and measurements on a 0.13 um CMOS Schmitt Trigger-based quasi-digital resistance-to-fre- quency converter prototype that can be effectively used as a read-out circuit for nanodevice-based sensors. The readout circuit comprises an operational amplifier and an inverting Schmitt Trigger, achieving an hysteresis scaled to 1 mV-order, hence, increasing frequency compared to a standard Schmitt Trigger RC oscillator. Experimental results obtained through an opto-isolated PCB set-up show maximum 0.8%  measurement accuracy and a dynamic range between 50 kOhm and 3 GOhm. The flexible R-to-F converter occupies 0.005 mm2 silicon area and has a simulated power consumption of 142 uW at 1.2 V suppl

Zinc oxide nanowires on customized nanogap chip for high resolution protein nano sensor.

We demonstrate a nano Field Effect Transistor (FET) biosensor using zinc oxide (ZnO) nanowire aligned on gold nanogap electrodes. Nano-FET biosensors are an emerging nanoelectronic technology capable of real-time and label-free quantification of soluble biological molecules. The device consists of a single functionalized ZnO nanowire, as the conducting channel to detect proteins, and of aligned gate electrodes with well-defined nanosized gaps. ZnO were synthesized by hydrothermal reaction and chemically functionalized with amino-propyl groups. We positioned single wires through dielectrophoresis across nanogap electrodes, using a custom platform based on a chip constituted by four nanogaps, thus leading to the parallel positioning and testing of four ZnO wires. Nanogap electrodes with a controlled nanometric separation were ad-hoc fabricated by Electromigration-Induced Break Junction (EIBJ) using a low-cost electronic system. The obtained FETs have a n-type channel and operate in enhancement mode. We have proved the binding of bovine serum albumin (BSA) to demonstrate the effectiveness of the device architecture. The binding was conducted with EDC-amidation reaction among the amine groups of the functionalized ZnO and the carboxyl groups of the protein. The whole process serves as a model system to study in-situ and as a function of time the protein interaction with the ZnO surface.. By dropping a tiny amount of BSA solution with the specific reagents for the EDC-amidation reaction on the ZnO-nanogap chip, we were able to monitor the drain-source current IDS as a function of time. The results showed a constant reduction of the IDS upon protein binding to the ZnO surface, leading to a precise understanding of the protein-surface phenomena. We have also examined the dependence of the IDS as function of the gate voltage VG and we refer to this response as the “device characteristics”. To this end, we devised a novel nano-fabrication method for manufacturing an integrated, high-throughput, multiplexed real-time nano-FET biosensor

An integrated LOC hydrodynamic focuser with a CNN-based camera system for cell counting application

A microfluidic analyzer system and a cell detection algorithm were developed to analyze biomedical fluids. The obtained microfluidic device is based on the integration of dif- ferent fluidic systems: the SensoNor glass/silicon/glass multilayer microchip and ThinXXS plastic slide. A hydrodynamic focuser was designed to sort and analyze cells/particles in a 100μm wide channel. The advantages of this Lab-On-a-Chip (LOC) structure are the easy interfaceability with electrodes and optical systems, biocompatibility and ability of optical analysis and morphologic recognition. The proposed CNN-based (Cellular Neural Network) algorithm is real-time and scalable. This constructed microfluidic and optical system is able to analyze and measure any biological liquid, which contain less than 10μm size particles or cells, and count the number of morphologically well-separated different el- ements in the focused liquid flow using real-time image processing algorithm